Fossil

#define MODE_EQP     12  /* Converts EXPLAIN QUERY PLAN output into a graph */
#define MODE_Json    13  /* Output JSON */
#define MODE_Markdown 14 /* Markdown formatting */
#define MODE_Table   15  /* MySQL-style table formatting */
#define MODE_Box     16  /* Unicode box-drawing characters */
#define MODE_Count   17  /* Output only a count of the rows of output */
#define MODE_Off     18  /* No query output shown */
#define MODE_ScanExp 19  /* Like MODE_Explain, but for ".scanstats vm" */

static const char *modeDescr[] = {
  "line",
  "column",
  "list",
  "semi",
  "html",

      if( p->cnt++>0 ) utf8_printf(p->out, "%s", p->rowSeparator);
      for(i=0; i<nArg; i++){
        utf8_printf(p->out,"%*s = %s%s", w, azCol[i],
                azArg[i] ? azArg[i] : p->nullValue, p->rowSeparator);
      }
      break;
    }
    case MODE_ScanExp:
    case MODE_Explain: {
      static const int aExplainWidth[] = {4,       13, 4, 4, 4, 13, 2, 13};
      static const int aExplainMap[] =   {0,       1,  2, 3, 4, 5,  6, 7 };
      static const int aScanExpWidth[] = {4, 6, 6, 13, 4, 4, 4, 13, 2, 13};
      static const int aScanExpMap[] =   {0, 9, 8, 1,  2, 3, 4, 5,  6, 7 };

      const int *aWidth = aExplainWidth;
      const int *aMap = aExplainMap;
      int nWidth = ArraySize(aExplainWidth);
      int iIndent = 1;

      if( p->cMode==MODE_ScanExp ){
        aWidth = aScanExpWidth;
        aMap = aScanExpMap;
        nWidth = ArraySize(aScanExpWidth);
        iIndent = 3;
      }
      if( nArg>nWidth ) nArg = nWidth;

      /* If this is the first row seen, print out the headers */
      if( p->cnt++==0 ){
        for(i=0; i<nArg; i++){

          utf8_width_print(p->out, aWidth[i], azCol[ aMap[i] ]);
          fputs(i==nArg-1 ? "\n" : "  ", p->out);
        }
        for(i=0; i<nArg; i++){

          print_dashes(p->out, aWidth[i]);
          fputs(i==nArg-1 ? "\n" : "  ", p->out);
        }
      }

      /* If there is no data, exit early. */
      if( azArg==0 ) break;

      for(i=0; i<nArg; i++){
        const char *zSep = "  ";
        int w = aWidth[i];
        const char *zVal = azArg[ aMap[i] ];
        if( i==nArg-1 ) w = 0;
        if( zVal && strlenChar(zVal)>w ){
          w = strlenChar(zVal);
          zSep = " ";
        }
        if( i==iIndent && p->aiIndent && p->pStmt ){
          if( p->iIndent<p->nIndent ){
            utf8_printf(p->out, "%*.s", p->aiIndent[p->iIndent], "");
          }
          p->iIndent++;
        }
        utf8_width_print(p->out, w, zVal ? zVal : p->nullValue);
        fputs(i==nArg-1 ? "\n" : zSep, p->out);
      }
      break;
    }
    case MODE_Semi: {   /* .schema and .fullschema output */
      printSchemaLine(p->out, azArg[0], ";\n");
      break;
    }

    }
    ret++;
  }
  return ret;
}
#endif




#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
static void display_explain_scanstats(
  sqlite3 *db,                    /* Database to query */
  ShellState *pArg                /* Pointer to ShellState */
){




  static const int f = SQLITE_SCANSTAT_COMPLEX;
  sqlite3_stmt *p = pArg->pStmt;
  int ii = 0;
  i64 nTotal = 0;
  int nWidth = 0;
  eqp_reset(pArg);

    }

    eqp_append(pArg, iId, iPid, zText);
    sqlite3_free(zText);
  }

  eqp_render(pArg, nTotal);
}
#endif


/*
** Parameter azArray points to a zero-terminated array of strings. zStr
** points to a single nul-terminated string. Return non-zero if zStr
** is equal, according to strcmp(), to any of the strings in the array.
** Otherwise, return zero.
*/

**       and ends on one of:
**          Yield  SeekGt  SeekLt  RowSetRead  Rewind
**       or if the P1 parameter is one instead of zero,
**       then indent all opcodes between the earlier instruction
**       and "Goto" by 2 spaces.
*/
static void explain_data_prepare(ShellState *p, sqlite3_stmt *pSql){


  int *abYield = 0;               /* True if op is an OP_Yield */
  int nAlloc = 0;                 /* Allocated size of p->aiIndent[], abYield */
  int iOp;                        /* Index of operation in p->aiIndent[] */

  const char *azNext[] = { "Next", "Prev", "VPrev", "VNext", "SorterNext",
                           "Return", 0 };
  const char *azYield[] = { "Yield", "SeekLT", "SeekGT", "RowSetRead",
                            "Rewind", 0 };
  const char *azGoto[] = { "Goto", 0 };

  /* The caller guarantees that the leftmost 4 columns of the statement
  ** passed to this function are equivalent to the leftmost 4 columns
  ** of EXPLAIN statement output. In practice the statement may be

  ** an EXPLAIN, or it may be a query on the bytecode() virtual table.  */
  assert( sqlite3_column_count(pSql)>=4 );



  assert( 0==sqlite3_stricmp( sqlite3_column_name(pSql, 0), "addr" ) );
  assert( 0==sqlite3_stricmp( sqlite3_column_name(pSql, 1), "opcode" ) );
  assert( 0==sqlite3_stricmp( sqlite3_column_name(pSql, 2), "p1" ) );

  assert( 0==sqlite3_stricmp( sqlite3_column_name(pSql, 3), "p2" ) );




  for(iOp=0; SQLITE_ROW==sqlite3_step(pSql); iOp++){
    int i;
    int iAddr = sqlite3_column_int(pSql, 0);
    const char *zOp = (const char*)sqlite3_column_text(pSql, 1);
    int p1 = sqlite3_column_int(pSql, 2);
    int p2 = sqlite3_column_int(pSql, 3);


    /* Assuming that p2 is an instruction address, set variable p2op to the
    ** index of that instruction in the aiIndent[] array. p2 and p2op may be
    ** different if the current instruction is part of a sub-program generated
    ** by an SQL trigger or foreign key.  */

    int p2op = (p2 + (iOp-iAddr));

    /* Grow the p->aiIndent array as required */
    if( iOp>=nAlloc ){














      nAlloc += 100;
      p->aiIndent = (int*)sqlite3_realloc64(p->aiIndent, nAlloc*sizeof(int));
      shell_check_oom(p->aiIndent);
      abYield = (int*)sqlite3_realloc64(abYield, nAlloc*sizeof(int));
      shell_check_oom(abYield);
    }

    abYield[iOp] = str_in_array(zOp, azYield);
    p->aiIndent[iOp] = 0;
    p->nIndent = iOp+1;

    if( str_in_array(zOp, azNext) && p2op>0 ){
      for(i=p2op; i<iOp; i++) p->aiIndent[i] += 2;
    }
    if( str_in_array(zOp, azGoto) && p2op<iOp && (abYield[p2op] || p1) ){


      for(i=p2op; i<iOp; i++) p->aiIndent[i] += 2;
    }
  }

  p->iIndent = 0;
  sqlite3_free(abYield);
  sqlite3_reset(pSql);
}

/*
** Free the array allocated by explain_data_prepare().
*/
static void explain_data_delete(ShellState *p){
  sqlite3_free(p->aiIndent);
  p->aiIndent = 0;
  p->nIndent = 0;
  p->iIndent = 0;
}

static void exec_prepared_stmt(ShellState*, sqlite3_stmt*);

/*
** Display scan stats.
*/
static void display_scanstats(
  sqlite3 *db,                    /* Database to query */
  ShellState *pArg                /* Pointer to ShellState */
){
#ifndef SQLITE_ENABLE_STMT_SCANSTATUS
  UNUSED_PARAMETER(db);
  UNUSED_PARAMETER(pArg);
#else
  if( pArg->scanstatsOn==3 ){
    const char *zSql = 
      "  SELECT addr, opcode, p1, p2, p3, p4, p5, comment, nexec,"
      "   round(ncycle*100.0 / (sum(ncycle) OVER ()), 2)||'%' AS cycles"
      "   FROM bytecode(?)";

    int rc = SQLITE_OK;
    sqlite3_stmt *pStmt = 0;
    rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
    if( rc==SQLITE_OK ){
      sqlite3_stmt *pSave = pArg->pStmt;
      pArg->pStmt = pStmt;
      sqlite3_bind_pointer(pStmt, 1, pSave, "stmt-pointer", 0);

      pArg->cnt = 0;
      pArg->cMode = MODE_ScanExp;
      explain_data_prepare(pArg, pStmt);
      exec_prepared_stmt(pArg, pStmt);
      explain_data_delete(pArg);

      sqlite3_finalize(pStmt);
      pArg->pStmt = pSave;
    }
  }else{
    display_explain_scanstats(db, pArg);
  }
#endif
}

/*
** Disable and restore .wheretrace and .treetrace/.selecttrace settings.
*/
static unsigned int savedSelectTrace;
static unsigned int savedWhereTrace;
static void disable_debug_trace_modes(void){

        pArg->pStmt = pStmt;
        pArg->cnt = 0;
      }

      /* Show the EXPLAIN QUERY PLAN if .eqp is on */
      if( pArg && pArg->autoEQP && sqlite3_stmt_isexplain(pStmt)==0 ){
        sqlite3_stmt *pExplain;

        int triggerEQP = 0;
        disable_debug_trace_modes();
        sqlite3_db_config(db, SQLITE_DBCONFIG_TRIGGER_EQP, -1, &triggerEQP);
        if( pArg->autoEQP>=AUTOEQP_trigger ){
          sqlite3_db_config(db, SQLITE_DBCONFIG_TRIGGER_EQP, 1, 0);
        }
        pExplain = pStmt;
        sqlite3_reset(pExplain);

        rc = sqlite3_stmt_explain(pExplain, 2);
        if( rc==SQLITE_OK ){
          while( sqlite3_step(pExplain)==SQLITE_ROW ){
            const char *zEQPLine = (const char*)sqlite3_column_text(pExplain,3);
            int iEqpId = sqlite3_column_int(pExplain, 0);
            int iParentId = sqlite3_column_int(pExplain, 1);
            if( zEQPLine==0 ) zEQPLine = "";
            if( zEQPLine[0]=='-' ) eqp_render(pArg, 0);
            eqp_append(pArg, iEqpId, iParentId, zEQPLine);
          }
          eqp_render(pArg, 0);
        }


        if( pArg->autoEQP>=AUTOEQP_full ){
          /* Also do an EXPLAIN for ".eqp full" mode */
          sqlite3_reset(pExplain);

          rc = sqlite3_stmt_explain(pExplain, 1);
          if( rc==SQLITE_OK ){
            pArg->cMode = MODE_Explain;
            assert( sqlite3_stmt_isexplain(pExplain)==1 );
            explain_data_prepare(pArg, pExplain);
            exec_prepared_stmt(pArg, pExplain);
            explain_data_delete(pArg);
          }


        }
        if( pArg->autoEQP>=AUTOEQP_trigger && triggerEQP==0 ){
          sqlite3_db_config(db, SQLITE_DBCONFIG_TRIGGER_EQP, 0, 0);




        }
        sqlite3_reset(pStmt);
        sqlite3_stmt_explain(pStmt, 0);
        restore_debug_trace_modes();
      }

      if( pArg ){
        int bIsExplain = (sqlite3_stmt_isexplain(pStmt)==1);
        pArg->cMode = pArg->mode;
        if( pArg->autoExplain ){
          if( bIsExplain ){
            pArg->cMode = MODE_Explain;
          }
          if( sqlite3_stmt_isexplain(pStmt)==2 ){
            pArg->cMode = MODE_EQP;
          }
        }

        /* If the shell is currently in ".explain" mode, gather the extra
        ** data required to add indents to the output.*/
        if( pArg->cMode==MODE_Explain && bIsExplain ){
          explain_data_prepare(pArg, pStmt);
        }
      }

      bind_prepared_stmt(pArg, pStmt);
      exec_prepared_stmt(pArg, pStmt);
      explain_data_delete(pArg);

    }
    close_db(pSrc);
  }else
#endif /* !defined(SQLITE_SHELL_FIDDLE) */

  if( c=='s' && cli_strncmp(azArg[0], "scanstats", n)==0 ){
    if( nArg==2 ){
      if( cli_strcmp(azArg[1], "vm")==0 ){
        p->scanstatsOn = 3;
      }else
      if( cli_strcmp(azArg[1], "est")==0 ){
        p->scanstatsOn = 2;
      }else{
        p->scanstatsOn = (u8)booleanValue(azArg[1]);
      }
      open_db(p, 0);
      sqlite3_db_config(

** the text of this file.  Search for "Begin file sqlite3.h" to find the start
** of the embedded sqlite3.h header file.) Additional code files may be needed
** if you want a wrapper to interface SQLite with your choice of programming
** language. The code for the "sqlite3" command-line shell is also in a
** separate file. This file contains only code for the core SQLite library.
**
** The content in this amalgamation comes from Fossil check-in
** a0b9aecbaca9a8e784fd2bcb50f78cbdcf4.
*/
#define SQLITE_CORE 1
#define SQLITE_AMALGAMATION 1
#ifndef SQLITE_PRIVATE
# define SQLITE_PRIVATE static
#endif
/************** Begin file sqliteInt.h ***************************************/

**
** See also: [sqlite3_libversion()],
** [sqlite3_libversion_number()], [sqlite3_sourceid()],
** [sqlite_version()] and [sqlite_source_id()].
*/
#define SQLITE_VERSION        "3.43.0"
#define SQLITE_VERSION_NUMBER 3043000
#define SQLITE_SOURCE_ID      "2023-08-02 16:06:02 ea0b9aecbaca9a8e784fd2bcb50f78cbdcf4c5cfb45a7700bb222e4cc104c644"

/*
** CAPI3REF: Run-Time Library Version Numbers
** KEYWORDS: sqlite3_version sqlite3_sourceid
**
** These interfaces provide the same information as the [SQLITE_VERSION],
** [SQLITE_VERSION_NUMBER], and [SQLITE_SOURCE_ID] C preprocessor macros

** prepared statement S is an EXPLAIN statement, or 2 if the
** statement S is an EXPLAIN QUERY PLAN.
** ^The sqlite3_stmt_isexplain(S) interface returns 0 if S is
** an ordinary statement or a NULL pointer.
*/
SQLITE_API int sqlite3_stmt_isexplain(sqlite3_stmt *pStmt);

/*
** CAPI3REF: Change The EXPLAIN Setting For A Prepared Statement
** METHOD: sqlite3_stmt
**
** The sqlite3_stmt_explain(S,E) interface changes the EXPLAIN
** setting for [prepared statement] S.  If E is zero, then S becomes
** a normal prepared statement.  If E is 1, then S behaves as if
** its SQL text began with "[EXPLAIN]".  If E is 2, then S behaves as if
** its SQL text began with "[EXPLAIN QUERY PLAN]".
**
** Calling sqlite3_stmt_explain(S,E) might cause S to be reprepared.
** SQLite tries to avoid a reprepare, but a reprepare might be necessary
** on the first transition into EXPLAIN or EXPLAIN QUERY PLAN mode.
**
** Because of the potential need to reprepare, a call to
** sqlite3_stmt_explain(S,E) will fail with SQLITE_ERROR if S cannot be
** reprepared because it was created using [sqlite3_prepare()] instead of
** the newer [sqlite3_prepare_v2()] or [sqlite3_prepare_v3()] interfaces and
** hence has no saved SQL text with which to reprepare.
**
** Changing the explain setting for a prepared statement does not change
** the original SQL text for the statement.  Hence, if the SQL text originally
** began with EXPLAIN or EXPLAIN QUERY PLAN, but sqlite3_stmt_explain(S,0)
** is called to convert the statement into an ordinary statement, the EXPLAIN
** or EXPLAIN QUERY PLAN keywords will still appear in the sqlite3_sql(S)
** output, even though the statement now acts like a normal SQL statement.
**
** This routine returns SQLITE_OK if the explain mode is successfully
** changed, or an error code if the explain mode could not be changed.
** The explain mode cannot be changed while a statement is active.
** Hence, it is good practice to call [sqlite3_reset(S)]
** immediately prior to calling sqlite3_stmt_explain(S,E).
*/
SQLITE_API int sqlite3_stmt_explain(sqlite3_stmt *pStmt, int eMode);

/*
** CAPI3REF: Determine If A Prepared Statement Has Been Reset
** METHOD: sqlite3_stmt
**
** ^The sqlite3_stmt_busy(S) interface returns true (non-zero) if the
** [prepared statement] S has been stepped at least once using
** [sqlite3_step(S)] but has neither run to completion (returned

** The SQLITE_WITHIN(P,S,E) macro checks to see if pointer P points to
** something between S (inclusive) and E (exclusive).
**
** In other words, S is a buffer and E is a pointer to the first byte after
** the end of buffer S.  This macro returns true if P points to something
** contained within the buffer S.
*/
#define SQLITE_WITHIN(P,S,E)   (((uptr)(P)>=(uptr)(S))&&((uptr)(P)<(uptr)(E)))

/*
** P is one byte past the end of a large buffer. Return true if a span of bytes
** between S..E crosses the end of that buffer.  In other words, return true
** if the sub-buffer S..E-1 overflows the buffer show last byte is P-1.
**
** S is the start of the span.  E is one byte past the end of end of span.
**
**                        P
**     |-----------------|                FALSE
**               |-------|
**               S        E
**
**                        P
**     |-----------------|
**                    |-------|           TRUE
**                    S        E
**
**                        P
**     |-----------------|
**                        |-------|       FALSE
**                        S        E
*/
#define SQLITE_OVERFLOW(P,S,E) (((uptr)(S)<(uptr)(P))&&((uptr)(E)>(uptr)(P)))

/*
** Macros to determine whether the machine is big or little endian,
** and whether or not that determination is run-time or compile-time.
**
** For best performance, an attempt is made to guess at the byte-order
** using C-preprocessor macros.  If that is unsuccessful, or if

typedef struct Module Module;
typedef struct NameContext NameContext;
typedef struct OnOrUsing OnOrUsing;
typedef struct Parse Parse;
typedef struct ParseCleanup ParseCleanup;
typedef struct PreUpdate PreUpdate;
typedef struct PrintfArguments PrintfArguments;
typedef struct RCStr RCStr;
typedef struct RenameToken RenameToken;
typedef struct Returning Returning;
typedef struct RowSet RowSet;
typedef struct Savepoint Savepoint;
typedef struct Select Select;
typedef struct SQLiteThread SQLiteThread;
typedef struct SelectDest SelectDest;

SQLITE_PRIVATE int sqlite3BtreeLast(BtCursor*, int *pRes);
SQLITE_PRIVATE int sqlite3BtreeNext(BtCursor*, int flags);
SQLITE_PRIVATE int sqlite3BtreeEof(BtCursor*);
SQLITE_PRIVATE int sqlite3BtreePrevious(BtCursor*, int flags);
SQLITE_PRIVATE i64 sqlite3BtreeIntegerKey(BtCursor*);
SQLITE_PRIVATE void sqlite3BtreeCursorPin(BtCursor*);
SQLITE_PRIVATE void sqlite3BtreeCursorUnpin(BtCursor*);

SQLITE_PRIVATE i64 sqlite3BtreeOffset(BtCursor*);

SQLITE_PRIVATE int sqlite3BtreePayload(BtCursor*, u32 offset, u32 amt, void*);
SQLITE_PRIVATE const void *sqlite3BtreePayloadFetch(BtCursor*, u32 *pAmt);
SQLITE_PRIVATE u32 sqlite3BtreePayloadSize(BtCursor*);
SQLITE_PRIVATE sqlite3_int64 sqlite3BtreeMaxRecordSize(BtCursor*);

SQLITE_PRIVATE int sqlite3BtreeIntegrityCheck(
  sqlite3 *db,  /* Database connection that is running the check */

#define SQLITE_BalancedMerge  0x00200000 /* Balance multi-way merges */
#define SQLITE_ReleaseReg     0x00400000 /* Use OP_ReleaseReg for testing */
#define SQLITE_FlttnUnionAll  0x00800000 /* Disable the UNION ALL flattener */
   /* TH3 expects this value  ^^^^^^^^^^ See flatten04.test */
#define SQLITE_IndexedExpr    0x01000000 /* Pull exprs from index when able */
#define SQLITE_Coroutines     0x02000000 /* Co-routines for subqueries */
#define SQLITE_NullUnusedCols 0x04000000 /* NULL unused columns in subqueries */
#define SQLITE_OnePass        0x08000000 /* Single-pass DELETE and UPDATE */
#define SQLITE_AllOpts        0xffffffff /* All optimizations */

/*
** Macros for testing whether or not optimizations are enabled or disabled.
*/
#define OptimizationDisabled(db, mask)  (((db)->dbOptFlags&(mask))!=0)
#define OptimizationEnabled(db, mask)   (((db)->dbOptFlags&(mask))==0)

  Table *pTriggerTab;  /* Table triggers are being coded for */
  TriggerPrg *pTriggerPrg;  /* Linked list of coded triggers */
  ParseCleanup *pCleanup;   /* List of cleanup operations to run after parse */
  union {
    int addrCrTab;         /* Address of OP_CreateBtree on CREATE TABLE */
    Returning *pReturning; /* The RETURNING clause */
  } u1;
  LogEst nQueryLoop;   /* Est number of iterations of a query (10*log2(N)) */
  u32 oldmask;         /* Mask of old.* columns referenced */
  u32 newmask;         /* Mask of new.* columns referenced */
#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
  u32 nProgressSteps;  /* xProgress steps taken during sqlite3_prepare() */
#endif
  u8 eTriggerOp;       /* TK_UPDATE, TK_INSERT or TK_DELETE */
  u8 bReturning;       /* Coding a RETURNING trigger */

};
#define SQLITE_PRINTF_INTERNAL 0x01  /* Internal-use-only converters allowed */
#define SQLITE_PRINTF_SQLFUNC  0x02  /* SQL function arguments to VXPrintf */
#define SQLITE_PRINTF_MALLOCED 0x04  /* True if xText is allocated space */

#define isMalloced(X)  (((X)->printfFlags & SQLITE_PRINTF_MALLOCED)!=0)

/*
** The following object is the header for an "RCStr" or "reference-counted
** string".  An RCStr is passed around and used like any other char*
** that has been dynamically allocated.  The important interface
** differences:
**
**   1.  RCStr strings are reference counted.  They are deallocated
**       when the reference count reaches zero.
**
**   2.  Use sqlite3RCStrUnref() to free an RCStr string rather than
**       sqlite3_free()
**
**   3.  Make a (read-only) copy of a read-only RCStr string using
**       sqlite3RCStrRef().
*/
struct RCStr {
  u64 nRCRef;            /* Number of references */
  /* Total structure size should be a multiple of 8 bytes for alignment */
};

/*
** A pointer to this structure is used to communicate information
** from sqlite3Init and OP_ParseSchema into the sqlite3InitCallback.
*/
typedef struct {
  sqlite3 *db;        /* The database being initialized */

SQLITE_PRIVATE void sqlite3FileSuffix3(const char*, char*);
#else
# define sqlite3FileSuffix3(X,Y)
#endif
SQLITE_PRIVATE u8 sqlite3GetBoolean(const char *z,u8);

SQLITE_PRIVATE const void *sqlite3ValueText(sqlite3_value*, u8);
SQLITE_PRIVATE int sqlite3ValueIsOfClass(const sqlite3_value*, void(*)(void*));
SQLITE_PRIVATE int sqlite3ValueBytes(sqlite3_value*, u8);
SQLITE_PRIVATE void sqlite3ValueSetStr(sqlite3_value*, int, const void *,u8,
                        void(*)(void*));
SQLITE_PRIVATE void sqlite3ValueSetNull(sqlite3_value*);
SQLITE_PRIVATE void sqlite3ValueFree(sqlite3_value*);
#ifndef SQLITE_UNTESTABLE
SQLITE_PRIVATE void sqlite3ResultIntReal(sqlite3_context*);

);
SQLITE_PRIVATE void sqlite3NoopDestructor(void*);
SQLITE_PRIVATE void *sqlite3OomFault(sqlite3*);
SQLITE_PRIVATE void sqlite3OomClear(sqlite3*);
SQLITE_PRIVATE int sqlite3ApiExit(sqlite3 *db, int);
SQLITE_PRIVATE int sqlite3OpenTempDatabase(Parse *);

SQLITE_PRIVATE char *sqlite3RCStrRef(char*);
SQLITE_PRIVATE void sqlite3RCStrUnref(char*);
SQLITE_PRIVATE char *sqlite3RCStrNew(u64);
SQLITE_PRIVATE char *sqlite3RCStrResize(char*,u64);

SQLITE_PRIVATE void sqlite3StrAccumInit(StrAccum*, sqlite3*, char*, int, int);
SQLITE_PRIVATE int sqlite3StrAccumEnlarge(StrAccum*, i64);
SQLITE_PRIVATE char *sqlite3StrAccumFinish(StrAccum*);
SQLITE_PRIVATE void sqlite3StrAccumSetError(StrAccum*, u8);
SQLITE_PRIVATE void sqlite3ResultStrAccum(sqlite3_context*,StrAccum*);
SQLITE_PRIVATE void sqlite3SelectDestInit(SelectDest*,int,int);
SQLITE_PRIVATE Expr *sqlite3CreateColumnExpr(sqlite3 *, SrcList *, int, int);

/* Opaque type used by code in vdbesort.c */
typedef struct VdbeSorter VdbeSorter;

/* Elements of the linked list at Vdbe.pAuxData */
typedef struct AuxData AuxData;

/* A cache of large TEXT or BLOB values in a VdbeCursor */
typedef struct VdbeTxtBlbCache VdbeTxtBlbCache;

/* Types of VDBE cursors */
#define CURTYPE_BTREE       0
#define CURTYPE_SORTER      1
#define CURTYPE_VTAB        2
#define CURTYPE_PSEUDO      3

/*

  u8 seekOp;              /* Most recent seek operation on this cursor */
  u8 wrFlag;              /* The wrFlag argument to sqlite3BtreeCursor() */
#endif
  Bool isEphemeral:1;     /* True for an ephemeral table */
  Bool useRandomRowid:1;  /* Generate new record numbers semi-randomly */
  Bool isOrdered:1;       /* True if the table is not BTREE_UNORDERED */
  Bool noReuse:1;         /* OpenEphemeral may not reuse this cursor */
  Bool colCache:1;        /* pCache pointer is initialized and non-NULL */
  u16 seekHit;            /* See the OP_SeekHit and OP_IfNoHope opcodes */
  union {                 /* pBtx for isEphermeral.  pAltMap otherwise */
    Btree *pBtx;            /* Separate file holding temporary table */
    u32 *aAltMap;           /* Mapping from table to index column numbers */
  } ub;
  i64 seqCount;           /* Sequence counter */

  u32 *aOffset;           /* Pointer to aType[nField] */
  const u8 *aRow;         /* Data for the current row, if all on one page */
  u32 payloadSize;        /* Total number of bytes in the record */
  u32 szRow;              /* Byte available in aRow */
#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
  u64 maskUsed;           /* Mask of columns used by this cursor */
#endif
  VdbeTxtBlbCache *pCache; /* Cache of large TEXT or BLOB values */

  /* 2*nField extra array elements allocated for aType[], beyond the one
  ** static element declared in the structure.  nField total array slots for
  ** aType[] and nField+1 array slots for aOffset[] */
  u32 aType[1];           /* Type values record decode.  MUST BE LAST */
};

/* Return true if P is a null-only cursor
*/
#define IsNullCursor(P) \
  ((P)->eCurType==CURTYPE_PSEUDO && (P)->nullRow && (P)->seekResult==0)


/*
** A value for VdbeCursor.cacheStatus that means the cache is always invalid.
*/
#define CACHE_STALE 0

/*
** Large TEXT or BLOB values can be slow to load, so we want to avoid
** loading them more than once.  For that reason, large TEXT and BLOB values
** can be stored in a cache defined by this object, and attached to the
** VdbeCursor using the pCache field.
*/
struct VdbeTxtBlbCache {
  char *pCValue;        /* A RCStr buffer to hold the value */
  i64 iOffset;          /* File offset of the row being cached */
  int iCol;             /* Column for which the cache is valid */
  u32 cacheStatus;      /* Vdbe.cacheCtr value */
  u32 colCacheCtr;      /* Column cache counter */
};

/*
** When a sub-program is executed (OP_Program), a structure of this type
** is allocated to store the current value of the program counter, as
** well as the current memory cell array and various other frame specific
** values stored in the Vdbe struct. When the sub-program is finished,
** these values are copied back to the Vdbe from the VdbeFrame structure,

  i64 startTime;          /* Time when query started - used for profiling */
#endif
#ifdef SQLITE_DEBUG
  int rcApp;              /* errcode set by sqlite3_result_error_code() */
  u32 nWrite;             /* Number of write operations that have occurred */
#endif
  u16 nResColumn;         /* Number of columns in one row of the result set */
  u16 nResAlloc;          /* Column slots allocated to aColName[] */
  u8 errorAction;         /* Recovery action to do in case of an error */
  u8 minWriteFileFormat;  /* Minimum file format for writable database files */
  u8 prepFlags;           /* SQLITE_PREPARE_* flags */
  u8 eVdbeState;          /* On of the VDBE_*_STATE values */
  bft expired:2;          /* 1: recompile VM immediately  2: when convenient */
  bft explain:2;          /* 0: normal, 1: EXPLAIN, 2: EXPLAIN QUERY PLAN */
  bft changeCntOn:1;      /* True to update the change-counter */
  bft usesStmtJournal:1;  /* True if uses a statement journal */
  bft readOnly:1;         /* True for statements that do not write */
  bft bIsReader:1;        /* True for statements that read */
  bft haveEqpOps:1;       /* Bytecode supports EXPLAIN QUERY PLAN */
  yDbMask btreeMask;      /* Bitmask of db->aDb[] entries referenced */
  yDbMask lockMask;       /* Subset of btreeMask that requires a lock */
  u32 aCounter[9];        /* Counters used by sqlite3_stmt_status() */
  char *zSql;             /* Text of the SQL statement that generated this */
#ifdef SQLITE_ENABLE_NORMALIZE
  char *zNormSql;         /* Normalization of the associated SQL statement */
  DblquoteStr *pDblStr;   /* List of double-quoted string literals */

#else
SQLITE_PRIVATE int sqlite3VdbeMemSetZeroBlob(Mem*,int);
#endif
#ifdef SQLITE_DEBUG
SQLITE_PRIVATE int sqlite3VdbeMemIsRowSet(const Mem*);
#endif
SQLITE_PRIVATE int sqlite3VdbeMemSetRowSet(Mem*);
SQLITE_PRIVATE void sqlite3VdbeMemZeroTerminateIfAble(Mem*);
SQLITE_PRIVATE int sqlite3VdbeMemMakeWriteable(Mem*);
SQLITE_PRIVATE int sqlite3VdbeMemStringify(Mem*, u8, u8);
SQLITE_PRIVATE int sqlite3IntFloatCompare(i64,double);
SQLITE_PRIVATE i64 sqlite3VdbeIntValue(const Mem*);
SQLITE_PRIVATE int sqlite3VdbeMemIntegerify(Mem*);
SQLITE_PRIVATE double sqlite3VdbeRealValue(Mem*);
SQLITE_PRIVATE int sqlite3VdbeBooleanValue(Mem*, int ifNull);

SQLITE_API void sqlite3_str_appendf(StrAccum *p, const char *zFormat, ...){
  va_list ap;
  va_start(ap,zFormat);
  sqlite3_str_vappendf(p, zFormat, ap);
  va_end(ap);
}


/*****************************************************************************
** Reference counted string storage
*****************************************************************************/

/*
** Increase the reference count of the string by one.
**
** The input parameter is returned.
*/
SQLITE_PRIVATE char *sqlite3RCStrRef(char *z){
  RCStr *p = (RCStr*)z;
  assert( p!=0 );
  p--;
  p->nRCRef++;
  return z;
}

/*
** Decrease the reference count by one.  Free the string when the
** reference count reaches zero.
*/
SQLITE_PRIVATE void sqlite3RCStrUnref(char *z){
  RCStr *p = (RCStr*)z;
  assert( p!=0 );
  p--;
  assert( p->nRCRef>0 );
  if( p->nRCRef>=2 ){
    p->nRCRef--;
  }else{
    sqlite3_free(p);
  }
}

/*
** Create a new string that is capable of holding N bytes of text, not counting
** the zero byte at the end.  The string is uninitialized.
**
** The reference count is initially 1.  Call sqlite3RCStrUnref() to free the
** newly allocated string.
**
** This routine returns 0 on an OOM.
*/
SQLITE_PRIVATE char *sqlite3RCStrNew(u64 N){
  RCStr *p = sqlite3_malloc64( N + sizeof(*p) + 1 );
  if( p==0 ) return 0;
  p->nRCRef = 1;
  return (char*)&p[1];
}

/*
** Change the size of the string so that it is able to hold N bytes.
** The string might be reallocated, so return the new allocation.
*/
SQLITE_PRIVATE char *sqlite3RCStrResize(char *z, u64 N){
  RCStr *p = (RCStr*)z;
  RCStr *pNew;
  assert( p!=0 );
  p--;
  assert( p->nRCRef==1 );
  pNew = sqlite3_realloc64(p, N+sizeof(RCStr)+1);
  if( pNew==0 ){
    sqlite3_free(p);
    return 0;
  }else{
    return (char*)&pNew[1];
  }
}

/************** End of printf.c **********************************************/
/************** Begin file treeview.c ****************************************/
/*
** 2015-06-08
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:

      while( e>=10   ){ e-=10;  r *= 1.0e+10L;  }
      while( e>=1    ){ e-=1;   r *= 1.0e+01L;  }
    }else{
      while( e<=-100 ){ e+=100; r *= 1.0e-100L; }
      while( e<=-10  ){ e+=10;  r *= 1.0e-10L;  }
      while( e<=-1   ){ e+=1;   r *= 1.0e-01L;  }
    }
    assert( r>=0.0 );
    if( r>+1.7976931348623157081452742373e+308L ){
      *pResult = +INFINITY;
    }else{
      *pResult = (double)r;
    }
  }else{
    double rr[2];
    u64 s2;
    rr[0] = (double)s;
    s2 = (u64)rr[0];
    rr[1] = s>=s2 ? (double)(s - s2) : -(double)(s2 - s);
    if( e>0 ){

    memcpy(pOut, &u, 8);
    if( k-i>16 ) return 2;
    if( z[k]!=0 ) return 1;
    return 0;
  }else
#endif /* SQLITE_OMIT_HEX_INTEGER */
  {
    int n = (int)(0x3fffffff&strspn(z,"+- \n\t0123456789"));
    if( z[n] ) n++;
    return sqlite3Atoi64(z, pOut, n, SQLITE_UTF8);
  }
}

/*
** If zNum represents an integer that will fit in 32-bits, then set
** *pValue to that integer and return true.  Otherwise return false.
**

  iLast = pWal->hdr.mxFrame;

  /* Allocate space for the WalIterator object. */
  nSegment = walFramePage(iLast) + 1;
  nByte = sizeof(WalIterator)
        + (nSegment-1)*sizeof(struct WalSegment)
        + iLast*sizeof(ht_slot);
  p = (WalIterator *)sqlite3_malloc64(nByte
      + sizeof(ht_slot) * (iLast>HASHTABLE_NPAGE?HASHTABLE_NPAGE:iLast)
  );
  if( !p ){
    return SQLITE_NOMEM_BKPT;
  }
  memset(p, 0, nByte);
  p->nSegment = nSegment;




  aTmp = (ht_slot*)&(((u8*)p)[nByte]);






  for(i=walFramePage(nBackfill+1); rc==SQLITE_OK && i<nSegment; i++){
    WalHashLoc sLoc;

    rc = walHashGet(pWal, i, &sLoc);
    if( rc==SQLITE_OK ){
      int j;                      /* Counter variable */
      int nEntry;                 /* Number of entries in this segment */

      walMergesort((u32 *)sLoc.aPgno, aTmp, aIndex, &nEntry);
      p->aSegment[i].iZero = sLoc.iZero;
      p->aSegment[i].nEntry = nEntry;
      p->aSegment[i].aIndex = aIndex;
      p->aSegment[i].aPgno = (u32 *)sLoc.aPgno;
    }
  }


  if( rc!=SQLITE_OK ){
    walIteratorFree(p);
    p = 0;
  }
  *pp = p;
  return rc;
}

** allows a 64-bit integer to be encoded in 9 bytes.
**
**    0x00                      becomes  0x00000000
**    0x7f                      becomes  0x0000007f
**    0x81 0x00                 becomes  0x00000080
**    0x82 0x00                 becomes  0x00000100
**    0x80 0x7f                 becomes  0x0000007f
**    0x81 0x91 0xd1 0xac 0x78  becomes  0x12345678
**    0x81 0x81 0x81 0x81 0x01  becomes  0x10204081
**
** Variable length integers are used for rowids and to hold the number of
** bytes of key and data in a btree cell.
**
** The content of a cell looks like this:
**

static void ptrmapPutOvflPtr(MemPage *pPage, MemPage *pSrc, u8 *pCell,int *pRC){
  CellInfo info;
  if( *pRC ) return;
  assert( pCell!=0 );
  pPage->xParseCell(pPage, pCell, &info);
  if( info.nLocal<info.nPayload ){
    Pgno ovfl;
    if( SQLITE_OVERFLOW(pSrc->aDataEnd, pCell, pCell+info.nLocal) ){
      testcase( pSrc!=pPage );
      *pRC = SQLITE_CORRUPT_BKPT;
      return;
    }
    ovfl = get4byte(&pCell[info.nSize-4]);
    ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno, pRC);
  }

  pCur->curFlags |= BTCF_Pinned;
}
SQLITE_PRIVATE void sqlite3BtreeCursorUnpin(BtCursor *pCur){
  assert( (pCur->curFlags & BTCF_Pinned)!=0 );
  pCur->curFlags &= ~BTCF_Pinned;
}


/*
** Return the offset into the database file for the start of the
** payload to which the cursor is pointing.
*/
SQLITE_PRIVATE i64 sqlite3BtreeOffset(BtCursor *pCur){
  assert( cursorHoldsMutex(pCur) );
  assert( pCur->eState==CURSOR_VALID );
  getCellInfo(pCur);
  return (i64)pCur->pBt->pageSize*((i64)pCur->pPage->pgno - 1) +
         (i64)(pCur->info.pPayload - pCur->pPage->aData);
}


/*
** Return the number of bytes of payload for the entry that pCur is
** currently pointing to.  For table btrees, this will be the amount
** of data.  For index btrees, this will be the size of the key.
**
** The caller must guarantee that the cursor is pointing to a non-NULL

      }
    }
    iOvflSpace += sz;
    assert( sz<=pBt->maxLocal+23 );
    assert( iOvflSpace <= (int)pBt->pageSize );
    for(k=0; ALWAYS(k<NB*2) && b.ixNx[k]<=j; k++){}
    pSrcEnd = b.apEnd[k];
    if( SQLITE_OVERFLOW(pSrcEnd, pCell, pCell+sz) ){
      rc = SQLITE_CORRUPT_BKPT;
      goto balance_cleanup;
    }
    rc = insertCell(pParent, nxDiv+i, pCell, sz, pTemp, pNew->pgno);
    if( rc!=SQLITE_OK ) goto balance_cleanup;
    assert( sqlite3PagerIswriteable(pParent->pDbPage) );
  }

    return sqlite3VdbeMemGrow(pMem, szNew, 0);
  }
  assert( (pMem->flags & MEM_Dyn)==0 );
  pMem->z = pMem->zMalloc;
  pMem->flags &= (MEM_Null|MEM_Int|MEM_Real|MEM_IntReal);
  return SQLITE_OK;
}

/*
** If pMem is already a string, detect if it is a zero-terminated
** string, or make it into one if possible, and mark it as such.
**
** This is an optimization.  Correct operation continues even if
** this routine is a no-op.
*/
SQLITE_PRIVATE void sqlite3VdbeMemZeroTerminateIfAble(Mem *pMem){
  if( (pMem->flags & (MEM_Str|MEM_Term|MEM_Ephem|MEM_Static))!=MEM_Str ){
    /* pMem must be a string, and it cannot be an ephemeral or static string */
    return;
  }
  if( pMem->enc!=SQLITE_UTF8 ) return;
  if( NEVER(pMem->z==0) ) return;
  if( pMem->flags & MEM_Dyn ){
    if( pMem->xDel==sqlite3_free
     && sqlite3_msize(pMem->z) >= (u64)(pMem->n+1)
    ){
      pMem->z[pMem->n] = 0;
      pMem->flags |= MEM_Term;
      return;
    }
    if( pMem->xDel==(void(*)(void*))sqlite3RCStrUnref ){
      /* Blindly assume that all RCStr objects are zero-terminated */
      pMem->flags |= MEM_Term;
      return;
    }
  }else if( pMem->szMalloc >= pMem->n+1 ){
    pMem->z[pMem->n] = 0;
    pMem->flags |= MEM_Term;
    return;
  }
}

/*
** It is already known that pMem contains an unterminated string.
** Add the zero terminator.
**
** Three bytes of zero are added.  In this way, there is guaranteed
** to be a double-zero byte at an even byte boundary in order to

      break;
    }
    case SQLITE_AFF_REAL: {
      sqlite3VdbeMemRealify(pMem);
      break;
    }
    default: {
      int rc;
      assert( aff==SQLITE_AFF_TEXT );
      assert( MEM_Str==(MEM_Blob>>3) );
      pMem->flags |= (pMem->flags&MEM_Blob)>>3;
      sqlite3ValueApplyAffinity(pMem, SQLITE_AFF_TEXT, encoding);
      assert( pMem->flags & MEM_Str || pMem->db->mallocFailed );
      pMem->flags &= ~(MEM_Int|MEM_Real|MEM_IntReal|MEM_Blob|MEM_Zero);
      if( encoding!=SQLITE_UTF8 ) pMem->n &= ~1;
      rc = sqlite3VdbeChangeEncoding(pMem, encoding);
      if( rc ) return rc;
      sqlite3VdbeMemZeroTerminateIfAble(pMem);
    }
  }
  return SQLITE_OK;
}

/*
** Initialize bulk memory to be a consistent Mem object.

    return pVal->z;
  }
  if( pVal->flags&MEM_Null ){
    return 0;
  }
  return valueToText(pVal, enc);
}

/* Return true if sqlit3_value object pVal is a string or blob value
** that uses the destructor specified in the second argument.
**
** TODO:  Maybe someday promote this interface into a published API so
** that third-party extensions can get access to it?
*/
SQLITE_PRIVATE int sqlite3ValueIsOfClass(const sqlite3_value *pVal, void(*xFree)(void*)){
  if( ALWAYS(pVal!=0)
   && ALWAYS((pVal->flags & (MEM_Str|MEM_Blob))!=0)
   && (pVal->flags & MEM_Dyn)!=0
   && pVal->xDel==xFree
  ){
    return 1;
  }else{
    return 0;
  }
}

/*
** Create a new sqlite3_value object.
*/
SQLITE_PRIVATE sqlite3_value *sqlite3ValueNew(sqlite3 *db){
  Mem *p = sqlite3DbMallocZero(db, sizeof(*p));
  if( p ){

  if( N>0 ){
    sqlite3VdbeAddOp3(pParse->pVdbe, OP_ReleaseReg, iFirst, N, *(int*)&mask);
    if( bUndefine ) sqlite3VdbeChangeP5(pParse->pVdbe, 1);
  }
}
#endif /* SQLITE_DEBUG */


/*
** Change the value of the P4 operand for a specific instruction.
** This routine is useful when a large program is loaded from a
** static array using sqlite3VdbeAddOpList but we want to make a
** few minor changes to the program.
**
** If n>=0 then the P4 operand is dynamic, meaning that a copy of

    }else{
      char *zP4 = sqlite3VdbeDisplayP4(db, pOp);
      if( p->explain==2 ){
        sqlite3VdbeMemSetInt64(pMem, pOp->p1);
        sqlite3VdbeMemSetInt64(pMem+1, pOp->p2);
        sqlite3VdbeMemSetInt64(pMem+2, pOp->p3);
        sqlite3VdbeMemSetStr(pMem+3, zP4, -1, SQLITE_UTF8, sqlite3_free);
        assert( p->nResColumn==4 );
      }else{
        sqlite3VdbeMemSetInt64(pMem+0, i);
        sqlite3VdbeMemSetStr(pMem+1, (char*)sqlite3OpcodeName(pOp->opcode),
                             -1, SQLITE_UTF8, SQLITE_STATIC);
        sqlite3VdbeMemSetInt64(pMem+2, pOp->p1);
        sqlite3VdbeMemSetInt64(pMem+3, pOp->p2);
        sqlite3VdbeMemSetInt64(pMem+4, pOp->p3);
        /* pMem+5 for p4 is done last */
        sqlite3VdbeMemSetInt64(pMem+6, pOp->p5);
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
        {
          char *zCom = sqlite3VdbeDisplayComment(db, pOp, zP4);
          sqlite3VdbeMemSetStr(pMem+7, zCom, -1, SQLITE_UTF8, sqlite3_free);
        }
#else
        sqlite3VdbeMemSetNull(pMem+7);
#endif
        sqlite3VdbeMemSetStr(pMem+5, zP4, -1, SQLITE_UTF8, sqlite3_free);
        assert( p->nResColumn==8 );
      }
      p->pResultRow = pMem;
      if( db->mallocFailed ){
        p->rc = SQLITE_NOMEM;
        rc = SQLITE_ERROR;
      }else{
        p->rc = SQLITE_OK;

  x.nFree = ROUNDDOWN8(pParse->szOpAlloc - n);  /* Bytes of unused memory */
  assert( x.nFree>=0 );
  assert( EIGHT_BYTE_ALIGNMENT(&x.pSpace[x.nFree]) );

  resolveP2Values(p, &nArg);
  p->usesStmtJournal = (u8)(pParse->isMultiWrite && pParse->mayAbort);
  if( pParse->explain ){





    if( nMem<10 ) nMem = 10;
    p->explain = pParse->explain;



    p->nResColumn = 12 - 4*p->explain;









  }
  p->expired = 0;

  /* Memory for registers, parameters, cursor, etc, is allocated in one or two
  ** passes.  On the first pass, we try to reuse unused memory at the
  ** end of the opcode array.  If we are unable to satisfy all memory
  ** requirements by reusing the opcode array tail, then the second

/*
** Close a VDBE cursor and release all the resources that cursor
** happens to hold.
*/
SQLITE_PRIVATE void sqlite3VdbeFreeCursor(Vdbe *p, VdbeCursor *pCx){
  if( pCx ) sqlite3VdbeFreeCursorNN(p,pCx);
}
static SQLITE_NOINLINE void freeCursorWithCache(Vdbe *p, VdbeCursor *pCx){
  VdbeTxtBlbCache *pCache = pCx->pCache;
  assert( pCx->colCache );
  pCx->colCache = 0;
  pCx->pCache = 0;
  if( pCache->pCValue ){
    sqlite3RCStrUnref(pCache->pCValue);
    pCache->pCValue = 0;
  }
  sqlite3DbFree(p->db, pCache);
  sqlite3VdbeFreeCursorNN(p, pCx);
}
SQLITE_PRIVATE void sqlite3VdbeFreeCursorNN(Vdbe *p, VdbeCursor *pCx){
  if( pCx->colCache ){
    freeCursorWithCache(p, pCx);
    return;
  }
  switch( pCx->eCurType ){
    case CURTYPE_SORTER: {
      sqlite3VdbeSorterClose(p->db, pCx);
      break;
    }
    case CURTYPE_BTREE: {
      assert( pCx->uc.pCursor!=0 );

** execution of the vdbe program so that sqlite3_column_count() can
** be called on an SQL statement before sqlite3_step().
*/
SQLITE_PRIVATE void sqlite3VdbeSetNumCols(Vdbe *p, int nResColumn){
  int n;
  sqlite3 *db = p->db;

  if( p->nResAlloc ){
    releaseMemArray(p->aColName, p->nResAlloc*COLNAME_N);
    sqlite3DbFree(db, p->aColName);
  }
  n = nResColumn*COLNAME_N;
  p->nResColumn = p->nResAlloc = (u16)nResColumn;
  p->aColName = (Mem*)sqlite3DbMallocRawNN(db, sizeof(Mem)*n );
  if( p->aColName==0 ) return;
  initMemArray(p->aColName, n, db, MEM_Null);
}

/*
** Set the name of the idx'th column to be returned by the SQL statement.

  int idx,                         /* Index of column zName applies to */
  int var,                         /* One of the COLNAME_* constants */
  const char *zName,               /* Pointer to buffer containing name */
  void (*xDel)(void*)              /* Memory management strategy for zName */
){
  int rc;
  Mem *pColName;
  assert( idx<p->nResAlloc );
  assert( var<COLNAME_N );
  if( p->db->mallocFailed ){
    assert( !zName || xDel!=SQLITE_DYNAMIC );
    return SQLITE_NOMEM_BKPT;
  }
  assert( p->aColName!=0 );
  pColName = &(p->aColName[idx+var*p->nResAlloc]);
  rc = sqlite3VdbeMemSetStr(pColName, zName, -1, SQLITE_UTF8, xDel);
  assert( rc!=0 || !zName || (pColName->flags&MEM_Term)!=0 );
  return rc;
}

/*
** A read or write transaction may or may not be active on database handle

** the database connection and frees the object itself.
*/
static void sqlite3VdbeClearObject(sqlite3 *db, Vdbe *p){
  SubProgram *pSub, *pNext;
  assert( db!=0 );
  assert( p->db==0 || p->db==db );
  if( p->aColName ){
    releaseMemArray(p->aColName, p->nResAlloc*COLNAME_N);
    sqlite3DbNNFreeNN(db, p->aColName);
  }
  for(pSub=p->pProgram; pSub; pSub=pNext){
    pNext = pSub->pNext;
    vdbeFreeOpArray(db, pSub->aOp, pSub->nOp);
    sqlite3DbFree(db, pSub);
  }

    if( enc==SQLITE_UTF16 ) enc = SQLITE_UTF16NATIVE;
    n &= ~(u64)1;
  }
  if( n>0x7fffffff ){
    (void)invokeValueDestructor(z, xDel, pCtx);
  }else{
    setResultStrOrError(pCtx, z, (int)n, enc, xDel);
    sqlite3VdbeMemZeroTerminateIfAble(pCtx->pOut);
  }
}
#ifndef SQLITE_OMIT_UTF16
SQLITE_API void sqlite3_result_text16(
  sqlite3_context *pCtx,
  const void *z,
  int n,

#endif

/*
** Return the number of columns in the result set for the statement pStmt.
*/
SQLITE_API int sqlite3_column_count(sqlite3_stmt *pStmt){
  Vdbe *pVm = (Vdbe *)pStmt;
  if( pVm==0 ) return 0;
  return pVm->nResColumn;
}

/*
** Return the number of values available from the current row of the
** currently executing statement pStmt.
*/
SQLITE_API int sqlite3_data_count(sqlite3_stmt *pStmt){

#endif /* SQLITE_OMIT_UTF16 */
SQLITE_API int sqlite3_column_type(sqlite3_stmt *pStmt, int i){
  int iType = sqlite3_value_type( columnMem(pStmt,i) );
  columnMallocFailure(pStmt);
  return iType;
}

/*
** Column names appropriate for EXPLAIN or EXPLAIN QUERY PLAN.
*/
static const char * const azExplainColNames8[] = {
   "addr", "opcode", "p1", "p2", "p3", "p4", "p5", "comment",  /* EXPLAIN */
   "id", "parent", "notused", "detail"                         /* EQP */
};
static const u16 azExplainColNames16data[] = {
  /*   0 */  'a', 'd', 'd', 'r',                0,
  /*   5 */  'o', 'p', 'c', 'o', 'd', 'e',      0,
  /*  12 */  'p', '1',                          0,
  /*  15 */  'p', '2',                          0,
  /*  18 */  'p', '3',                          0,
  /*  21 */  'p', '4',                          0,
  /*  24 */  'p', '5',                          0,
  /*  27 */  'c', 'o', 'm', 'm', 'e', 'n', 't', 0,
  /*  35 */  'i', 'd',                          0,
  /*  38 */  'p', 'a', 'r', 'e', 'n', 't',      0,
  /*  45 */  'n', 'o', 't', 'u', 's', 'e', 'd', 0,
  /*  53 */  'd', 'e', 't', 'a', 'i', 'l',      0
};
static const u8 iExplainColNames16[] = {
  0, 5, 12, 15, 18, 21, 24, 27,
  35, 38, 45, 53
};

/*
** Convert the N-th element of pStmt->pColName[] into a string using
** xFunc() then return that string.  If N is out of range, return 0.
**
** There are up to 5 names for each column.  useType determines which
** name is returned.  Here are the names:
**

  sqlite3 *db;
#ifdef SQLITE_ENABLE_API_ARMOR
  if( pStmt==0 ){
    (void)SQLITE_MISUSE_BKPT;
    return 0;
  }
#endif
  if( N<0 ) return 0;
  ret = 0;
  p = (Vdbe *)pStmt;
  db = p->db;
  assert( db!=0 );
  sqlite3_mutex_enter(db->mutex);

  if( p->explain ){
    if( useType>0 ) goto columnName_end;
    n = p->explain==1 ? 8 : 4;
    if( N>=n ) goto columnName_end;
    if( useUtf16 ){
      int i = iExplainColNames16[N + 8*p->explain - 8];
      ret = (void*)&azExplainColNames16data[i];
    }else{
      ret = (void*)azExplainColNames8[N + 8*p->explain - 8];
    }
    goto columnName_end;
  }
  n = p->nResColumn;
  if( N<n ){
    u8 prior_mallocFailed = db->mallocFailed;
    N += useType*n;

#ifndef SQLITE_OMIT_UTF16
    if( useUtf16 ){
      ret = sqlite3_value_text16((sqlite3_value*)&p->aColName[N]);
    }else
#endif
    {
      ret = sqlite3_value_text((sqlite3_value*)&p->aColName[N]);
    }
    /* A malloc may have failed inside of the _text() call. If this
    ** is the case, clear the mallocFailed flag and return NULL.
    */
    assert( db->mallocFailed==0 || db->mallocFailed==1 );
    if( db->mallocFailed > prior_mallocFailed ){
      sqlite3OomClear(db);
      ret = 0;
    }

  }
columnName_end:
  sqlite3_mutex_leave(db->mutex);
  return ret;
}

/*
** Return the name of the Nth column of the result set returned by SQL
** statement pStmt.
*/

/*
** Return 1 if the statement is an EXPLAIN and return 2 if the
** statement is an EXPLAIN QUERY PLAN
*/
SQLITE_API int sqlite3_stmt_isexplain(sqlite3_stmt *pStmt){
  return pStmt ? ((Vdbe*)pStmt)->explain : 0;
}

/*
** Set the explain mode for a statement.
*/
SQLITE_API int sqlite3_stmt_explain(sqlite3_stmt *pStmt, int eMode){
  Vdbe *v = (Vdbe*)pStmt;
  int rc;
  sqlite3_mutex_enter(v->db->mutex);
  if( v->explain==eMode ){
    rc = SQLITE_OK;
  }else if( eMode<0 || eMode>2 ){
    rc = SQLITE_ERROR;
  }else if( (v->prepFlags & SQLITE_PREPARE_SAVESQL)==0 ){
    rc = SQLITE_ERROR;
  }else if( v->eVdbeState!=VDBE_READY_STATE ){
    rc = SQLITE_BUSY;
  }else if( v->nMem>=10 && (eMode!=2 || v->haveEqpOps) ){
    /* No reprepare necessary */
    v->explain = eMode;
    rc = SQLITE_OK;
  }else{
    v->explain = eMode;
    rc = sqlite3Reprepare(v);
    v->haveEqpOps = eMode==2;
  }
  if( v->explain ){
    v->nResColumn = 12 - 4*v->explain;
  }else{
    v->nResColumn = v->nResAlloc;
  }
  sqlite3_mutex_leave(v->db->mutex);
  return rc;
}

/*
** Return true if the prepared statement is in need of being reset.
*/
SQLITE_API int sqlite3_stmt_busy(sqlite3_stmt *pStmt){
  Vdbe *v = (Vdbe*)pStmt;
  return v!=0 && v->eVdbeState==VDBE_RUN_STATE;

    }
    sqlite3_str_appendf(pStr, " %c%d[", c, pMem->n);
    for(j=0; j<25 && j<pMem->n; j++){
      c = pMem->z[j];
      sqlite3_str_appendchar(pStr, 1, (c>=0x20&&c<=0x7f) ? c : '.');
    }
    sqlite3_str_appendf(pStr, "]%s", encnames[pMem->enc]);
    if( f & MEM_Term ){
      sqlite3_str_appendf(pStr, "(0-term)");
    }
  }
}
#endif

#ifdef SQLITE_DEBUG
/*
** Print the value of a register for tracing purposes:

      ** though, at least, those hashes are different from each other and
      ** from NULL. */
      h += 4093 + (p->flags & (MEM_Str|MEM_Blob));
    }
  }
  return h;
}


/*
** For OP_Column, factor out the case where content is loaded from
** overflow pages, so that the code to implement this case is separate
** the common case where all content fits on the page.  Factoring out
** the code reduces register pressure and helps the common case
** to run faster.
*/
static SQLITE_NOINLINE int vdbeColumnFromOverflow(
  VdbeCursor *pC,       /* The BTree cursor from which we are reading */
  int iCol,             /* The column to read */
  int t,                /* The serial-type code for the column value */
  i64 iOffset,          /* Offset to the start of the content value */
  u32 cacheStatus,      /* Current Vdbe.cacheCtr value */
  u32 colCacheCtr,      /* Current value of the column cache counter */
  Mem *pDest            /* Store the value into this register. */
){
  int rc;
  sqlite3 *db = pDest->db;
  int encoding = pDest->enc;
  int len = sqlite3VdbeSerialTypeLen(t);
  assert( pC->eCurType==CURTYPE_BTREE );
  if( len>db->aLimit[SQLITE_LIMIT_LENGTH] ) return SQLITE_TOOBIG;
  if( len > 4000 && pC->pKeyInfo==0 ){
    /* Cache large column values that are on overflow pages using
    ** an RCStr (reference counted string) so that if they are reloaded,
    ** that do not have to be copied a second time.  The overhead of
    ** creating and managing the cache is such that this is only
    ** profitable for larger TEXT and BLOB values.
    **
    ** Only do this on table-btrees so that writes to index-btrees do not
    ** need to clear the cache.  This buys performance in the common case
    ** in exchange for generality.
    */
    VdbeTxtBlbCache *pCache;
    char *pBuf;
    if( pC->colCache==0 ){
      pC->pCache = sqlite3DbMallocZero(db, sizeof(VdbeTxtBlbCache) );
      if( pC->pCache==0 ) return SQLITE_NOMEM;
      pC->colCache = 1;
    }
    pCache = pC->pCache;
    if( pCache->pCValue==0
     || pCache->iCol!=iCol
     || pCache->cacheStatus!=cacheStatus
     || pCache->colCacheCtr!=colCacheCtr
     || pCache->iOffset!=sqlite3BtreeOffset(pC->uc.pCursor)
    ){
      if( pCache->pCValue ) sqlite3RCStrUnref(pCache->pCValue);
      pBuf = pCache->pCValue = sqlite3RCStrNew( len+3 );
      if( pBuf==0 ) return SQLITE_NOMEM;
      rc = sqlite3BtreePayload(pC->uc.pCursor, iOffset, len, pBuf);
      if( rc ) return rc;
      pBuf[len] = 0;
      pBuf[len+1] = 0;
      pBuf[len+2] = 0;
      pCache->iCol = iCol;
      pCache->cacheStatus = cacheStatus;
      pCache->colCacheCtr = colCacheCtr;
      pCache->iOffset = sqlite3BtreeOffset(pC->uc.pCursor);
    }else{
      pBuf = pCache->pCValue;
    }
    assert( t>=12 );
    sqlite3RCStrRef(pBuf);
    if( t&1 ){
      rc = sqlite3VdbeMemSetStr(pDest, pBuf, len, encoding,
                                (void(*)(void*))sqlite3RCStrUnref);
      pDest->flags |= MEM_Term;
    }else{
      rc = sqlite3VdbeMemSetStr(pDest, pBuf, len, 0,
                                (void(*)(void*))sqlite3RCStrUnref);
    }
  }else{
    rc = sqlite3VdbeMemFromBtree(pC->uc.pCursor, iOffset, len, pDest);
    if( rc ) return rc;
    sqlite3VdbeSerialGet((const u8*)pDest->z, t, pDest);
    if( (t&1)!=0 && encoding==SQLITE_UTF8 ){
      pDest->z[len] = 0;
      pDest->flags |= MEM_Term;
    }
  }
  pDest->flags &= ~MEM_Ephem;
  return rc;
}


/*
** Return the symbolic name for the data type of a pMem
*/
static const char *vdbeMemTypeName(Mem *pMem){
  static const char *azTypes[] = {
      /* SQLITE_INTEGER */ "INT",

  u64 nProgressLimit;        /* Invoke xProgress() when nVmStep reaches this */
#endif
  Mem *aMem = p->aMem;       /* Copy of p->aMem */
  Mem *pIn1 = 0;             /* 1st input operand */
  Mem *pIn2 = 0;             /* 2nd input operand */
  Mem *pIn3 = 0;             /* 3rd input operand */
  Mem *pOut = 0;             /* Output operand */
  u32 colCacheCtr = 0;       /* Column cache counter */
#if defined(SQLITE_ENABLE_STMT_SCANSTATUS) || defined(VDBE_PROFILE)
  u64 *pnCycle = 0;
  int bStmtScanStatus = IS_STMT_SCANSTATUS(db)!=0;
#endif
  /*** INSERT STACK UNION HERE ***/

  assert( p->eVdbeState==VDBE_RUN_STATE );  /* sqlite3_step() verifies this */

      pDest->z[len] = 0;
      pDest->z[len+1] = 0;
      pDest->flags = aFlag[t&1];
    }
  }else{
    u8 p5;
    pDest->enc = encoding;
    assert( pDest->db==db );
    /* This branch happens only when content is on overflow pages */
    if( ((p5 = (pOp->p5 & OPFLAG_BYTELENARG))!=0
          && (p5==OPFLAG_TYPEOFARG
              || (t>=12 && ((t&1)==0 || p5==OPFLAG_BYTELENARG))
             )
        )
     || (len = sqlite3VdbeSerialTypeLen(t))==0

      ** buffer passed to it, debugging function VdbeMemPrettyPrint() may
      ** read more.  Use the global constant sqlite3CtypeMap[] as the array,
      ** as that array is 256 bytes long (plenty for VdbeMemPrettyPrint())
      ** and it begins with a bunch of zeros.
      */
      sqlite3VdbeSerialGet((u8*)sqlite3CtypeMap, t, pDest);
    }else{
      rc = vdbeColumnFromOverflow(pC, p2, t, aOffset[p2],
                p->cacheCtr, colCacheCtr, pDest);
      if( rc ){
        if( rc==SQLITE_NOMEM ) goto no_mem;
        if( rc==SQLITE_TOOBIG ) goto too_big;

        goto abort_due_to_error;


      }
    }
  }

op_column_out:
  UPDATE_MAX_BLOBSIZE(pDest);
  REGISTER_TRACE(pOp->p3, pDest);
  break;

  assert( BTREE_PREFORMAT==OPFLAG_PREFORMAT );
  rc = sqlite3BtreeInsert(pC->uc.pCursor, &x,
      (pOp->p5 & (OPFLAG_APPEND|OPFLAG_SAVEPOSITION|OPFLAG_PREFORMAT)),
      seekResult
  );
  pC->deferredMoveto = 0;
  pC->cacheStatus = CACHE_STALE;
  colCacheCtr++;

  /* Invoke the update-hook if required. */
  if( rc ) goto abort_due_to_error;
  if( pTab ){
    assert( db->xUpdateCallback!=0 );
    assert( pTab->aCol!=0 );
    db->xUpdateCallback(db->pUpdateArg,

      nExtraDelete--;
    }
  }
#endif

  rc = sqlite3BtreeDelete(pC->uc.pCursor, pOp->p5);
  pC->cacheStatus = CACHE_STALE;
  colCacheCtr++;
  pC->seekResult = 0;
  if( rc ) goto abort_due_to_error;

  /* Invoke the update-hook if required. */
  if( opflags & OPFLAG_NCHANGE ){
    p->nChange++;
    if( db->xUpdateCallback && ALWAYS(pTab!=0) && HasRowid(pTab) ){

      "p1 INT,"
      "p2 INT,"
      "p3 INT,"
      "p4 TEXT,"
      "p5 INT,"
      "comment TEXT,"
      "subprog TEXT,"
      "nexec INT,"
      "ncycle INT,"
      "stmt HIDDEN"
    ");",

    /* Tables_used() schema */
    "CREATE TABLE x("
      "type TEXT,"
      "schema TEXT,"

            if( pIdx->tnum==iRoot ){
              pCur->zName = pIdx->zName;
              pCur->zType = "index";
            }
          }
        }
      }
      i += 20;
    }
  }
  switch( i ){
    case 0:   /* addr */
      sqlite3_result_int(ctx, pCur->iAddr);
      break;
    case 1:   /* opcode */

      }else if( aOp[0].p4.z!=0 ){
         sqlite3_result_text(ctx, aOp[0].p4.z+3, -1, SQLITE_STATIC);
      }else{
         sqlite3_result_text(ctx, "(FK)", 4, SQLITE_STATIC);
      }
      break;
    }

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
    case 9:     /* nexec */
      sqlite3_result_int(ctx, pOp->nExec);
      break;
    case 10:    /* ncycle */
      sqlite3_result_int(ctx, pOp->nCycle);
      break;
#else
    case 9:     /* nexec */
    case 10:    /* ncycle */
      sqlite3_result_int(ctx, 0);
      break;
#endif

    case 20:  /* tables_used.type */
      sqlite3_result_text(ctx, pCur->zType, -1, SQLITE_STATIC);
      break;
    case 21:  /* tables_used.schema */
      sqlite3_result_text(ctx, pCur->zSchema, -1, SQLITE_STATIC);
      break;
    case 22:  /* tables_used.name */
      sqlite3_result_text(ctx, pCur->zName, -1, SQLITE_STATIC);
      break;
    case 23:  /* tables_used.wr */
      sqlite3_result_int(ctx, pOp->opcode==OP_OpenWrite);
      break;
  }
  return SQLITE_OK;
}

/*

  sqlite3_vtab *tab,
  sqlite3_index_info *pIdxInfo
){
  int i;
  int rc = SQLITE_CONSTRAINT;
  struct sqlite3_index_constraint *p;
  bytecodevtab *pVTab = (bytecodevtab*)tab;
  int iBaseCol = pVTab->bTablesUsed ? 4 : 10;
  pIdxInfo->estimatedCost = (double)100;
  pIdxInfo->estimatedRows = 100;
  pIdxInfo->idxNum = 0;
  for(i=0, p=pIdxInfo->aConstraint; i<pIdxInfo->nConstraint; i++, p++){
    if( p->usable==0 ) continue;
    if( p->op==SQLITE_INDEX_CONSTRAINT_EQ && p->iColumn==iBaseCol+1 ){
      rc = SQLITE_OK;

            testcase( (pDef->funcFlags & OPFLAG_BYTELENARG)==OPFLAG_LENGTHARG );
            testcase( (pDef->funcFlags & OPFLAG_BYTELENARG)==OPFLAG_TYPEOFARG );
            testcase( (pDef->funcFlags & OPFLAG_BYTELENARG)==OPFLAG_BYTELENARG);
            pFarg->a[0].pExpr->op2 = pDef->funcFlags & OPFLAG_BYTELENARG;
          }
        }

        sqlite3ExprCodeExprList(pParse, pFarg, r1, 0, SQLITE_ECEL_FACTOR);

      }else{
        r1 = 0;
      }
#ifndef SQLITE_OMIT_VIRTUALTABLE
      /* Possibly overload the function if the first argument is
      ** a virtual table column.
      **

    **  ONEPASS_SINGLE: One-pass approach - at most one row deleted.
    **  ONEPASS_MULTI:  One-pass approach - any number of rows may be deleted.
    */
    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0, 0,0,wcf,iTabCur+1);
    if( pWInfo==0 ) goto delete_from_cleanup;
    eOnePass = sqlite3WhereOkOnePass(pWInfo, aiCurOnePass);
    assert( IsVirtual(pTab)==0 || eOnePass!=ONEPASS_MULTI );
    assert( IsVirtual(pTab) || bComplex || eOnePass!=ONEPASS_OFF
            || OptimizationDisabled(db, SQLITE_OnePass) );
    if( eOnePass!=ONEPASS_SINGLE ) sqlite3MultiWrite(pParse);
    if( sqlite3WhereUsesDeferredSeek(pWInfo) ){
      sqlite3VdbeAddOp1(v, OP_FinishSeek, iTabCur);
    }

    /* Keep track of the number of rows to be deleted */
    if( memCnt ){

    }else{
      *zOut++ = 0xF0 + (u8)((c>>18) & 0x07);
      *zOut++ = 0x80 + (u8)((c>>12) & 0x3F);
      *zOut++ = 0x80 + (u8)((c>>6) & 0x3F);
      *zOut++ = 0x80 + (u8)(c & 0x3F);
    }                                                    \
  }
  *zOut = 0;
  sqlite3_result_text64(context, (char*)z, zOut-z, sqlite3_free, SQLITE_UTF8);
}

/*
** The hex() function.  Interpret the argument as a blob.  Return
** a hexadecimal rendering as text.
*/

        i64 x = p->iSum;
        if( sqlite3AddInt64(&x, sqlite3_value_int64(argv[0]))==0 ){
          p->iSum = x;
        }else{
          p->ovrfl = 1;
          kahanBabuskaNeumaierInit(p, p->iSum);
          p->approx = 1;
          kahanBabuskaNeumaierStepInt64(p, sqlite3_value_int64(argv[0]));
        }
      }
    }else{

      if( type==SQLITE_INTEGER ){
        kahanBabuskaNeumaierStepInt64(p, sqlite3_value_int64(argv[0]));
      }else{
        p->ovrfl = 0;
        kahanBabuskaNeumaierStep(p, sqlite3_value_double(argv[0]));
      }
    }

  /* sqlite3ParseObjectInit(&sParse, db); // inlined for performance */
  memset(PARSE_HDR(&sParse), 0, PARSE_HDR_SZ);
  memset(PARSE_TAIL(&sParse), 0, PARSE_TAIL_SZ);
  sParse.pOuterParse = db->pParse;
  db->pParse = &sParse;
  sParse.db = db;
  if( pReprepare ){
    sParse.pReprepare = pReprepare;
    sParse.explain = sqlite3_stmt_isexplain((sqlite3_stmt*)pReprepare);
  }else{
    assert( sParse.pReprepare==0 );
  }
  assert( ppStmt && *ppStmt==0 );
  if( db->mallocFailed ){
    sqlite3ErrorMsg(&sParse, "out of memory");
    db->errCode = rc = SQLITE_NOMEM;
    goto end_prepare;
  }
  assert( sqlite3_mutex_held(db->mutex) );

  Table *pTab;
  SrcList *pTabList;
  ExprList *pEList;
  sqlite3 *db = pParse->db;
  int fullName;    /* TABLE.COLUMN if no AS clause and is a direct table ref */
  int srcName;     /* COLUMN or TABLE.COLUMN if no AS clause and is direct */








  if( pParse->colNamesSet ) return;
  /* Column names are determined by the left-most term of a compound select */
  while( pSelect->pPrior ) pSelect = pSelect->pPrior;
  TREETRACE(0x80,pParse,pSelect,("generating column names\n"));
  pTabList = pSelect->pSrc;
  pEList = pSelect->pEList;
  assert( v!=0 );

**
**  (27)  The subquery may not contain a FULL or RIGHT JOIN unless it
**        is the first element of the parent query.  Two subcases:
**        (27a) the subquery is not a compound query.
**        (27b) the subquery is a compound query and the RIGHT JOIN occurs
**              in any arm of the compound query.  (See also (17g).)
**
**  (28)  The subquery is not a MATERIALIZED CTE.  (This is handled
**        in the caller before ever reaching this routine.)
**
**
** In this routine, the "p" parameter is a pointer to the outer query.
** The subquery is p->pSrc->a[iFrom].  isAgg is true if the outer query
** uses aggregates.
**
** If flattening is not attempted, this routine is a no-op and returns 0.

    isOuterJoin = 1;
  }

  assert( pSubSrc->nSrc>0 );  /* True by restriction (7) */
  if( iFrom>0 && (pSubSrc->a[0].fg.jointype & JT_LTORJ)!=0 ){
    return 0;   /* Restriction (27a) */
  }



  /* Condition (28) is blocked by the caller */
  assert( !pSubitem->fg.isCte || pSubitem->u2.pCteUse->eM10d!=M10d_Yes );

  /* Restriction (17): If the sub-query is a compound SELECT, then it must
  ** use only the UNION ALL operator. And none of the simple select queries
  ** that make up the compound SELECT are allowed to be aggregate or distinct
  ** queries.
  */
  if( pSub->pPrior ){

    /* Catch mismatch in the declared columns of a view and the number of
    ** columns in the SELECT on the RHS */
    if( pTab->nCol!=pSub->pEList->nExpr ){
      sqlite3ErrorMsg(pParse, "expected %d columns for '%s' but got %d",
                      pTab->nCol, pTab->zName, pSub->pEList->nExpr);
      goto select_end;
    }

    /* Do not attempt the usual optimizations (flattening and ORDER BY
    ** elimination) on a MATERIALIZED common table expression because
    ** a MATERIALIZED common table expression is an optimization fence.
    */
    if( pItem->fg.isCte && pItem->u2.pCteUse->eM10d==M10d_Yes ){
      continue;
    }

    /* Do not try to flatten an aggregate subquery.
    **
    ** Flattening an aggregate subquery is only possible if the outer query
    ** is not a join.  But if the outer query is not a join, then the subquery
    ** will be implemented as a co-routine and there is no advantage to
    ** flattening in that case.

    **    (4)   The outer query uses an aggregate function other than
    **          the built-in count(), min(), or max().
    **    (5)   The ORDER BY isn't going to accomplish anything because
    **          one of:
    **            (a)  The outer query has a different ORDER BY clause
    **            (b)  The subquery is part of a join
    **          See forum post 062d576715d277c8
    **
    ** Also retain the ORDER BY if the OmitOrderBy optimization is disabled.
    */
    if( pSub->pOrderBy!=0
     && (p->pOrderBy!=0 || pTabList->nSrc>1)      /* Condition (5) */
     && pSub->pLimit==0                           /* Condition (1) */
     && (pSub->selFlags & SF_OrderByReqd)==0      /* Condition (2) */
     && (p->selFlags & SF_OrderByReqd)==0         /* Condition (3) and (4) */
     && OptimizationEnabled(db, SQLITE_OmitOrderBy)

      */
      flags = WHERE_ONEPASS_DESIRED;
      if( !pParse->nested
       && !pTrigger
       && !hasFK
       && !chngKey
       && !bReplace
       && (pWhere==0 || !ExprHasProperty(pWhere, EP_Subquery))
      ){
        flags |= WHERE_ONEPASS_MULTIROW;
      }
      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere,0,0,0,flags,iIdxCur);
      if( pWInfo==0 ) goto update_cleanup;

      /* A one-pass strategy that might update more than one row may not

     && p->nOut<=pTemplate->nOut                      /* (2c) */
    ){
      return 0;  /* Discard pTemplate */
    }

    /* If pTemplate is always better than p, then cause p to be overwritten
    ** with pTemplate.  pTemplate is better than p if:
    **   (1)  pTemplate has no more dependencies than p, and
    **   (2)  pTemplate has an equal or lower cost than p.
    */
    if( (p->prereq & pTemplate->prereq)==pTemplate->prereq   /* (1)  */
     && p->rRun>=pTemplate->rRun                             /* (2a) */
     && p->nOut>=pTemplate->nOut                             /* (2b) */
    ){
      assert( p->rSetup>=pTemplate->rSetup ); /* SETUP-INVARIANT above */

  pParse = pWInfo->pParse;
  nLoop = pWInfo->nLevel;
  /* TUNING: For simple queries, only the best path is tracked.
  ** For 2-way joins, the 5 best paths are followed.
  ** For joins of 3 or more tables, track the 10 best paths */
  mxChoice = (nLoop<=1) ? 1 : (nLoop==2 ? 5 : 10);
  assert( nLoop<=pWInfo->pTabList->nSrc );
  WHERETRACE(0x002, ("---- begin solver.  (nRowEst=%d, nQueryLoop=%d)\n",
                     nRowEst, pParse->nQueryLoop));

  /* If nRowEst is zero and there is an ORDER BY clause, ignore it. In this
  ** case the purpose of this call is to estimate the number of rows returned
  ** by the overall query. Once this estimate has been obtained, the caller
  ** will invoke this function a second time, passing the estimate as the
  ** nRowEst parameter.  */
  if( pWInfo->pOrderBy==0 || nRowEst==0 ){

        }else{
          rCost = rUnsorted;
          rUnsorted -= 2;  /* TUNING:  Slight bias in favor of no-sort plans */
        }

        /* TUNING:  A full-scan of a VIEW or subquery in the outer loop
        ** is not so bad. */
        if( iLoop==0 && (pWLoop->wsFlags & WHERE_VIEWSCAN)!=0 && nLoop>1 ){
          rCost += -10;
          nOut += -30;
          WHERETRACE(0x80,("VIEWSCAN cost reduction for %c\n",pWLoop->cId));
        }

        /* Check to see if pWLoop should be added to the set of
        ** mxChoice best-so-far paths.
        **
        ** First look for an existing path among best-so-far paths
        ** that covers the same set of loops and has the same isOrdered

#endif
    pParse->pIdxEpr = p;
    if( p->pIENext==0 ){
      sqlite3ParserAddCleanup(pParse, whereIndexedExprCleanup, pParse);
    }
  }
}

/*
** Set the reverse-scan order mask to one for all tables in the query
** with the exception of MATERIALIZED common table expressions that have
** their own internal ORDER BY clauses.
**
** This implements the PRAGMA reverse_unordered_selects=ON setting.
** (Also SQLITE_DBCONFIG_REVERSE_SCANORDER).
*/
static SQLITE_NOINLINE void whereReverseScanOrder(WhereInfo *pWInfo){
  int ii;
  for(ii=0; ii<pWInfo->pTabList->nSrc; ii++){
    SrcItem *pItem = &pWInfo->pTabList->a[ii];
    if( !pItem->fg.isCte
     || pItem->u2.pCteUse->eM10d!=M10d_Yes
     || NEVER(pItem->pSelect==0)
     || pItem->pSelect->pOrderBy==0
    ){
      pWInfo->revMask |= MASKBIT(ii);
    }
  }
}

/*
** Generate the beginning of the loop used for WHERE clause processing.
** The return value is a pointer to an opaque structure that contains
** information needed to terminate the loop.  Later, the calling routine
** should invoke sqlite3WhereEnd() with the return value of this function
** in order to complete the WHERE clause processing.

    wherePathSolver(pWInfo, 0);
    if( db->mallocFailed ) goto whereBeginError;
    if( pWInfo->pOrderBy ){
       wherePathSolver(pWInfo, pWInfo->nRowOut+1);
       if( db->mallocFailed ) goto whereBeginError;
    }
  }
  assert( pWInfo->pTabList!=0 );
  if( pWInfo->pOrderBy==0 && (db->flags & SQLITE_ReverseOrder)!=0 ){
    whereReverseScanOrder(pWInfo);
  }
  if( pParse->nErr ){
    goto whereBeginError;
  }
  assert( db->mallocFailed==0 );
#ifdef WHERETRACE_ENABLED
  if( sqlite3WhereTrace ){

    int wsFlags = pWInfo->a[0].pWLoop->wsFlags;
    int bOnerow = (wsFlags & WHERE_ONEROW)!=0;
    assert( !(wsFlags & WHERE_VIRTUALTABLE) || IsVirtual(pTabList->a[0].pTab) );
    if( bOnerow || (
        0!=(wctrlFlags & WHERE_ONEPASS_MULTIROW)
     && !IsVirtual(pTabList->a[0].pTab)
     && (0==(wsFlags & WHERE_MULTI_OR) || (wctrlFlags & WHERE_DUPLICATES_OK))
     && OptimizationEnabled(db, SQLITE_OnePass)
    )){
      pWInfo->eOnePass = bOnerow ? ONEPASS_SINGLE : ONEPASS_MULTI;
      if( HasRowid(pTabList->a[0].pTab) && (wsFlags & WHERE_IDX_ONLY) ){
        if( wctrlFlags & WHERE_ONEPASS_MULTIROW ){
          bFordelete = OPFLAG_FORDELETE;
        }
        pWInfo->a[0].pWLoop->wsFlags = (wsFlags & ~WHERE_IDX_ONLY);

  **     { ... }           // User supplied code
  **  #line <lineno> <thisfile>
  **     break;
  */
/********** Begin reduce actions **********************************************/
        YYMINORTYPE yylhsminor;
      case 0: /* explain ::= EXPLAIN */
{ if( pParse->pReprepare==0 ) pParse->explain = 1; }
        break;
      case 1: /* explain ::= EXPLAIN QUERY PLAN */
{ if( pParse->pReprepare==0 ) pParse->explain = 2; }
        break;
      case 2: /* cmdx ::= cmd */
{ sqlite3FinishCoding(pParse); }
        break;
      case 3: /* cmd ::= BEGIN transtype trans_opt */
{sqlite3BeginTransaction(pParse, yymsp[-1].minor.yy394);}
        break;

/*
** Growing our own isspace() routine this way is twice as fast as
** the library isspace() function, resulting in a 7% overall performance
** increase for the parser.  (Ubuntu14.10 gcc 4.8.4 x64 with -Os).
*/
static const char jsonIsSpace[] = {
  0, 0, 0, 0, 0, 0, 0, 0,  0, 1, 1, 0, 0, 1, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  1, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,

  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
};
#define fast_isspace(x) (jsonIsSpace[(unsigned char)x])

/*
** Characters that are special to JSON.  Control charaters,
** '"' and '\\'.
*/
static const char jsonIsOk[256] = {
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
  1, 1, 0, 1, 1, 1, 1, 0,  1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 0, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,

  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1,  1, 1, 1, 1, 1, 1, 1, 1
};


#if !defined(SQLITE_DEBUG) && !defined(SQLITE_COVERAGE_TEST)
#  define VVA(X)
#else
#  define VVA(X) X
#endif

/* Objects */
typedef struct JsonString JsonString;
typedef struct JsonNode JsonNode;
typedef struct JsonParse JsonParse;
typedef struct JsonCleanup JsonCleanup;

/* An instance of this object represents a JSON string
** under construction.  Really, this is a generic string accumulator
** that can be and is used to create strings other than JSON.
*/
struct JsonString {
  sqlite3_context *pCtx;   /* Function context - put error messages here */
  char *zBuf;              /* Append JSON content here */
  u64 nAlloc;              /* Bytes of storage available in zBuf[] */
  u64 nUsed;               /* Bytes of zBuf[] currently used */
  u8 bStatic;              /* True if zBuf is static space */
  u8 bErr;                 /* True if an error has been encountered */
  char zSpace[100];        /* Initial static space */
};

/* A deferred cleanup task.  A list of JsonCleanup objects might be
** run when the JsonParse object is destroyed.
*/
struct JsonCleanup {
  JsonCleanup *pJCNext;    /* Next in a list */
  void (*xOp)(void*);      /* Routine to run */
  void *pArg;              /* Argument to xOp() */
};

/* JSON type values
*/
#define JSON_SUBST    0    /* Special edit node.  Uses u.iPrev */
#define JSON_NULL     1
#define JSON_TRUE     2
#define JSON_FALSE    3
#define JSON_INT      4
#define JSON_REAL     5
#define JSON_STRING   6
#define JSON_ARRAY    7
#define JSON_OBJECT   8

/* The "subtype" set for JSON values */
#define JSON_SUBTYPE  74    /* Ascii for "J" */

/*
** Names of the various JSON types:
*/
static const char * const jsonType[] = {
  "subst",
  "null", "true", "false", "integer", "real", "text", "array", "object"
};

/* Bit values for the JsonNode.jnFlag field
*/
#define JNODE_RAW     0x01  /* Content is raw, not JSON encoded */
#define JNODE_ESCAPE  0x02  /* Content is text with \ escapes */
#define JNODE_REMOVE  0x04  /* Do not output */
#define JNODE_REPLACE 0x08  /* Target of a JSON_SUBST node */

#define JNODE_APPEND  0x10  /* More ARRAY/OBJECT entries at u.iAppend */
#define JNODE_LABEL   0x20  /* Is a label of an object */
#define JNODE_JSON5   0x40  /* Node contains JSON5 enhancements */


/* A single node of parsed JSON.  An array of these nodes describes
** a parse of JSON + edits.
**
** Use the json_parse() SQL function (available when compiled with
** -DSQLITE_DEBUG) to see a dump of complete JsonParse objects, including
** a complete listing and decoding of the array of JsonNodes.
*/
struct JsonNode {
  u8 eType;              /* One of the JSON_ type values */
  u8 jnFlags;            /* JNODE flags */
  u8 eU;                 /* Which union element to use */
  u32 n;                 /* Bytes of content for INT, REAL or STRING
                         ** Number of sub-nodes for ARRAY and OBJECT
                         ** Node that SUBST applies to */
  union {
    const char *zJContent; /* 1: Content for INT, REAL, and STRING */
    u32 iAppend;           /* 2: More terms for ARRAY and OBJECT */
    u32 iKey;              /* 3: Key for ARRAY objects in json_tree() */
    u32 iPrev;             /* 4: Previous SUBST node, or 0 */

  } u;
};


/* A parsed and possibly edited JSON string.  Lifecycle:
**
**   1.  JSON comes in and is parsed into an array aNode[].  The original
**       JSON text is stored in zJson.
**
**   2.  Zero or more changes are made (via json_remove() or json_replace()
**       or similar) to the aNode[] array.
**
**   3.  A new, edited and mimified JSON string is generated from aNode
**       and stored in zAlt.  The JsonParse object always owns zAlt.
**
** Step 1 always happens.  Step 2 and 3 may or may not happen, depending
** on the operation.
**
** aNode[].u.zJContent entries typically point into zJson.  Hence zJson
** must remain valid for the lifespan of the parse.  For edits,
** aNode[].u.zJContent might point to malloced space other than zJson.
** Entries in pClup are responsible for freeing that extra malloced space.
**
** When walking the parse tree in aNode[], edits are ignored if useMod is
** false.
*/
struct JsonParse {
  u32 nNode;         /* Number of slots of aNode[] used */
  u32 nAlloc;        /* Number of slots of aNode[] allocated */
  JsonNode *aNode;   /* Array of nodes containing the parse */
  char *zJson;       /* Original JSON string (before edits) */
  char *zAlt;        /* Revised and/or mimified JSON */
  u32 *aUp;          /* Index of parent of each node */
  JsonCleanup *pClup;/* Cleanup operations prior to freeing this object */
  u16 iDepth;        /* Nesting depth */
  u8 nErr;           /* Number of errors seen */
  u8 oom;            /* Set to true if out of memory */
  u8 bJsonIsRCStr;   /* True if zJson is an RCStr */
  u8 hasNonstd;      /* True if input uses non-standard features like JSON5 */
  u8 useMod;         /* Actually use the edits contain inside aNode */
  u8 hasMod;         /* aNode contains edits from the original zJson */
  u32 nJPRef;        /* Number of references to this object */
  int nJson;         /* Length of the zJson string in bytes */
  int nAlt;          /* Length of alternative JSON string zAlt, in bytes */
  u32 iErr;          /* Error location in zJson[] */
  u32 iSubst;        /* Last JSON_SUBST entry in aNode[] */
  u32 iHold;         /* Age of this entry in the cache for LRU replacement */
};

/*
** Maximum nesting depth of JSON for this implementation.
**
** This limit is needed to avoid a stack overflow in the recursive
** descent parser.  A depth of 1000 is far deeper than any sane JSON

*/
static void jsonInit(JsonString *p, sqlite3_context *pCtx){
  p->pCtx = pCtx;
  p->bErr = 0;
  jsonZero(p);
}


/* Free all allocated memory and reset the JsonString object back to its
** initial state.
*/
static void jsonReset(JsonString *p){
  if( !p->bStatic ) sqlite3RCStrUnref(p->zBuf);
  jsonZero(p);
}


/* Report an out-of-memory (OOM) condition
*/
static void jsonOom(JsonString *p){
  p->bErr = 1;
  sqlite3_result_error_nomem(p->pCtx);
  jsonReset(p);
}

/* Enlarge pJson->zBuf so that it can hold at least N more bytes.
** Return zero on success.  Return non-zero on an OOM error
*/
static int jsonGrow(JsonString *p, u32 N){
  u64 nTotal = N<p->nAlloc ? p->nAlloc*2 : p->nAlloc+N+10;
  char *zNew;
  if( p->bStatic ){
    if( p->bErr ) return 1;
    zNew = sqlite3RCStrNew(nTotal);
    if( zNew==0 ){
      jsonOom(p);
      return SQLITE_NOMEM;
    }
    memcpy(zNew, p->zBuf, (size_t)p->nUsed);
    p->zBuf = zNew;
    p->bStatic = 0;
  }else{
    p->zBuf = sqlite3RCStrResize(p->zBuf, nTotal);
    if( p->zBuf==0 ){
      p->bErr = 1;
      jsonZero(p);
      return SQLITE_NOMEM;
    }

  }
  p->nAlloc = nTotal;
  return SQLITE_OK;
}

/* Append N bytes from zIn onto the end of the JsonString string.
*/
static SQLITE_NOINLINE void jsonAppendExpand(
  JsonString *p,
  const char *zIn,
  u32 N
){
  assert( N>0 );
  if( jsonGrow(p,N) ) return;
  memcpy(p->zBuf+p->nUsed, zIn, N);
  p->nUsed += N;
}
static void jsonAppendRaw(JsonString *p, const char *zIn, u32 N){
  if( N==0 ) return;
  if( N+p->nUsed >= p->nAlloc ){
    jsonAppendExpand(p,zIn,N);
  }else{
    memcpy(p->zBuf+p->nUsed, zIn, N);
    p->nUsed += N;
  }
}
static void jsonAppendRawNZ(JsonString *p, const char *zIn, u32 N){
  assert( N>0 );
  if( N+p->nUsed >= p->nAlloc ){
    jsonAppendExpand(p,zIn,N);
  }else{
    memcpy(p->zBuf+p->nUsed, zIn, N);
    p->nUsed += N;
  }
}


/* Append formatted text (not to exceed N bytes) to the JsonString.
*/
static void jsonPrintf(int N, JsonString *p, const char *zFormat, ...){
  va_list ap;
  if( (p->nUsed + N >= p->nAlloc) && jsonGrow(p, N) ) return;
  va_start(ap, zFormat);
  sqlite3_vsnprintf(N, p->zBuf+p->nUsed, zFormat, ap);
  va_end(ap);
  p->nUsed += (int)strlen(p->zBuf+p->nUsed);
}

/* Append a single character
*/
static SQLITE_NOINLINE void jsonAppendCharExpand(JsonString *p, char c){
  if( jsonGrow(p,1) ) return;
  p->zBuf[p->nUsed++] = c;
}
static void jsonAppendChar(JsonString *p, char c){
  if( p->nUsed>=p->nAlloc ){
    jsonAppendCharExpand(p,c);
  }else{
    p->zBuf[p->nUsed++] = c;
  }
}

/* Try to force the string to be a zero-terminated RCStr string.
**
** Return true on success.  Return false if an OOM prevents this
** from happening.
*/
static int jsonForceRCStr(JsonString *p){
  jsonAppendChar(p, 0);
  if( p->bErr ) return 0;
  p->nUsed--;
  if( p->bStatic==0 ) return 1;
  p->nAlloc = 0;
  p->nUsed++;
  jsonGrow(p, p->nUsed);
  p->nUsed--;
  return p->bStatic==0;
}


/* Append a comma separator to the output buffer, if the previous
** character is not '[' or '{'.
*/
static void jsonAppendSeparator(JsonString *p){
  char c;
  if( p->nUsed==0 ) return;
  c = p->zBuf[p->nUsed-1];
  if( c=='[' || c=='{' ) return;
  jsonAppendChar(p, ',');
}

/* Append the N-byte string in zIn to the end of the JsonString string
** under construction.  Enclose the string in "..." and escape
** any double-quotes or backslash characters contained within the
** string.
*/
static void jsonAppendString(JsonString *p, const char *zIn, u32 N){
  u32 i;
  if( zIn==0 || ((N+p->nUsed+2 >= p->nAlloc) && jsonGrow(p,N+2)!=0) ) return;
  p->zBuf[p->nUsed++] = '"';
  for(i=0; i<N; i++){
    unsigned char c = ((unsigned const char*)zIn)[i];
    if( jsonIsOk[c] ){
      p->zBuf[p->nUsed++] = c;
    }else if( c=='"' || c=='\\' ){
      json_simple_escape:
      if( (p->nUsed+N+3-i > p->nAlloc) && jsonGrow(p,N+3-i)!=0 ) return;
      p->zBuf[p->nUsed++] = '\\';
      p->zBuf[p->nUsed++] = c;
    }else if( c=='\'' ){
      p->zBuf[p->nUsed++] = c;
    }else{
      static const char aSpecial[] = {
         0, 0, 0, 0, 0, 0, 0, 0, 'b', 't', 'n', 0, 'f', 'r', 0, 0,
         0, 0, 0, 0, 0, 0, 0, 0,   0,   0,   0, 0,   0,   0, 0, 0
      };
      assert( sizeof(aSpecial)==32 );
      assert( aSpecial['\b']=='b' );
      assert( aSpecial['\f']=='f' );
      assert( aSpecial['\n']=='n' );
      assert( aSpecial['\r']=='r' );
      assert( aSpecial['\t']=='t' );
      assert( c>=0 && c<sizeof(aSpecial) );
      if( aSpecial[c] ){
        c = aSpecial[c];
        goto json_simple_escape;
      }
      if( (p->nUsed+N+7+i > p->nAlloc) && jsonGrow(p,N+7-i)!=0 ) return;
      p->zBuf[p->nUsed++] = '\\';
      p->zBuf[p->nUsed++] = 'u';
      p->zBuf[p->nUsed++] = '0';
      p->zBuf[p->nUsed++] = '0';
      p->zBuf[p->nUsed++] = "0123456789abcdef"[c>>4];
      p->zBuf[p->nUsed++] = "0123456789abcdef"[c&0xf];
    }

  }
  p->zBuf[p->nUsed++] = '"';
  assert( p->nUsed<p->nAlloc );
}

/*
** The zIn[0..N] string is a JSON5 string literal.  Append to p a translation
** of the string literal that standard JSON and that omits all JSON5
** features.
*/
static void jsonAppendNormalizedString(JsonString *p, const char *zIn, u32 N){
  u32 i;
  jsonAppendChar(p, '"');
  zIn++;
  N -= 2;
  while( N>0 ){
    for(i=0; i<N && zIn[i]!='\\'; i++){}
    if( i>0 ){
      jsonAppendRawNZ(p, zIn, i);
      zIn += i;
      N -= i;
      if( N==0 ) break;
    }
    assert( zIn[0]=='\\' );
    switch( (u8)zIn[1] ){
      case '\'':
        jsonAppendChar(p, '\'');
        break;
      case 'v':
        jsonAppendRawNZ(p, "\\u0009", 6);
        break;
      case 'x':
        jsonAppendRawNZ(p, "\\u00", 4);
        jsonAppendRawNZ(p, &zIn[2], 2);
        zIn += 2;
        N -= 2;
        break;
      case '0':
        jsonAppendRawNZ(p, "\\u0000", 6);
        break;
      case '\r':
        if( zIn[2]=='\n' ){
          zIn++;
          N--;
        }
        break;
      case '\n':
        break;
      case 0xe2:
        assert( N>=4 );
        assert( 0x80==(u8)zIn[2] );
        assert( 0xa8==(u8)zIn[3] || 0xa9==(u8)zIn[3] );
        zIn += 2;
        N -= 2;
        break;
      default:
        jsonAppendRawNZ(p, zIn, 2);
        break;
    }
    zIn += 2;
    N -= 2;
  }
  jsonAppendChar(p, '"');
}

  if( zIn[0]=='0' && (zIn[1]=='x' || zIn[1]=='X') ){
    sqlite3_int64 i = 0;
    int rc = sqlite3DecOrHexToI64(zIn, &i);
    if( rc<=1 ){
      jsonPrintf(100,p,"%lld",i);
    }else{
      assert( rc==2 );
      jsonAppendRawNZ(p, "9.0e999", 7);
    }
    return;
  }
  assert( N>0 );
  jsonAppendRawNZ(p, zIn, N);
}

/*
** The zIn[0..N] string is a JSON5 real literal.  Append to p a translation
** of the string literal that standard JSON and that omits all JSON5
** features.
*/

      zIn += i;
      N -= i;
      jsonAppendChar(p, '0');
      break;
    }
  }
  if( N>0 ){
    jsonAppendRawNZ(p, zIn, N);
  }
}



/*
** Append a function parameter value to the JSON string under
** construction.
*/
static void jsonAppendValue(
  JsonString *p,                 /* Append to this JSON string */
  sqlite3_value *pValue          /* Value to append */
){
  switch( sqlite3_value_type(pValue) ){
    case SQLITE_NULL: {
      jsonAppendRawNZ(p, "null", 4);
      break;
    }
    case SQLITE_FLOAT: {
      jsonPrintf(100, p, "%!0.15g", sqlite3_value_double(pValue));
      break;
    }
    case SQLITE_INTEGER: {

      break;
    }
  }
}


/* Make the JSON in p the result of the SQL function.
**
** The JSON string is reset.
*/
static void jsonResult(JsonString *p){
  if( p->bErr==0 ){
    if( p->bStatic ){
      sqlite3_result_text64(p->pCtx, p->zBuf, p->nUsed,
                            SQLITE_TRANSIENT, SQLITE_UTF8);
    }else if( jsonForceRCStr(p) ){
      sqlite3RCStrRef(p->zBuf);
      sqlite3_result_text64(p->pCtx, p->zBuf, p->nUsed,
                            (void(*)(void*))sqlite3RCStrUnref,
                            SQLITE_UTF8);

    }
  }
  if( p->bErr==1 ){
    sqlite3_result_error_nomem(p->pCtx);
  }
  jsonReset(p);
}

/**************************************************************************
** Utility routines for dealing with JsonNode and JsonParse objects
**************************************************************************/

/*

}

/*
** Reclaim all memory allocated by a JsonParse object.  But do not
** delete the JsonParse object itself.
*/
static void jsonParseReset(JsonParse *pParse){
  while( pParse->pClup ){
    JsonCleanup *pTask = pParse->pClup;
    pParse->pClup = pTask->pJCNext;
    pTask->xOp(pTask->pArg);
    sqlite3_free(pTask);
  }
  assert( pParse->nJPRef<=1 );
  if( pParse->aNode ){
    sqlite3_free(pParse->aNode);
    pParse->aNode = 0;
  }
  pParse->nNode = 0;
  pParse->nAlloc = 0;
  if( pParse->aUp ){
    sqlite3_free(pParse->aUp);
    pParse->aUp = 0;
  }
  if( pParse->bJsonIsRCStr ){
    sqlite3RCStrUnref(pParse->zJson);
    pParse->zJson = 0;
    pParse->bJsonIsRCStr = 0;
  }
  if( pParse->zAlt ){
    sqlite3RCStrUnref(pParse->zAlt);
    pParse->zAlt = 0;
  }
}

/*
** Free a JsonParse object that was obtained from sqlite3_malloc().
**
** Note that destroying JsonParse might call sqlite3RCStrUnref() to
** destroy the zJson value.  The RCStr object might recursively invoke
** JsonParse to destroy this pParse object again.  Take care to ensure
** that this recursive destructor sequence terminates harmlessly.
*/
static void jsonParseFree(JsonParse *pParse){
  if( pParse->nJPRef>1 ){
    pParse->nJPRef--;
  }else{
    jsonParseReset(pParse);
    sqlite3_free(pParse);
  }
}

/*
** Add a cleanup task to the JsonParse object.
**
** If an OOM occurs, the cleanup operation happens immediately
** and this function returns SQLITE_NOMEM.
*/
static int jsonParseAddCleanup(
  JsonParse *pParse,          /* Add the cleanup task to this parser */
  void(*xOp)(void*),          /* The cleanup task */
  void *pArg                  /* Argument to the cleanup */
){
  JsonCleanup *pTask = sqlite3_malloc64( sizeof(*pTask) );
  if( pTask==0 ){
    pParse->oom = 1;
    xOp(pArg);
    return SQLITE_ERROR;
  }
  pTask->pJCNext = pParse->pClup;
  pParse->pClup = pTask;
  pTask->xOp = xOp;
  pTask->pArg = pArg;
  return SQLITE_OK;
}

/*
** Convert the JsonNode pNode into a pure JSON string and
** append to pOut.  Subsubstructure is also included.  Return
** the number of JsonNode objects that are encoded.
*/
static void jsonRenderNode(
  JsonParse *pParse,             /* the complete parse of the JSON */
  JsonNode *pNode,               /* The node to render */
  JsonString *pOut               /* Write JSON here */

){
  assert( pNode!=0 );

  while( (pNode->jnFlags & JNODE_REPLACE)!=0 && pParse->useMod ){
    u32 idx = (u32)(pNode - pParse->aNode);
    u32 i = pParse->iSubst;
    while( 1 /*exit-by-break*/ ){
      assert( i<pParse->nNode );
      assert( pParse->aNode[i].eType==JSON_SUBST );
      assert( pParse->aNode[i].eU==4 );
      assert( pParse->aNode[i].u.iPrev<i );
      if( pParse->aNode[i].n==idx ){
        pNode = &pParse->aNode[i+1];
        break;
      }
      i = pParse->aNode[i].u.iPrev;

    }
  }
  switch( pNode->eType ){
    default: {
      assert( pNode->eType==JSON_NULL );
      jsonAppendRawNZ(pOut, "null", 4);
      break;
    }
    case JSON_TRUE: {
      jsonAppendRawNZ(pOut, "true", 4);
      break;
    }
    case JSON_FALSE: {
      jsonAppendRawNZ(pOut, "false", 5);
      break;
    }
    case JSON_STRING: {
      assert( pNode->eU==1 );
      if( pNode->jnFlags & JNODE_RAW ){
        if( pNode->jnFlags & JNODE_LABEL ){
          jsonAppendChar(pOut, '"');
          jsonAppendRaw(pOut, pNode->u.zJContent, pNode->n);
          jsonAppendChar(pOut, '"');
        }else{
          jsonAppendString(pOut, pNode->u.zJContent, pNode->n);
        }
      }else if( pNode->jnFlags & JNODE_JSON5 ){
        jsonAppendNormalizedString(pOut, pNode->u.zJContent, pNode->n);
      }else{
        assert( pNode->n>0 );
        jsonAppendRawNZ(pOut, pNode->u.zJContent, pNode->n);
      }
      break;
    }
    case JSON_REAL: {
      assert( pNode->eU==1 );
      if( pNode->jnFlags & JNODE_JSON5 ){
        jsonAppendNormalizedReal(pOut, pNode->u.zJContent, pNode->n);
      }else{
        assert( pNode->n>0 );
        jsonAppendRawNZ(pOut, pNode->u.zJContent, pNode->n);
      }
      break;
    }
    case JSON_INT: {
      assert( pNode->eU==1 );
      if( pNode->jnFlags & JNODE_JSON5 ){
        jsonAppendNormalizedInt(pOut, pNode->u.zJContent, pNode->n);
      }else{
        assert( pNode->n>0 );
        jsonAppendRawNZ(pOut, pNode->u.zJContent, pNode->n);
      }
      break;
    }
    case JSON_ARRAY: {
      u32 j = 1;
      jsonAppendChar(pOut, '[');
      for(;;){
        while( j<=pNode->n ){
          if( (pNode[j].jnFlags & JNODE_REMOVE)==0 || pParse->useMod==0 ){
            jsonAppendSeparator(pOut);
            jsonRenderNode(pParse, &pNode[j], pOut);
          }
          j += jsonNodeSize(&pNode[j]);
        }
        if( (pNode->jnFlags & JNODE_APPEND)==0 ) break;
        if( pParse->useMod==0 ) break;
        assert( pNode->eU==2 );
        pNode = &pParse->aNode[pNode->u.iAppend];
        j = 1;
      }
      jsonAppendChar(pOut, ']');
      break;
    }
    case JSON_OBJECT: {
      u32 j = 1;
      jsonAppendChar(pOut, '{');
      for(;;){
        while( j<=pNode->n ){
          if( (pNode[j+1].jnFlags & JNODE_REMOVE)==0 || pParse->useMod==0 ){
            jsonAppendSeparator(pOut);
            jsonRenderNode(pParse, &pNode[j], pOut);
            jsonAppendChar(pOut, ':');
            jsonRenderNode(pParse, &pNode[j+1], pOut);
          }
          j += 1 + jsonNodeSize(&pNode[j+1]);
        }
        if( (pNode->jnFlags & JNODE_APPEND)==0 ) break;
        if( pParse->useMod==0 ) break;
        assert( pNode->eU==2 );
        pNode = &pParse->aNode[pNode->u.iAppend];
        j = 1;
      }
      jsonAppendChar(pOut, '}');
      break;
    }
  }
}

/*
** Return a JsonNode and all its descendants as a JSON string.
*/
static void jsonReturnJson(
  JsonParse *pParse,          /* The complete JSON */
  JsonNode *pNode,            /* Node to return */
  sqlite3_context *pCtx,      /* Return value for this function */

  int bGenerateAlt            /* Also store the rendered text in zAlt */
){
  JsonString s;
  if( pParse->oom ){
    sqlite3_result_error_nomem(pCtx);
    return;
  }
  if( pParse->nErr==0 ){
    jsonInit(&s, pCtx);
    jsonRenderNode(pParse, pNode, &s);
    if( bGenerateAlt && pParse->zAlt==0 && jsonForceRCStr(&s) ){
      pParse->zAlt = sqlite3RCStrRef(s.zBuf);
      pParse->nAlt = s.nUsed;
    }
    jsonResult(&s);
    sqlite3_result_subtype(pCtx, JSON_SUBTYPE);
  }
}

/*
** Translate a single byte of Hex into an integer.
** This routine only works if h really is a valid hexadecimal
** character:  0..9a..fA..F
*/

  return v;
}

/*
** Make the JsonNode the return value of the function.
*/
static void jsonReturn(
  JsonParse *pParse,          /* Complete JSON parse tree */
  JsonNode *pNode,            /* Node to return */
  sqlite3_context *pCtx       /* Return value for this function */

){
  switch( pNode->eType ){
    default: {
      assert( pNode->eType==JSON_NULL );
      sqlite3_result_null(pCtx);
      break;
    }
    case JSON_TRUE: {
      sqlite3_result_int(pCtx, 1);
      break;
    }
    case JSON_FALSE: {
      sqlite3_result_int(pCtx, 0);
      break;
    }
    case JSON_INT: {
      sqlite3_int64 i = 0;
      int rc;
      int bNeg = 0;
      const char *z;


      assert( pNode->eU==1 );
      z = pNode->u.zJContent;
      if( z[0]=='-' ){ z++; bNeg = 1; }
      else if( z[0]=='+' ){ z++; }
      rc = sqlite3DecOrHexToI64(z, &i);
      if( rc<=1 ){

        zOut[j] = 0;
        sqlite3_result_text(pCtx, zOut, j, sqlite3_free);
      }
      break;
    }
    case JSON_ARRAY:
    case JSON_OBJECT: {
      jsonReturnJson(pParse, pNode, pCtx, 0);
      break;
    }
  }
}

/* Forward reference */
static int jsonParseAddNode(JsonParse*,u32,u32,const char*);

#elif defined(_MSC_VER) && _MSC_VER>=1310
#  define JSON_NOINLINE  __declspec(noinline)
#else
#  define JSON_NOINLINE
#endif


/*
** Add a single node to pParse->aNode after first expanding the
** size of the aNode array.  Return the index of the new node.
**
** If an OOM error occurs, set pParse->oom and return -1.
*/
static JSON_NOINLINE int jsonParseAddNodeExpand(
  JsonParse *pParse,        /* Append the node to this object */
  u32 eType,                /* Node type */
  u32 n,                    /* Content size or sub-node count */
  const char *zContent      /* Content */
){
  u32 nNew;
  JsonNode *pNew;
  assert( pParse->nNode>=pParse->nAlloc );
  if( pParse->oom ) return -1;
  nNew = pParse->nAlloc*2 + 10;
  pNew = sqlite3_realloc64(pParse->aNode, sizeof(JsonNode)*nNew);
  if( pNew==0 ){
    pParse->oom = 1;
    return -1;
  }
  pParse->nAlloc = sqlite3_msize(pNew)/sizeof(JsonNode);
  pParse->aNode = pNew;
  assert( pParse->nNode<pParse->nAlloc );
  return jsonParseAddNode(pParse, eType, n, zContent);
}

/*
** Create a new JsonNode instance based on the arguments and append that
** instance to the JsonParse.  Return the index in pParse->aNode[] of the
** new node, or -1 if a memory allocation fails.
*/
static int jsonParseAddNode(
  JsonParse *pParse,        /* Append the node to this object */
  u32 eType,                /* Node type */
  u32 n,                    /* Content size or sub-node count */
  const char *zContent      /* Content */
){
  JsonNode *p;
  assert( pParse->aNode!=0 || pParse->nNode>=pParse->nAlloc );
  if( pParse->nNode>=pParse->nAlloc ){
    return jsonParseAddNodeExpand(pParse, eType, n, zContent);
  }
  p = &pParse->aNode[pParse->nNode];
  p->eType = (u8)(eType & 0xff);
  p->jnFlags = (u8)(eType >> 8);
  VVA( p->eU = zContent ? 1 : 0 );
  p->n = n;
  p->u.zJContent = zContent;
  return pParse->nNode++;
}

/*
** Add an array of new nodes to the current pParse->aNode array.
** Return the index of the first node added.
**
** If an OOM error occurs, set pParse->oom.
*/
static void jsonParseAddNodeArray(
  JsonParse *pParse,        /* Append the node to this object */
  JsonNode *aNode,          /* Array of nodes to add */
  u32 nNode                 /* Number of elements in aNew */
){
  if( pParse->nNode + nNode > pParse->nAlloc ){
    u32 nNew = pParse->nNode + nNode;
    JsonNode *aNew = sqlite3_realloc64(pParse->aNode, nNew*sizeof(JsonNode));
    if( aNew==0 ){
      pParse->oom = 1;
      return;
    }
    pParse->nAlloc = sqlite3_msize(aNew)/sizeof(JsonNode);
    pParse->aNode = aNew;
  }
  memcpy(&pParse->aNode[pParse->nNode], aNode, nNode*sizeof(JsonNode));
  pParse->nNode += nNode;
}

/*
** Add a new JSON_SUBST node.  The node immediately following
** this new node will be the substitute content for iNode.
*/
static int jsonParseAddSubstNode(
  JsonParse *pParse,       /* Add the JSON_SUBST here */
  u32 iNode                /* References this node */
){
  int idx = jsonParseAddNode(pParse, JSON_SUBST, iNode, 0);
  if( pParse->oom ) return -1;
  pParse->aNode[iNode].jnFlags |= JNODE_REPLACE;
  pParse->aNode[idx].eU = 4;
  pParse->aNode[idx].u.iPrev = pParse->iSubst;
  pParse->iSubst = idx;
  pParse->hasMod = 1;
  pParse->useMod = 1;
  return idx;
}

/*
** Return true if z[] begins with 2 (or more) hexadecimal digits
*/
static int jsonIs2Hex(const char *z){
  return sqlite3Isxdigit(z[0]) && sqlite3Isxdigit(z[1]);
}

/*
** Parse a single JSON value which begins at pParse->zJson[i].  Return the
** index of the first character past the end of the value parsed.
**
** Special return values:
**
**      0    End of input
**     -1    Syntax error
**     -2    '}' seen
**     -3    ']' seen
**     -4    ',' seen
**     -5    ':' seen
*/
static int jsonParseValue(JsonParse *pParse, u32 i){

    jnFlags = JNODE_JSON5;
    goto parse_string;
  case '"':
    /* Parse string */
    jnFlags = 0;
  parse_string:
    cDelim = z[i];
    for(j=i+1; 1; j++){
      if( jsonIsOk[(unsigned char)z[j]] ) continue;
      c = z[j];
      if( c==cDelim ){


        break;

      }else if( c=='\\' ){
        c = z[++j];
        if( c=='"' || c=='\\' || c=='/' || c=='b' || c=='f'
           || c=='n' || c=='r' || c=='t'
           || (c=='u' && jsonIs4Hex(&z[j+1])) ){
          jnFlags |= JNODE_ESCAPE;
        }else if( c=='\'' || c=='0' || c=='v' || c=='\n'
           || (0xe2==(u8)c && 0x80==(u8)z[j+1]
                && (0xa8==(u8)z[j+2] || 0xa9==(u8)z[j+2]))
           || (c=='x' && jsonIs2Hex(&z[j+1])) ){
          jnFlags |= (JNODE_ESCAPE|JNODE_JSON5);
          pParse->hasNonstd = 1;
        }else if( c=='\r' ){
          if( z[j+1]=='\n' ) j++;
          jnFlags |= (JNODE_ESCAPE|JNODE_JSON5);
          pParse->hasNonstd = 1;
        }else{
          pParse->iErr = j;
          return -1;
        }
      }else if( c<=0x1f ){
        /* Control characters are not allowed in strings */
        pParse->iErr = j;
        return -1;
      }

    }
    jsonParseAddNode(pParse, JSON_STRING | (jnFlags<<8), j+1-i, &z[i]);
    return j+1;
  }
  case 't': {
    if( strncmp(z+i,"true",4)==0 && !sqlite3Isalnum(z[i+4]) ){
      jsonParseAddNode(pParse, JSON_TRUE, 0, 0);

    return -1;  /* Syntax error */
  }
  } /* End switch(z[i]) */
}

/*
** Parse a complete JSON string.  Return 0 on success or non-zero if there
** are any errors.  If an error occurs, free all memory held by pParse,
** but not pParse itself.
**
** pParse must be initialized to an empty parse object prior to calling
** this routine.
*/
static int jsonParse(
  JsonParse *pParse,           /* Initialize and fill this JsonParse object */
  sqlite3_context *pCtx        /* Report errors here */

){
  int i;


  const char *zJson = pParse->zJson;
  i = jsonParseValue(pParse, 0);
  if( pParse->oom ) i = -1;
  if( i>0 ){
    assert( pParse->iDepth==0 );
    while( fast_isspace(zJson[i]) ) i++;
    if( zJson[i] ){
      i += json5Whitespace(&zJson[i]);

      }
    }
    jsonParseReset(pParse);
    return 1;
  }
  return 0;
}


/* Mark node i of pParse as being a child of iParent.  Call recursively
** to fill in all the descendants of node i.
*/
static void jsonParseFillInParentage(JsonParse *pParse, u32 i, u32 iParent){
  JsonNode *pNode = &pParse->aNode[i];
  u32 j;

/*
** Magic number used for the JSON parse cache in sqlite3_get_auxdata()
*/
#define JSON_CACHE_ID  (-429938)  /* First cache entry */
#define JSON_CACHE_SZ  4          /* Max number of cache entries */

/*
** Obtain a complete parse of the JSON found in the pJson argument
**
** Use the sqlite3_get_auxdata() cache to find a preexisting parse
** if it is available.  If the cache is not available or if it
** is no longer valid, parse the JSON again and return the new parse.
** Also register the new parse so that it will be available for
** future sqlite3_get_auxdata() calls.
**
** If an error occurs and pErrCtx!=0 then report the error on pErrCtx
** and return NULL.
**
** The returned pointer (if it is not NULL) is owned by the cache in
** most cases, not the caller.  The caller does NOT need to invoke
** jsonParseFree(), in most cases.
**
** Except, if an error occurs and pErrCtx==0 then return the JsonParse
** object with JsonParse.nErr non-zero and the caller will own the JsonParse

** object.  In that case, it will be the responsibility of the caller to
** invoke jsonParseFree().  To summarize:
**
**   pErrCtx!=0 || p->nErr==0      ==>   Return value p is owned by the
**                                       cache.  Call does not need to
**                                       free it.
**
**   pErrCtx==0 && p->nErr!=0      ==>   Return value is owned by the caller
**                                       and so the caller must free it.
*/
static JsonParse *jsonParseCached(
  sqlite3_context *pCtx,         /* Context to use for cache search */
  sqlite3_value *pJson,          /* Function param containing JSON text */
  sqlite3_context *pErrCtx,      /* Write parse errors here if not NULL */
  int bUnedited                  /* No prior edits allowed */
){
  char *zJson = (char*)sqlite3_value_text(pJson);
  int nJson = sqlite3_value_bytes(pJson);
  JsonParse *p;
  JsonParse *pMatch = 0;
  int iKey;
  int iMinKey = 0;
  u32 iMinHold = 0xffffffff;
  u32 iMaxHold = 0;
  int bJsonRCStr;

  if( zJson==0 ) return 0;
  for(iKey=0; iKey<JSON_CACHE_SZ; iKey++){
    p = (JsonParse*)sqlite3_get_auxdata(pCtx, JSON_CACHE_ID+iKey);
    if( p==0 ){
      iMinKey = iKey;
      break;
    }
    if( pMatch==0
     && p->nJson==nJson
     && (p->hasMod==0 || bUnedited==0)
     && (p->zJson==zJson || memcmp(p->zJson,zJson,nJson)==0)
    ){
      p->nErr = 0;
      p->useMod = 0;
      pMatch = p;
    }else
    if( pMatch==0
     && p->zAlt!=0
     && bUnedited==0
     && p->nAlt==nJson
     && memcmp(p->zAlt, zJson, nJson)==0
    ){
      p->nErr = 0;
      p->useMod = 1;
      pMatch = p;
    }else if( p->iHold<iMinHold ){
      iMinHold = p->iHold;
      iMinKey = iKey;
    }
    if( p->iHold>iMaxHold ){
      iMaxHold = p->iHold;
    }
  }
  if( pMatch ){
    /* The input JSON text was found in the cache.  Use the preexisting
    ** parse of this JSON */
    pMatch->nErr = 0;
    pMatch->iHold = iMaxHold+1;
    assert( pMatch->nJPRef>0 ); /* pMatch is owned by the cache */
    return pMatch;
  }

  /* The input JSON was not found anywhere in the cache.  We will need
  ** to parse it ourselves and generate a new JsonParse object.
  */
  bJsonRCStr = sqlite3ValueIsOfClass(pJson,(void(*)(void*))sqlite3RCStrUnref);
  p = sqlite3_malloc64( sizeof(*p) + (bJsonRCStr ? 0 : nJson+1) );
  if( p==0 ){
    sqlite3_result_error_nomem(pCtx);
    return 0;
  }
  memset(p, 0, sizeof(*p));
  if( bJsonRCStr ){
    p->zJson = sqlite3RCStrRef(zJson);
    p->bJsonIsRCStr = 1;
  }else{
    p->zJson = (char*)&p[1];
    memcpy(p->zJson, zJson, nJson+1);
  }
  p->nJPRef = 1;
  if( jsonParse(p, pErrCtx) ){
    if( pErrCtx==0 ){
      p->nErr = 1;
      assert( p->nJPRef==1 ); /* Caller will own the new JsonParse object p */
      return p;
    }
    jsonParseFree(p);
    return 0;
  }
  p->nJson = nJson;
  p->iHold = iMaxHold+1;
  /* Transfer ownership of the new JsonParse to the cache */
  sqlite3_set_auxdata(pCtx, JSON_CACHE_ID+iMinKey, p,
                      (void(*)(void*))jsonParseFree);
  return (JsonParse*)sqlite3_get_auxdata(pCtx, JSON_CACHE_ID+iMinKey);
}

/*
** Compare the OBJECT label at pNode against zKey,nKey.  Return true on

  u32 iRoot,              /* Begin the search at this node */
  const char *zPath,      /* The path to search */
  int *pApnd,             /* Append nodes to complete path if not NULL */
  const char **pzErr      /* Make *pzErr point to any syntax error in zPath */
){
  u32 i, j, nKey;
  const char *zKey;
  JsonNode *pRoot;
  if( pParse->oom ) return 0;
  pRoot = &pParse->aNode[iRoot];
  while( (pRoot->jnFlags & JNODE_REPLACE)!=0 && pParse->useMod ){
    u32 idx = (u32)(pRoot - pParse->aNode);
    i = pParse->iSubst;
    while( 1 /*exit-by-break*/ ){
      assert( i<pParse->nNode );
      assert( pParse->aNode[i].eType==JSON_SUBST );
      assert( pParse->aNode[i].eU==4 );
      assert( pParse->aNode[i].u.iPrev<i );
      if( pParse->aNode[i].n==idx ){
        pRoot = &pParse->aNode[i+1];
        iRoot = i+1;
        break;
      }
      i = pParse->aNode[i].u.iPrev;
    }
  }
  if( zPath[0]==0 ) return pRoot;

  if( zPath[0]=='.' ){
    if( pRoot->eType!=JSON_OBJECT ) return 0;
    zPath++;
    if( zPath[0]=='"' ){
      zKey = zPath + 1;
      for(i=1; zPath[i] && zPath[i]!='"'; i++){}
      nKey = i-1;

        if( jsonLabelCompare(pRoot+j, zKey, nKey) ){
          return jsonLookupStep(pParse, iRoot+j+1, &zPath[i], pApnd, pzErr);
        }
        j++;
        j += jsonNodeSize(&pRoot[j]);
      }
      if( (pRoot->jnFlags & JNODE_APPEND)==0 ) break;
      if( pParse->useMod==0 ) break;
      assert( pRoot->eU==2 );
      iRoot = pRoot->u.iAppend;
      pRoot = &pParse->aNode[iRoot];
      j = 1;
    }
    if( pApnd ){
      u32 iStart, iLabel;
      JsonNode *pNode;
      assert( pParse->useMod );
      iStart = jsonParseAddNode(pParse, JSON_OBJECT, 2, 0);
      iLabel = jsonParseAddNode(pParse, JSON_STRING, nKey, zKey);
      zPath += i;
      pNode = jsonLookupAppend(pParse, zPath, pApnd, pzErr);
      if( pParse->oom ) return 0;
      if( pNode ){
        pRoot = &pParse->aNode[iRoot];
        assert( pRoot->eU==0 );
        pRoot->u.iAppend = iStart;
        pRoot->jnFlags |= JNODE_APPEND;
        VVA( pRoot->eU = 2 );
        pParse->aNode[iLabel].jnFlags |= JNODE_RAW;
      }
      return pNode;
    }
  }else if( zPath[0]=='[' ){
    i = 0;
    j = 1;
    while( sqlite3Isdigit(zPath[j]) ){
      i = i*10 + zPath[j] - '0';
      j++;
    }
    if( j<2 || zPath[j]!=']' ){
      if( zPath[1]=='#' ){
        JsonNode *pBase = pRoot;
        int iBase = iRoot;
        if( pRoot->eType!=JSON_ARRAY ) return 0;
        for(;;){
          while( j<=pBase->n ){
            if( (pBase[j].jnFlags & JNODE_REMOVE)==0 || pParse->useMod==0 ) i++;
            j += jsonNodeSize(&pBase[j]);
          }
          if( (pBase->jnFlags & JNODE_APPEND)==0 ) break;
          if( pParse->useMod==0 ) break;
          assert( pBase->eU==2 );
          iBase = pBase->u.iAppend;
          pBase = &pParse->aNode[iBase];
          j = 1;
        }
        j = 2;
        if( zPath[2]=='-' && sqlite3Isdigit(zPath[3]) ){
          unsigned int x = 0;
          j = 3;

        return 0;
      }
    }
    if( pRoot->eType!=JSON_ARRAY ) return 0;
    zPath += j + 1;
    j = 1;
    for(;;){
      while( j<=pRoot->n
         && (i>0 || ((pRoot[j].jnFlags & JNODE_REMOVE)!=0 && pParse->useMod))
      ){
        if( (pRoot[j].jnFlags & JNODE_REMOVE)==0 || pParse->useMod==0 ) i--;
        j += jsonNodeSize(&pRoot[j]);
      }
      if( (pRoot->jnFlags & JNODE_APPEND)==0 ) break;
      if( pParse->useMod==0 ) break;
      assert( pRoot->eU==2 );
      iRoot = pRoot->u.iAppend;
      pRoot = &pParse->aNode[iRoot];
      j = 1;
    }
    if( j<=pRoot->n ){
      return jsonLookupStep(pParse, iRoot+j, zPath, pApnd, pzErr);
    }
    if( i==0 && pApnd ){
      u32 iStart;
      JsonNode *pNode;
      assert( pParse->useMod );
      iStart = jsonParseAddNode(pParse, JSON_ARRAY, 1, 0);
      pNode = jsonLookupAppend(pParse, zPath, pApnd, pzErr);
      if( pParse->oom ) return 0;
      if( pNode ){
        pRoot = &pParse->aNode[iRoot];
        assert( pRoot->eU==0 );
        pRoot->u.iAppend = iStart;
        pRoot->jnFlags |= JNODE_APPEND;
        VVA( pRoot->eU = 2 );
      }
      return pNode;
    }
  }else{
    *pzErr = zPath;

  }
}


/****************************************************************************
** SQL functions used for testing and debugging
****************************************************************************/

#if SQLITE_DEBUG
/*
** Print N node entries.
*/
static void jsonDebugPrintNodeEntries(
  JsonNode *aNode,  /* First node entry to print */
  int N             /* Number of node entries to print */
){
  int i;
  for(i=0; i<N; i++){
    const char *zType;
    if( aNode[i].jnFlags & JNODE_LABEL ){
      zType = "label";
    }else{
      zType = jsonType[aNode[i].eType];
    }
    printf("node %4u: %-7s n=%-5d", i, zType, aNode[i].n);
    if( (aNode[i].jnFlags & ~JNODE_LABEL)!=0 ){
      u8 f = aNode[i].jnFlags;
      if( f & JNODE_RAW )     printf(" RAW");
      if( f & JNODE_ESCAPE )  printf(" ESCAPE");
      if( f & JNODE_REMOVE )  printf(" REMOVE");
      if( f & JNODE_REPLACE ) printf(" REPLACE");
      if( f & JNODE_APPEND )  printf(" APPEND");
      if( f & JNODE_JSON5 )   printf(" JSON5");
    }
    switch( aNode[i].eU ){
      case 1:  printf(" zJContent=[%.*s]\n",
                      aNode[i].n, aNode[i].u.zJContent);           break;
      case 2:  printf(" iAppend=%u\n", aNode[i].u.iAppend);        break;
      case 3:  printf(" iKey=%u\n", aNode[i].u.iKey);              break;
      case 4:  printf(" iPrev=%u\n", aNode[i].u.iPrev);            break;
      default: printf("\n");
    }
  }
}
#endif /* SQLITE_DEBUG */


#if 0  /* 1 for debugging.  0 normally.  Requires -DSQLITE_DEBUG too */
static void jsonDebugPrintParse(JsonParse *p){
  jsonDebugPrintNodeEntries(p->aNode, p->nNode);
}
static void jsonDebugPrintNode(JsonNode *pNode){
  jsonDebugPrintNodeEntries(pNode, jsonNodeSize(pNode));
}
#else
   /* The usual case */
# define jsonDebugPrintNode(X)
# define jsonDebugPrintParse(X)
#endif

#ifdef SQLITE_DEBUG
/*
** SQL function:   json_parse(JSON)
**
** Parse JSON using jsonParseCached().  Then print a dump of that
** parse on standard output.  Return the mimified JSON result, just
** like the json() function.
*/
static void jsonParseFunc(
  sqlite3_context *ctx,
  int argc,
  sqlite3_value **argv
){

  JsonParse *p;        /* The parse */


  assert( argc==1 );
  p = jsonParseCached(ctx, argv[0], ctx, 0);
  if( p==0 ) return;

  printf("nNode     = %u\n", p->nNode);
  printf("nAlloc    = %u\n", p->nAlloc);
  printf("nJson     = %d\n", p->nJson);
  printf("nAlt      = %d\n", p->nAlt);
  printf("nErr      = %u\n", p->nErr);
  printf("oom       = %u\n", p->oom);
  printf("hasNonstd = %u\n", p->hasNonstd);
  printf("useMod    = %u\n", p->useMod);
  printf("hasMod    = %u\n", p->hasMod);
  printf("nJPRef    = %u\n", p->nJPRef);

  printf("iSubst    = %u\n", p->iSubst);









  printf("iHold     = %u\n", p->iHold);

  jsonDebugPrintNodeEntries(p->aNode, p->nNode);
  jsonReturnJson(p, p->aNode, ctx, 1);
}

/*
** The json_test1(JSON) function return true (1) if the input is JSON
** text generated by another json function.  It returns (0) if the input
** is not known to be JSON.
*/

  sqlite3_value **argv
){
  JsonParse *p;          /* The parse */
  sqlite3_int64 n = 0;
  u32 i;
  JsonNode *pNode;

  p = jsonParseCached(ctx, argv[0], ctx, 0);
  if( p==0 ) return;
  assert( p->nNode );
  if( argc==2 ){
    const char *zPath = (const char*)sqlite3_value_text(argv[1]);
    pNode = jsonLookup(p, zPath, 0, ctx);
  }else{
    pNode = p->aNode;
  }
  if( pNode==0 ){
    return;
  }
  if( pNode->eType==JSON_ARRAY ){
    while( 1 /*exit-by-break*/ ){
      for(i=1; i<=pNode->n; n++){
        i += jsonNodeSize(&pNode[i]);
      }
      if( (pNode->jnFlags & JNODE_APPEND)==0 ) break;
      if( p->useMod==0 ) break;
      assert( pNode->eU==2 );
      pNode = &p->aNode[pNode->u.iAppend];
    }
  }
  sqlite3_result_int64(ctx, n);
}

/*
** Bit values for the flags passed into jsonExtractFunc() or

  JsonParse *p;          /* The parse */
  JsonNode *pNode;
  const char *zPath;
  int flags = SQLITE_PTR_TO_INT(sqlite3_user_data(ctx));
  JsonString jx;

  if( argc<2 ) return;
  p = jsonParseCached(ctx, argv[0], ctx, 0);
  if( p==0 ) return;
  if( argc==2 ){
    /* With a single PATH argument */
    zPath = (const char*)sqlite3_value_text(argv[1]);
    if( zPath==0 ) return;
    if( flags & JSON_ABPATH ){
      if( zPath[0]!='$' || (zPath[1]!='.' && zPath[1]!='[' && zPath[1]!=0) ){
        /* The -> and ->> operators accept abbreviated PATH arguments.  This
        ** is mostly for compatibility with PostgreSQL, but also for
        ** convenience.
        **
        **     NUMBER   ==>  $[NUMBER]     // PG compatible
        **     LABEL    ==>  $.LABEL       // PG compatible
        **     [NUMBER] ==>  $[NUMBER]     // Not PG.  Purely for convenience
        */
        jsonInit(&jx, ctx);
        if( sqlite3Isdigit(zPath[0]) ){
          jsonAppendRawNZ(&jx, "$[", 2);
          jsonAppendRaw(&jx, zPath, (int)strlen(zPath));
          jsonAppendRawNZ(&jx, "]", 2);
        }else{
          jsonAppendRawNZ(&jx, "$.", 1 + (zPath[0]!='['));
          jsonAppendRaw(&jx, zPath, (int)strlen(zPath));
          jsonAppendChar(&jx, 0);
        }
        pNode = jx.bErr ? 0 : jsonLookup(p, jx.zBuf, 0, ctx);
        jsonReset(&jx);
      }else{
        pNode = jsonLookup(p, zPath, 0, ctx);
      }
      if( pNode ){
        if( flags & JSON_JSON ){
          jsonReturnJson(p, pNode, ctx, 0);
        }else{
          jsonReturn(p, pNode, ctx);
          sqlite3_result_subtype(ctx, 0);
        }
      }
    }else{
      pNode = jsonLookup(p, zPath, 0, ctx);
      if( p->nErr==0 && pNode ) jsonReturn(p, pNode, ctx);
    }
  }else{
    /* Two or more PATH arguments results in a JSON array with each
    ** element of the array being the value selected by one of the PATHs */
    int i;
    jsonInit(&jx, ctx);
    jsonAppendChar(&jx, '[');
    for(i=1; i<argc; i++){
      zPath = (const char*)sqlite3_value_text(argv[i]);
      pNode = jsonLookup(p, zPath, 0, ctx);
      if( p->nErr ) break;
      jsonAppendSeparator(&jx);
      if( pNode ){
        jsonRenderNode(p, pNode, &jx);
      }else{
        jsonAppendRawNZ(&jx, "null", 4);
      }
    }
    if( i==argc ){
      jsonAppendChar(&jx, ']');
      jsonResult(&jx);
      sqlite3_result_subtype(ctx, JSON_SUBTYPE);
    }

    assert( pPatch[i].eU==1 );
    nKey = pPatch[i].n;
    zKey = pPatch[i].u.zJContent;
    for(j=1; j<pTarget->n; j += jsonNodeSize(&pTarget[j+1])+1 ){
      assert( pTarget[j].eType==JSON_STRING );
      assert( pTarget[j].jnFlags & JNODE_LABEL );
      if( jsonSameLabel(&pPatch[i], &pTarget[j]) ){
        if( pTarget[j+1].jnFlags & (JNODE_REMOVE|JNODE_REPLACE) ) break;
        if( pPatch[i+1].eType==JSON_NULL ){
          pTarget[j+1].jnFlags |= JNODE_REMOVE;
        }else{
          JsonNode *pNew = jsonMergePatch(pParse, iTarget+j+1, &pPatch[i+1]);
          if( pNew==0 ) return 0;
          if( pNew!=&pParse->aNode[iTarget+j+1] ){


            jsonParseAddSubstNode(pParse, iTarget+j+1);




            jsonParseAddNodeArray(pParse, pNew, jsonNodeSize(pNew));

          }
          pTarget = &pParse->aNode[iTarget];
        }
        break;
      }
    }
    if( j>=pTarget->n && pPatch[i+1].eType!=JSON_NULL ){
      int iStart;
      JsonNode *pApnd;
      u32 nApnd;
      iStart = jsonParseAddNode(pParse, JSON_OBJECT, 0, 0);
      jsonParseAddNode(pParse, JSON_STRING, nKey, zKey);
      pApnd = &pPatch[i+1];
      if( pApnd->eType==JSON_OBJECT ) jsonRemoveAllNulls(pApnd);
      nApnd = jsonNodeSize(pApnd);
      jsonParseAddNodeArray(pParse, pApnd, jsonNodeSize(pApnd));
      if( pParse->oom ) return 0;

      pParse->aNode[iStart].n = 1+nApnd;

      pParse->aNode[iRoot].jnFlags |= JNODE_APPEND;
      pParse->aNode[iRoot].u.iAppend = iStart;
      VVA( pParse->aNode[iRoot].eU = 2 );

      iRoot = iStart;

      pTarget = &pParse->aNode[iTarget];


    }
  }
  return pTarget;
}

/*
** Implementation of the json_mergepatch(JSON1,JSON2) function.  Return a JSON
** object that is the result of running the RFC 7396 MergePatch() algorithm
** on the two arguments.
*/
static void jsonPatchFunc(
  sqlite3_context *ctx,
  int argc,
  sqlite3_value **argv
){
  JsonParse *pX;     /* The JSON that is being patched */
  JsonParse *pY;     /* The patch */
  JsonNode *pResult;   /* The result of the merge */

  UNUSED_PARAMETER(argc);
  pX = jsonParseCached(ctx, argv[0], ctx, 1);
  if( pX==0 ) return;
  assert( pX->hasMod==0 );
  pX->hasMod = 1;
  pY = jsonParseCached(ctx, argv[1], ctx, 1);
  if( pY==0 ) return;

  pX->useMod = 1;
  pY->useMod = 1;
  pResult = jsonMergePatch(pX, 0, pY->aNode);
  assert( pResult!=0 || pX->oom );
  if( pResult && pX->oom==0 ){
    jsonDebugPrintParse(pX);
    jsonDebugPrintNode(pResult);
    jsonReturnJson(pX, pResult, ctx, 0);
  }else{
    sqlite3_result_error_nomem(ctx);
  }


}


/*
** Implementation of the json_object(NAME,VALUE,...) function.  Return a JSON
** object that contains all name/value given in arguments.  Or if any name
** is not a string or if any value is a BLOB, throw an error.

** JSON or PATH arguments result in an error.
*/
static void jsonRemoveFunc(
  sqlite3_context *ctx,
  int argc,
  sqlite3_value **argv
){
  JsonParse *pParse;          /* The parse */
  JsonNode *pNode;
  const char *zPath;
  u32 i;

  if( argc<1 ) return;
  pParse = jsonParseCached(ctx, argv[0], ctx, argc>1);
  if( pParse==0 ) return;
  for(i=1; i<(u32)argc; i++){
    zPath = (const char*)sqlite3_value_text(argv[i]);
    if( zPath==0 ) goto remove_done;
    pNode = jsonLookup(pParse, zPath, 0, ctx);
    if( pParse->nErr ) goto remove_done;
    if( pNode ){
      pNode->jnFlags |= JNODE_REMOVE;
      pParse->hasMod = 1;
      pParse->useMod = 1;
    }
  }
  if( (pParse->aNode[0].jnFlags & JNODE_REMOVE)==0 ){
    jsonReturnJson(pParse, pParse->aNode, ctx, 1);
  }
remove_done:
  jsonDebugPrintParse(p);
}

/*
** Substitute the value at iNode with the pValue parameter.
*/
static void jsonReplaceNode(
  sqlite3_context *pCtx,
  JsonParse *p,
  int iNode,
  sqlite3_value *pValue
){
  int idx = jsonParseAddSubstNode(p, iNode);
  if( idx<=0 ){
    assert( p->oom );
    return;
  }
  switch( sqlite3_value_type(pValue) ){
    case SQLITE_NULL: {
      jsonParseAddNode(p, JSON_NULL, 0, 0);
      break;
    }
    case SQLITE_FLOAT: {
      char *z = sqlite3_mprintf("%!0.15g", sqlite3_value_double(pValue));
      int n;
      if( z==0 ){
        p->oom = 1;
        break;
      }
      n = sqlite3Strlen30(z);
      jsonParseAddNode(p, JSON_REAL, n, z);
      jsonParseAddCleanup(p, sqlite3_free, z);
      break;
    }
    case SQLITE_INTEGER: {
      char *z = sqlite3_mprintf("%lld", sqlite3_value_int64(pValue));
      int n;
      if( z==0 ){
        p->oom = 1;
        break;
      }
      n = sqlite3Strlen30(z);
      jsonParseAddNode(p, JSON_INT, n, z);
      jsonParseAddCleanup(p, sqlite3_free, z);

      break;
    }
    case SQLITE_TEXT: {
      const char *z = (const char*)sqlite3_value_text(pValue);
      u32 n = (u32)sqlite3_value_bytes(pValue);
      if( z==0 ){
         p->oom = 1;
         break;
      }
      if( sqlite3_value_subtype(pValue)!=JSON_SUBTYPE ){
        char *zCopy = sqlite3DbStrDup(0, z);
        int k;
        if( zCopy ){
          jsonParseAddCleanup(p, sqlite3_free, zCopy);
       }else{
          p->oom = 1;
          sqlite3_result_error_nomem(pCtx);
        }
        k = jsonParseAddNode(p, JSON_STRING, n, zCopy);
        assert( k>0 || p->oom );
        if( p->oom==0 ) p->aNode[k].jnFlags |= JNODE_RAW;
      }else{
        JsonParse *pPatch = jsonParseCached(pCtx, pValue, pCtx, 1);
        if( pPatch==0 ){
          p->oom = 1;
          break;
        }
        jsonParseAddNodeArray(p, pPatch->aNode, pPatch->nNode);
        /* The nodes copied out of pPatch and into p likely contain
        ** u.zJContent pointers into pPatch->zJson.  So preserve the
        ** content of pPatch until p is destroyed. */
        assert( pPatch->nJPRef>=1 );
        pPatch->nJPRef++;
        jsonParseAddCleanup(p, (void(*)(void*))jsonParseFree, pPatch);
      }
      break;
    }
    default: {
      jsonParseAddNode(p, JSON_NULL, 0, 0);
      sqlite3_result_error(pCtx, "JSON cannot hold BLOB values", -1);
      p->nErr++;
      break;
    }
  }
}

/*
** json_replace(JSON, PATH, VALUE, ...)
**
** Replace the value at PATH with VALUE.  If PATH does not already exist,
** this routine is a no-op.  If JSON or PATH is malformed, throw an error.
*/
static void jsonReplaceFunc(
  sqlite3_context *ctx,
  int argc,
  sqlite3_value **argv
){
  JsonParse *pParse;          /* The parse */
  JsonNode *pNode;
  const char *zPath;
  u32 i;

  if( argc<1 ) return;
  if( (argc&1)==0 ) {
    jsonWrongNumArgs(ctx, "replace");
    return;
  }
  pParse = jsonParseCached(ctx, argv[0], ctx, argc>1);
  if( pParse==0 ) return;
  for(i=1; i<(u32)argc; i+=2){
    zPath = (const char*)sqlite3_value_text(argv[i]);
    pParse->useMod = 1;
    pNode = jsonLookup(pParse, zPath, 0, ctx);
    if( pParse->nErr ) goto replace_err;
    if( pNode ){




      jsonReplaceNode(ctx, pParse, (u32)(pNode - pParse->aNode), argv[i+1]);
    }
  }




  jsonReturnJson(pParse, pParse->aNode, ctx, 1);

replace_err:
  jsonDebugPrintParse(pParse);
}


/*
** json_set(JSON, PATH, VALUE, ...)
**
** Set the value at PATH to VALUE.  Create the PATH if it does not already
** exist.  Overwrite existing values that do exist.
** If JSON or PATH is malformed, throw an error.
**
** json_insert(JSON, PATH, VALUE, ...)
**
** Create PATH and initialize it to VALUE.  If PATH already exists, this
** routine is a no-op.  If JSON or PATH is malformed, throw an error.
*/
static void jsonSetFunc(
  sqlite3_context *ctx,
  int argc,
  sqlite3_value **argv
){
  JsonParse *pParse;       /* The parse */
  JsonNode *pNode;
  const char *zPath;
  u32 i;
  int bApnd;
  int bIsSet = sqlite3_user_data(ctx)!=0;

  if( argc<1 ) return;
  if( (argc&1)==0 ) {
    jsonWrongNumArgs(ctx, bIsSet ? "set" : "insert");
    return;
  }
  pParse = jsonParseCached(ctx, argv[0], ctx, argc>1);
  if( pParse==0 ) return;
  for(i=1; i<(u32)argc; i+=2){
    zPath = (const char*)sqlite3_value_text(argv[i]);
    bApnd = 0;
    pParse->useMod = 1;
    pNode = jsonLookup(pParse, zPath, &bApnd, ctx);
    if( pParse->oom ){
      sqlite3_result_error_nomem(ctx);
      goto jsonSetDone;
    }else if( pParse->nErr ){
      goto jsonSetDone;
    }else if( pNode && (bApnd || bIsSet) ){




      jsonReplaceNode(ctx, pParse, (u32)(pNode - pParse->aNode), argv[i+1]);
    }
  }



  jsonDebugPrintParse(pParse);
  jsonReturnJson(pParse, pParse->aNode, ctx, 1);

jsonSetDone:

  /* no cleanup required */;
}

/*
** json_type(JSON)
** json_type(JSON, PATH)
**
** Return the top-level "type" of a JSON string.  json_type() raises an
** error if either the JSON or PATH inputs are not well-formed.
*/
static void jsonTypeFunc(
  sqlite3_context *ctx,
  int argc,
  sqlite3_value **argv
){
  JsonParse *p;          /* The parse */
  const char *zPath;
  JsonNode *pNode;

  p = jsonParseCached(ctx, argv[0], ctx, 0);
  if( p==0 ) return;
  if( argc==2 ){
    zPath = (const char*)sqlite3_value_text(argv[1]);
    pNode = jsonLookup(p, zPath, 0, ctx);
  }else{
    pNode = p->aNode;
  }

  sqlite3_context *ctx,
  int argc,
  sqlite3_value **argv
){
  JsonParse *p;          /* The parse */
  UNUSED_PARAMETER(argc);
  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
  p = jsonParseCached(ctx, argv[0], 0, 0);
  if( p==0 || p->oom ){
    sqlite3_result_error_nomem(ctx);
    sqlite3_free(p);
  }else{
    sqlite3_result_int(ctx, p->nErr==0 && (p->hasNonstd==0 || p->useMod));
    if( p->nErr ) jsonParseFree(p);
  }
}

/*
** json_error_position(JSON)
**

  sqlite3_context *ctx,
  int argc,
  sqlite3_value **argv
){
  JsonParse *p;          /* The parse */
  UNUSED_PARAMETER(argc);
  if( sqlite3_value_type(argv[0])==SQLITE_NULL ) return;
  p = jsonParseCached(ctx, argv[0], 0, 0);
  if( p==0 || p->oom ){
    sqlite3_result_error_nomem(ctx);
    sqlite3_free(p);
  }else if( p->nErr==0 ){
    sqlite3_result_int(ctx, 0);
  }else{
    int n = 1;
    u32 i;
    const char *z = (const char*)sqlite3_value_text(argv[0]);
    for(i=0; i<p->iErr && ALWAYS(z[i]); i++){
      if( (z[i]&0xc0)!=0x80 ) n++;
    }
    sqlite3_result_int(ctx, n);
    jsonParseFree(p);
  }
}

    pStr->pCtx = ctx;
    jsonAppendChar(pStr, ']');
    if( pStr->bErr ){
      if( pStr->bErr==1 ) sqlite3_result_error_nomem(ctx);
      assert( pStr->bStatic );
    }else if( isFinal ){
      sqlite3_result_text(ctx, pStr->zBuf, (int)pStr->nUsed,
                          pStr->bStatic ? SQLITE_TRANSIENT :
                              (void(*)(void*))sqlite3RCStrUnref);
      pStr->bStatic = 1;
    }else{
      sqlite3_result_text(ctx, pStr->zBuf, (int)pStr->nUsed, SQLITE_TRANSIENT);
      pStr->nUsed--;
    }
  }else{
    sqlite3_result_text(ctx, "[]", 2, SQLITE_STATIC);

  if( pStr ){
    jsonAppendChar(pStr, '}');
    if( pStr->bErr ){
      if( pStr->bErr==1 ) sqlite3_result_error_nomem(ctx);
      assert( pStr->bStatic );
    }else if( isFinal ){
      sqlite3_result_text(ctx, pStr->zBuf, (int)pStr->nUsed,
                          pStr->bStatic ? SQLITE_TRANSIENT :
                          (void(*)(void*))sqlite3RCStrUnref);
      pStr->bStatic = 1;
    }else{
      sqlite3_result_text(ctx, pStr->zBuf, (int)pStr->nUsed, SQLITE_TRANSIENT);
      pStr->nUsed--;
    }
  }else{
    sqlite3_result_text(ctx, "{}", 2, SQLITE_STATIC);

  }
  return rc;
}

/* Reset a JsonEachCursor back to its original state.  Free any memory
** held. */
static void jsonEachCursorReset(JsonEachCursor *p){

  sqlite3_free(p->zRoot);
  jsonParseReset(&p->sParse);
  p->iRowid = 0;
  p->i = 0;
  p->iEnd = 0;
  p->eType = 0;
  p->zJson = 0;

){
  JsonEachCursor *p = (JsonEachCursor*)cur;
  JsonNode *pThis = &p->sParse.aNode[p->i];
  switch( i ){
    case JEACH_KEY: {
      if( p->i==0 ) break;
      if( p->eType==JSON_OBJECT ){
        jsonReturn(&p->sParse, pThis, ctx);
      }else if( p->eType==JSON_ARRAY ){
        u32 iKey;
        if( p->bRecursive ){
          if( p->iRowid==0 ) break;
          assert( p->sParse.aNode[p->sParse.aUp[p->i]].eU==3 );
          iKey = p->sParse.aNode[p->sParse.aUp[p->i]].u.iKey;
        }else{
          iKey = p->iRowid;
        }
        sqlite3_result_int64(ctx, (sqlite3_int64)iKey);
      }
      break;
    }
    case JEACH_VALUE: {
      if( pThis->jnFlags & JNODE_LABEL ) pThis++;
      jsonReturn(&p->sParse, pThis, ctx);
      break;
    }
    case JEACH_TYPE: {
      if( pThis->jnFlags & JNODE_LABEL ) pThis++;
      sqlite3_result_text(ctx, jsonType[pThis->eType], -1, SQLITE_STATIC);
      break;
    }
    case JEACH_ATOM: {
      if( pThis->jnFlags & JNODE_LABEL ) pThis++;
      if( pThis->eType>=JSON_ARRAY ) break;
      jsonReturn(&p->sParse, pThis, ctx);
      break;
    }
    case JEACH_ID: {
      sqlite3_result_int64(ctx,
         (sqlite3_int64)p->i + ((pThis->jnFlags & JNODE_LABEL)!=0));
      break;
    }

  UNUSED_PARAMETER(idxStr);
  UNUSED_PARAMETER(argc);
  jsonEachCursorReset(p);
  if( idxNum==0 ) return SQLITE_OK;
  z = (const char*)sqlite3_value_text(argv[0]);
  if( z==0 ) return SQLITE_OK;
  memset(&p->sParse, 0, sizeof(p->sParse));
  p->sParse.nJPRef = 1;
  if( sqlite3ValueIsOfClass(argv[0], (void(*)(void*))sqlite3RCStrUnref) ){
    p->sParse.zJson = sqlite3RCStrRef((char*)z);
  }else{
    n = sqlite3_value_bytes(argv[0]);
    p->sParse.zJson = sqlite3RCStrNew( n+1 );
    if( p->sParse.zJson==0 ) return SQLITE_NOMEM;
    memcpy(p->sParse.zJson, z, (size_t)n+1);
  }
  p->sParse.bJsonIsRCStr = 1;
  p->zJson = p->sParse.zJson;
  if( jsonParse(&p->sParse, 0) ){
    int rc = SQLITE_NOMEM;
    if( p->sParse.oom==0 ){
      sqlite3_free(cur->pVtab->zErrMsg);
      cur->pVtab->zErrMsg = sqlite3_mprintf("malformed JSON");
      if( cur->pVtab->zErrMsg ) rc = SQLITE_ERROR;
    }
    jsonEachCursorReset(p);

        /* assert( db->pPreUpdate->pNewUnpacked || db->pPreUpdate->aNew ); */
        rc = pSession->hook.xNew(pSession->hook.pCtx, iCol, &pVal);
      }else{
        /* assert( db->pPreUpdate->pUnpacked ); */
        rc = pSession->hook.xOld(pSession->hook.pCtx, iCol, &pVal);
      }
      assert( rc==SQLITE_OK );
      (void)rc;                   /* Suppress warning about unused variable */
      if( sqlite3_value_type(pVal)!=eType ) return 0;

      /* A SessionChange object never has a NULL value in a PK column */
      assert( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT
           || eType==SQLITE_BLOB    || eType==SQLITE_TEXT
      );

** And all information loaded from the %_config table.
**
** nAutomerge:
**   The minimum number of segments that an auto-merge operation should
**   attempt to merge together. A value of 1 sets the object to use the
**   compile time default. Zero disables auto-merge altogether.
**
** bContentlessDelete:
**   True if the contentless_delete option was present in the CREATE
**   VIRTUAL TABLE statement.
**
** zContent:
**
** zContentRowid:
**   The value of the content_rowid= option, if one was specified. Or
**   the string "rowid" otherwise. This text is not quoted - if it is
**   used as part of an SQL statement it needs to be quoted appropriately.
**

  char *zName;                    /* Name of FTS index */
  int nCol;                       /* Number of columns */
  char **azCol;                   /* Column names */
  u8 *abUnindexed;                /* True for unindexed columns */
  int nPrefix;                    /* Number of prefix indexes */
  int *aPrefix;                   /* Sizes in bytes of nPrefix prefix indexes */
  int eContent;                   /* An FTS5_CONTENT value */
  int bContentlessDelete;         /* "contentless_delete=" option (dflt==0) */
  char *zContent;                 /* content table */
  char *zContentRowid;            /* "content_rowid=" option value */
  int bColumnsize;                /* "columnsize=" option value (dflt==1) */
  int eDetail;                    /* FTS5_DETAIL_XXX value */
  char *zContentExprlist;
  Fts5Tokenizer *pTok;
  fts5_tokenizer *pTokApi;

  int nAutomerge;                 /* 'automerge' setting */
  int nCrisisMerge;               /* Maximum allowed segments per level */
  int nUsermerge;                 /* 'usermerge' setting */
  int nHashSize;                  /* Bytes of memory for in-memory hash */
  char *zRank;                    /* Name of rank function */
  char *zRankArgs;                /* Arguments to rank function */
  int bSecureDelete;              /* 'secure-delete' */
  int nDeleteMerge;           /* 'deletemerge' */

  /* If non-NULL, points to sqlite3_vtab.base.zErrmsg. Often NULL. */
  char **pzErrmsg;

#ifdef SQLITE_DEBUG
  int bPrefixIndex;               /* True to use prefix-indexes */
#endif

static int sqlite3Fts5IndexReinit(Fts5Index *p);
static int sqlite3Fts5IndexOptimize(Fts5Index *p);
static int sqlite3Fts5IndexMerge(Fts5Index *p, int nMerge);
static int sqlite3Fts5IndexReset(Fts5Index *p);

static int sqlite3Fts5IndexLoadConfig(Fts5Index *p);

static int sqlite3Fts5IndexGetOrigin(Fts5Index *p, i64 *piOrigin);
static int sqlite3Fts5IndexContentlessDelete(Fts5Index *p, i64 iOrigin, i64 iRowid);

/*
** End of interface to code in fts5_index.c.
**************************************************************************/

/**************************************************************************
** Interface to code in fts5_varint.c.
*/

);

/*
** Empty (but do not delete) a hash table.
*/
static void sqlite3Fts5HashClear(Fts5Hash*);

/*
** Return true if the hash is empty, false otherwise.
*/
static int sqlite3Fts5HashIsEmpty(Fts5Hash*);

static int sqlite3Fts5HashQuery(
  Fts5Hash*,                      /* Hash table to query */
  int nPre,
  const char *pTerm, int nTerm,   /* Query term */
  void **ppObj,                   /* OUT: Pointer to doclist for pTerm */
  int *pnDoclist                  /* OUT: Size of doclist in bytes */
);

static int sqlite3Fts5HashScanInit(
  Fts5Hash*,                      /* Hash table to query */
  const char *pTerm, int nTerm    /* Query prefix */
);
static void sqlite3Fts5HashScanNext(Fts5Hash*);
static int sqlite3Fts5HashScanEof(Fts5Hash*);
static void sqlite3Fts5HashScanEntry(Fts5Hash *,
  const char **pzTerm,            /* OUT: term (nul-terminated) */
  const u8 **ppDoclist,           /* OUT: pointer to doclist */
  int *pnDoclist                  /* OUT: size of doclist in bytes */
);



/*
** End of interface to code in fts5_hash.c.
**************************************************************************/

/**************************************************************************

#define FTS5_DEFAULT_PAGE_SIZE   4050
#define FTS5_DEFAULT_AUTOMERGE      4
#define FTS5_DEFAULT_USERMERGE      4
#define FTS5_DEFAULT_CRISISMERGE   16
#define FTS5_DEFAULT_HASHSIZE    (1024*1024)

#define FTS5_DEFAULT_DELETE_AUTOMERGE 10      /* default 10% */

/* Maximum allowed page size */
#define FTS5_MAX_PAGE_SIZE (64*1024)

static int fts5_iswhitespace(char x){
  return (x==' ');
}

        pConfig->zContent = sqlite3Fts5Mprintf(&rc, "%Q.%Q", pConfig->zDb,zArg);
      }else{
        pConfig->eContent = FTS5_CONTENT_NONE;
      }
    }
    return rc;
  }

  if( sqlite3_strnicmp("contentless_delete", zCmd, nCmd)==0 ){
    if( (zArg[0]!='0' && zArg[0]!='1') || zArg[1]!='\0' ){
      *pzErr = sqlite3_mprintf("malformed contentless_delete=... directive");
      rc = SQLITE_ERROR;
    }else{
      pConfig->bContentlessDelete = (zArg[0]=='1');
    }
    return rc;
  }

  if( sqlite3_strnicmp("content_rowid", zCmd, nCmd)==0 ){
    if( pConfig->zContentRowid ){
      *pzErr = sqlite3_mprintf("multiple content_rowid=... directives");
      rc = SQLITE_ERROR;
    }else{
      pConfig->zContentRowid = sqlite3Fts5Strndup(&rc, zArg, -1);

        }
      }
    }

    sqlite3_free(zOne);
    sqlite3_free(zTwo);
  }

  /* We only allow contentless_delete=1 if the table is indeed contentless. */
  if( rc==SQLITE_OK
   && pRet->bContentlessDelete
   && pRet->eContent!=FTS5_CONTENT_NONE
  ){
    *pzErr = sqlite3_mprintf(
        "contentless_delete=1 requires a contentless table"
    );
    rc = SQLITE_ERROR;
  }

  /* We only allow contentless_delete=1 if columnsize=0 is not present.
  **
  ** This restriction may be removed at some point.
  */
  if( rc==SQLITE_OK && pRet->bContentlessDelete && pRet->bColumnsize==0 ){
    *pzErr = sqlite3_mprintf(
        "contentless_delete=1 is incompatible with columnsize=0"
    );
    rc = SQLITE_ERROR;
  }

  /* If a tokenizer= option was successfully parsed, the tokenizer has
  ** already been allocated. Otherwise, allocate an instance of the default
  ** tokenizer (unicode61) now.  */
  if( rc==SQLITE_OK && pRet->pTok==0 ){
    rc = fts5ConfigDefaultTokenizer(pGlobal, pRet);
  }

      *pbBadkey = 1;
    }else{
      if( nCrisisMerge<=1 ) nCrisisMerge = FTS5_DEFAULT_CRISISMERGE;
      if( nCrisisMerge>=FTS5_MAX_SEGMENT ) nCrisisMerge = FTS5_MAX_SEGMENT-1;
      pConfig->nCrisisMerge = nCrisisMerge;
    }
  }

  else if( 0==sqlite3_stricmp(zKey, "deletemerge") ){
    int nVal = -1;
    if( SQLITE_INTEGER==sqlite3_value_numeric_type(pVal) ){
      nVal = sqlite3_value_int(pVal);
    }else{
      *pbBadkey = 1;
    }
    if( nVal<0 ) nVal = FTS5_DEFAULT_DELETE_AUTOMERGE;
    if( nVal>100 ) nVal = 0;
    pConfig->nDeleteMerge = nVal;
  }

  else if( 0==sqlite3_stricmp(zKey, "rank") ){
    const char *zIn = (const char*)sqlite3_value_text(pVal);
    char *zRank;
    char *zRankArgs;
    rc = sqlite3Fts5ConfigParseRank(zIn, &zRank, &zRankArgs);
    if( rc==SQLITE_OK ){

  /* Set default values */
  pConfig->pgsz = FTS5_DEFAULT_PAGE_SIZE;
  pConfig->nAutomerge = FTS5_DEFAULT_AUTOMERGE;
  pConfig->nUsermerge = FTS5_DEFAULT_USERMERGE;
  pConfig->nCrisisMerge = FTS5_DEFAULT_CRISISMERGE;
  pConfig->nHashSize = FTS5_DEFAULT_HASHSIZE;
  pConfig->nDeleteMerge = FTS5_DEFAULT_DELETE_AUTOMERGE;

  zSql = sqlite3Fts5Mprintf(&rc, zSelect, pConfig->zDb, pConfig->zName);
  if( zSql ){
    rc = sqlite3_prepare_v2(pConfig->db, zSql, -1, &p, 0);
    sqlite3_free(zSql);
  }

      pRet = sqlite3Fts5ParseNode(pParse, FTS5_AND, pLeft, pRight, 0);
    }
  }

  return pRet;
}

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
static char *fts5ExprTermPrint(Fts5ExprTerm *pTerm){
  sqlite3_int64 nByte = 0;
  Fts5ExprTerm *p;
  char *zQuoted;

  /* Determine the maximum amount of space required. */
  for(p=pTerm; p; p=p->pSynonym){

    int iCode;
    int bRemoveDiacritics = 0;
    iCode = sqlite3_value_int(apVal[0]);
    if( nArg==2 ) bRemoveDiacritics = sqlite3_value_int(apVal[1]);
    sqlite3_result_int(pCtx, sqlite3Fts5UnicodeFold(iCode, bRemoveDiacritics));
  }
}
#endif /* if SQLITE_TEST || SQLITE_FTS5_DEBUG */

/*
** This is called during initialization to register the fts5_expr() scalar
** UDF with the SQLite handle passed as the only argument.
*/
static int sqlite3Fts5ExprInit(Fts5Global *pGlobal, sqlite3 *db){
#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
  struct Fts5ExprFunc {
    const char *z;
    void (*x)(sqlite3_context*,int,sqlite3_value**);
  } aFunc[] = {
    { "fts5_expr",     fts5ExprFunctionHr },
    { "fts5_expr_tcl", fts5ExprFunctionTcl },
    { "fts5_isalnum",  fts5ExprIsAlnum },

  }

  pList = 0;
  for(i=0; i<nMergeSlot; i++){
    pList = fts5HashEntryMerge(pList, ap[i]);
  }


  sqlite3_free(ap);
  *ppSorted = pList;
  return SQLITE_OK;
}

/*
** Query the hash table for a doclist associated with term pTerm/nTerm.

static int sqlite3Fts5HashScanInit(
  Fts5Hash *p,                    /* Hash table to query */
  const char *pTerm, int nTerm    /* Query prefix */
){
  return fts5HashEntrySort(p, pTerm, nTerm, &p->pScan);
}

#ifdef SQLITE_DEBUG
static int fts5HashCount(Fts5Hash *pHash){
  int nEntry = 0;
  int ii;
  for(ii=0; ii<pHash->nSlot; ii++){
    Fts5HashEntry *p = 0;
    for(p=pHash->aSlot[ii]; p; p=p->pHashNext){
      nEntry++;
    }
  }
  return nEntry;
}
#endif

/*
** Return true if the hash table is empty, false otherwise.
*/
static int sqlite3Fts5HashIsEmpty(Fts5Hash *pHash){
  assert( pHash->nEntry==fts5HashCount(pHash) );
  return pHash->nEntry==0;
}

static void sqlite3Fts5HashScanNext(Fts5Hash *p){
  assert( !sqlite3Fts5HashScanEof(p) );
  p->pScan = p->pScan->pScanNext;
}

static int sqlite3Fts5HashScanEof(Fts5Hash *p){

#if FTS5_MAX_PREFIX_INDEXES > 31
# error "FTS5_MAX_PREFIX_INDEXES is too large"
#endif

#define FTS5_MAX_LEVEL 64

/*
** There are two versions of the format used for the structure record:
**
**   1. the legacy format, that may be read by all fts5 versions, and
**
**   2. the V2 format, which is used by contentless_delete=1 databases.
**
** Both begin with a 4-byte "configuration cookie" value. Then, a legacy
** format structure record contains a varint - the number of levels in
** the structure. Whereas a V2 structure record contains the constant
** 4 bytes [0xff 0x00 0x00 0x01]. This is unambiguous as the value of a
** varint has to be at least 16256 to begin with "0xFF". And the default
** maximum number of levels is 64.
**
** See below for more on structure record formats.
*/
#define FTS5_STRUCTURE_V2 "\xFF\x00\x00\x01"

/*
** Details:
**
** The %_data table managed by this module,
**
**     CREATE TABLE %_data(id INTEGER PRIMARY KEY, block BLOB);
**
** , contains the following 6 types of records. See the comments surrounding
** the FTS5_*_ROWID macros below for a description of how %_data rowids are
** assigned to each fo them.
**
** 1. Structure Records:
**
**   The set of segments that make up an index - the index structure - are
**   recorded in a single record within the %_data table. The record consists
**   of a single 32-bit configuration cookie value followed by a list of
**   SQLite varints.


**
**   If the structure record is a V2 record, the configuration cookie is
**   followed by the following 4 bytes: [0xFF 0x00 0x00 0x01].
**
**   Next, the record continues with three varints:
**
**     + number of levels,
**     + total number of segments on all levels,
**     + value of write counter.
**
**   Then, for each level from 0 to nMax:
**
**     + number of input segments in ongoing merge.
**     + total number of segments in level.
**     + for each segment from oldest to newest:
**         + segment id (always > 0)
**         + first leaf page number (often 1, always greater than 0)
**         + final leaf page number
**
**      Then, for V2 structures only:
**
**         + lower origin counter value,
**         + upper origin counter value,
**         + the number of tombstone hash pages.
**
** 2. The Averages Record:
**
**   A single record within the %_data table. The data is a list of varints.
**   The first value is the number of rows in the index. Then, for each column
**   from left to right, the total number of tokens in the column for all
**   rows of the table.
**

**     * Page number of first child page. As a varint.
**
**     * Copy of first rowid on page indicated by previous field. As a varint.
**
**     * A list of delta-encoded varints - the first rowid on each subsequent
**       child page.
**
** 6. Tombstone Hash Page
**
**   These records are only ever present in contentless_delete=1 tables.
**   There are zero or more of these associated with each segment. They
**   are used to store the tombstone rowids for rows contained in the
**   associated segments.
**
**   The set of nHashPg tombstone hash pages associated with a single
**   segment together form a single hash table containing tombstone rowids.
**   To find the page of the hash on which a key might be stored:
**
**       iPg = (rowid % nHashPg)
**
**   Then, within page iPg, which has nSlot slots:
**
**       iSlot = (rowid / nHashPg) % nSlot
**
**   Each tombstone hash page begins with an 8 byte header:
**
**     1-byte:  Key-size (the size in bytes of each slot). Either 4 or 8.
**     1-byte:  rowid-0-tombstone flag. This flag is only valid on the
**              first tombstone hash page for each segment (iPg=0). If set,
**              the hash table contains rowid 0. If clear, it does not.
**              Rowid 0 is handled specially.
**     2-bytes: unused.
**     4-bytes: Big-endian integer containing number of entries on page.
**
**   Following this are nSlot 4 or 8 byte slots (depending on the key-size
**   in the first byte of the page header). The number of slots may be
**   determined based on the size of the page record and the key-size:
**
**     nSlot = (nByte - 8) / key-size
*/

/*
** Rowids for the averages and structure records in the %_data table.
*/
#define FTS5_AVERAGES_ROWID     1    /* Rowid used for the averages record */
#define FTS5_STRUCTURE_ROWID   10    /* The structure record */

 ((i64)(dlidx)  << (FTS5_DATA_PAGE_B + FTS5_DATA_HEIGHT_B)) +                  \
 ((i64)(height) << (FTS5_DATA_PAGE_B)) +                                       \
 ((i64)(pgno))                                                                 \
)

#define FTS5_SEGMENT_ROWID(segid, pgno)       fts5_dri(segid, 0, 0, pgno)
#define FTS5_DLIDX_ROWID(segid, height, pgno) fts5_dri(segid, 1, height, pgno)
#define FTS5_TOMBSTONE_ROWID(segid,ipg)       fts5_dri(segid+(1<<16), 0, 0, ipg)

#ifdef SQLITE_DEBUG
static int sqlite3Fts5Corrupt() { return SQLITE_CORRUPT_VTAB; }
#endif


/*

  u8 *p;                          /* Pointer to buffer containing record */
  int nn;                         /* Size of record in bytes */
  int szLeaf;                     /* Size of leaf without page-index */
};

/*
** One object per %_data table.
**
** nContentlessDelete:
**   The number of contentless delete operations since the most recent
**   call to fts5IndexFlush() or fts5IndexDiscardData(). This is tracked
**   so that extra auto-merge work can be done by fts5IndexFlush() to
**   account for the delete operations.
*/
struct Fts5Index {
  Fts5Config *pConfig;            /* Virtual table configuration */
  char *zDataTbl;                 /* Name of %_data table */
  int nWorkUnit;                  /* Leaf pages in a "unit" of work */

  /*
  ** Variables related to the accumulation of tokens and doclists within the
  ** in-memory hash tables before they are flushed to disk.
  */
  Fts5Hash *pHash;                /* Hash table for in-memory data */
  int nPendingData;               /* Current bytes of pending data */
  i64 iWriteRowid;                /* Rowid for current doc being written */
  int bDelete;                    /* Current write is a delete */
  int nContentlessDelete;         /* Number of contentless delete ops */
  int nPendingRow;                /* Number of INSERT in hash table */

  /* Error state. */
  int rc;                         /* Current error code */

  /* State used by the fts5DataXXX() functions. */
  sqlite3_blob *pReader;          /* RO incr-blob open on %_data table */
  sqlite3_stmt *pWriter;          /* "INSERT ... %_data VALUES(?,?)" */

  int nSize;
};

/*
** The contents of the "structure" record for each index are represented
** using an Fts5Structure record in memory. Which uses instances of the
** other Fts5StructureXXX types as components.
**
** nOriginCntr:
**   This value is set to non-zero for structure records created for
**   contentlessdelete=1 tables only. In that case it represents the
**   origin value to apply to the next top-level segment created.
*/
struct Fts5StructureSegment {
  int iSegid;                     /* Segment id */
  int pgnoFirst;                  /* First leaf page number in segment */
  int pgnoLast;                   /* Last leaf page number in segment */

  /* contentlessdelete=1 tables only: */
  u64 iOrigin1;
  u64 iOrigin2;
  int nPgTombstone;               /* Number of tombstone hash table pages */
  u64 nEntryTombstone;            /* Number of tombstone entries that "count" */
  u64 nEntry;                     /* Number of rows in this segment */
};
struct Fts5StructureLevel {
  int nMerge;                     /* Number of segments in incr-merge */
  int nSeg;                       /* Total number of segments on level */
  Fts5StructureSegment *aSeg;     /* Array of segments. aSeg[0] is oldest. */
};
struct Fts5Structure {
  int nRef;                       /* Object reference count */
  u64 nWriteCounter;              /* Total leaves written to level 0 */
  u64 nOriginCntr;                /* Origin value for next top-level segment */
  int nSegment;                   /* Total segments in this structure */
  int nLevel;                     /* Number of levels in this index */
  Fts5StructureLevel aLevel[1];   /* Array of nLevel level objects */
};

/*
** An object of type Fts5SegWriter is used to write to segments.

**
**     For each rowid on the page corresponding to the current term, the
**     corresponding aRowidOffset[] entry is set to the byte offset of the
**     start of the "position-list-size" field within the page.
**
** iTermIdx:
**     Index of current term on iTermLeafPgno.
**
** apTombstone/nTombstone:
**     These are used for contentless_delete=1 tables only. When the cursor
**     is first allocated, the apTombstone[] array is allocated so that it
**     is large enough for all tombstones hash pages associated with the
**     segment. The pages themselves are loaded lazily from the database as
**     they are required.
*/
struct Fts5SegIter {
  Fts5StructureSegment *pSeg;     /* Segment to iterate through */
  int flags;                      /* Mask of configuration flags */
  int iLeafPgno;                  /* Current leaf page number */
  Fts5Data *pLeaf;                /* Current leaf data */
  Fts5Data *pNextLeaf;            /* Leaf page (iLeafPgno+1) */
  i64 iLeafOffset;                /* Byte offset within current leaf */
  Fts5Data **apTombstone;         /* Array of tombstone pages */
  int nTombstone;

  /* Next method */
  void (*xNext)(Fts5Index*, Fts5SegIter*, int*);

  /* The page and offset from which the current term was read. The offset
  ** is the offset of the first rowid in the current doclist.  */
  int iTermLeafPgno;

  aOut[0] = (iVal>>8);
  aOut[1] = (iVal&0xFF);
}

static u16 fts5GetU16(const u8 *aIn){
  return ((u16)aIn[0] << 8) + aIn[1];
}

/*
** The only argument points to a buffer at least 8 bytes in size. This
** function interprets the first 8 bytes of the buffer as a 64-bit big-endian
** unsigned integer and returns the result.
*/
static u64 fts5GetU64(u8 *a){
  return ((u64)a[0] << 56)
       + ((u64)a[1] << 48)
       + ((u64)a[2] << 40)
       + ((u64)a[3] << 32)
       + ((u64)a[4] << 24)
       + ((u64)a[5] << 16)
       + ((u64)a[6] << 8)
       + ((u64)a[7] << 0);
}

/*
** The only argument points to a buffer at least 4 bytes in size. This
** function interprets the first 4 bytes of the buffer as a 32-bit big-endian
** unsigned integer and returns the result.
*/
static u32 fts5GetU32(const u8 *a){
  return ((u32)a[0] << 24)
       + ((u32)a[1] << 16)
       + ((u32)a[2] << 8)
       + ((u32)a[3] << 0);
}

/*
** Write iVal, formated as a 64-bit big-endian unsigned integer, to the
** buffer indicated by the first argument.
*/
static void fts5PutU64(u8 *a, u64 iVal){
  a[0] = ((iVal >> 56) & 0xFF);
  a[1] = ((iVal >> 48) & 0xFF);
  a[2] = ((iVal >> 40) & 0xFF);
  a[3] = ((iVal >> 32) & 0xFF);
  a[4] = ((iVal >> 24) & 0xFF);
  a[5] = ((iVal >> 16) & 0xFF);
  a[6] = ((iVal >>  8) & 0xFF);
  a[7] = ((iVal >>  0) & 0xFF);
}

/*
** Write iVal, formated as a 32-bit big-endian unsigned integer, to the
** buffer indicated by the first argument.
*/
static void fts5PutU32(u8 *a, u32 iVal){
  a[0] = ((iVal >> 24) & 0xFF);
  a[1] = ((iVal >> 16) & 0xFF);
  a[2] = ((iVal >>  8) & 0xFF);
  a[3] = ((iVal >>  0) & 0xFF);
}

/*
** Allocate and return a buffer at least nByte bytes in size.
**
** If an OOM error is encountered, return NULL and set the error code in
** the Fts5Index handle passed as the first argument.
*/

  sqlite3_step(p->pDeleter);
  p->rc = sqlite3_reset(p->pDeleter);
}

/*
** Remove all records associated with segment iSegid.
*/
static void fts5DataRemoveSegment(Fts5Index *p, Fts5StructureSegment *pSeg){
  int iSegid = pSeg->iSegid;
  i64 iFirst = FTS5_SEGMENT_ROWID(iSegid, 0);
  i64 iLast = FTS5_SEGMENT_ROWID(iSegid+1, 0)-1;
  fts5DataDelete(p, iFirst, iLast);

  if( pSeg->nPgTombstone ){
    i64 iTomb1 = FTS5_TOMBSTONE_ROWID(iSegid, 0);
    i64 iTomb2 = FTS5_TOMBSTONE_ROWID(iSegid, pSeg->nPgTombstone-1);
    fts5DataDelete(p, iTomb1, iTomb2);
  }
  if( p->pIdxDeleter==0 ){
    Fts5Config *pConfig = p->pConfig;
    fts5IndexPrepareStmt(p, &p->pIdxDeleter, sqlite3_mprintf(
          "DELETE FROM '%q'.'%q_idx' WHERE segid=?",
          pConfig->zDb, pConfig->zName
    ));
  }

  int rc = SQLITE_OK;
  int i = 0;
  int iLvl;
  int nLevel = 0;
  int nSegment = 0;
  sqlite3_int64 nByte;            /* Bytes of space to allocate at pRet */
  Fts5Structure *pRet = 0;        /* Structure object to return */
  int bStructureV2 = 0;           /* True for FTS5_STRUCTURE_V2 */
  u64 nOriginCntr = 0;            /* Largest origin value seen so far */

  /* Grab the cookie value */
  if( piCookie ) *piCookie = sqlite3Fts5Get32(pData);
  i = 4;

  /* Check if this is a V2 structure record. Set bStructureV2 if it is. */
  if( 0==memcmp(&pData[i], FTS5_STRUCTURE_V2, 4) ){
    i += 4;
    bStructureV2 = 1;
  }

  /* Read the total number of levels and segments from the start of the
  ** structure record.  */
  i += fts5GetVarint32(&pData[i], nLevel);
  i += fts5GetVarint32(&pData[i], nSegment);
  if( nLevel>FTS5_MAX_SEGMENT   || nLevel<0
   || nSegment>FTS5_MAX_SEGMENT || nSegment<0

            rc = FTS5_CORRUPT;
            break;
          }
          assert( pSeg!=0 );
          i += fts5GetVarint32(&pData[i], pSeg->iSegid);
          i += fts5GetVarint32(&pData[i], pSeg->pgnoFirst);
          i += fts5GetVarint32(&pData[i], pSeg->pgnoLast);
          if( bStructureV2 ){
            i += fts5GetVarint(&pData[i], &pSeg->iOrigin1);
            i += fts5GetVarint(&pData[i], &pSeg->iOrigin2);
            i += fts5GetVarint32(&pData[i], pSeg->nPgTombstone);
            i += fts5GetVarint(&pData[i], &pSeg->nEntryTombstone);
            i += fts5GetVarint(&pData[i], &pSeg->nEntry);
            nOriginCntr = MAX(nOriginCntr, pSeg->iOrigin2);
          }
          if( pSeg->pgnoLast<pSeg->pgnoFirst ){
            rc = FTS5_CORRUPT;
            break;
          }
        }
        if( iLvl>0 && pLvl[-1].nMerge && nTotal==0 ) rc = FTS5_CORRUPT;
        if( iLvl==nLevel-1 && pLvl->nMerge ) rc = FTS5_CORRUPT;
      }
    }
    if( nSegment!=0 && rc==SQLITE_OK ) rc = FTS5_CORRUPT;
    if( bStructureV2 ){
      pRet->nOriginCntr = nOriginCntr+1;
    }

    if( rc!=SQLITE_OK ){
      fts5StructureRelease(pRet);
      pRet = 0;
    }
  }

** error has already occurred, this function is a no-op.
*/
static void fts5StructureWrite(Fts5Index *p, Fts5Structure *pStruct){
  if( p->rc==SQLITE_OK ){
    Fts5Buffer buf;               /* Buffer to serialize record into */
    int iLvl;                     /* Used to iterate through levels */
    int iCookie;                  /* Cookie value to store */
    int nHdr = (pStruct->nOriginCntr>0 ? (4+4+9+9+9) : (4+9+9));

    assert( pStruct->nSegment==fts5StructureCountSegments(pStruct) );
    memset(&buf, 0, sizeof(Fts5Buffer));

    /* Append the current configuration cookie */
    iCookie = p->pConfig->iCookie;
    if( iCookie<0 ) iCookie = 0;

    if( 0==sqlite3Fts5BufferSize(&p->rc, &buf, nHdr) ){
      sqlite3Fts5Put32(buf.p, iCookie);
      buf.n = 4;
      if( pStruct->nOriginCntr>0 ){
        fts5BufferSafeAppendBlob(&buf, FTS5_STRUCTURE_V2, 4);
      }
      fts5BufferSafeAppendVarint(&buf, pStruct->nLevel);
      fts5BufferSafeAppendVarint(&buf, pStruct->nSegment);
      fts5BufferSafeAppendVarint(&buf, (i64)pStruct->nWriteCounter);
    }

    for(iLvl=0; iLvl<pStruct->nLevel; iLvl++){
      int iSeg;                     /* Used to iterate through segments */
      Fts5StructureLevel *pLvl = &pStruct->aLevel[iLvl];
      fts5BufferAppendVarint(&p->rc, &buf, pLvl->nMerge);
      fts5BufferAppendVarint(&p->rc, &buf, pLvl->nSeg);
      assert( pLvl->nMerge<=pLvl->nSeg );

      for(iSeg=0; iSeg<pLvl->nSeg; iSeg++){
        Fts5StructureSegment *pSeg = &pLvl->aSeg[iSeg];
        fts5BufferAppendVarint(&p->rc, &buf, pSeg->iSegid);
        fts5BufferAppendVarint(&p->rc, &buf, pSeg->pgnoFirst);
        fts5BufferAppendVarint(&p->rc, &buf, pSeg->pgnoLast);
        if( pStruct->nOriginCntr>0 ){
          fts5BufferAppendVarint(&p->rc, &buf, pSeg->iOrigin1);
          fts5BufferAppendVarint(&p->rc, &buf, pSeg->iOrigin2);
          fts5BufferAppendVarint(&p->rc, &buf, pSeg->nPgTombstone);
          fts5BufferAppendVarint(&p->rc, &buf, pSeg->nEntryTombstone);
          fts5BufferAppendVarint(&p->rc, &buf, pSeg->nEntry);
        }
      }
    }

    fts5DataWrite(p, FTS5_STRUCTURE_ROWID, buf.p, buf.n);
    fts5BufferFree(&buf);
  }
}

    pIter->xNext = fts5SegIterNext_Reverse;
  }else if( p->pConfig->eDetail==FTS5_DETAIL_NONE ){
    pIter->xNext = fts5SegIterNext_None;
  }else{
    pIter->xNext = fts5SegIterNext;
  }
}

/*
** Allocate a tombstone hash page array (pIter->apTombstone) for the
** iterator passed as the second argument. If an OOM error occurs, leave
** an error in the Fts5Index object.
*/
static void fts5SegIterAllocTombstone(Fts5Index *p, Fts5SegIter *pIter){
  const int nTomb = pIter->pSeg->nPgTombstone;
  if( nTomb>0 ){
    Fts5Data **apTomb = 0;
    apTomb = (Fts5Data**)sqlite3Fts5MallocZero(&p->rc, sizeof(Fts5Data)*nTomb);
    if( apTomb ){
      pIter->apTombstone = apTomb;
      pIter->nTombstone = nTomb;
    }
  }
}

/*
** Initialize the iterator object pIter to iterate through the entries in
** segment pSeg. The iterator is left pointing to the first entry when
** this function returns.
**
** If an error occurs, Fts5Index.rc is set to an appropriate error code. If

    pIter->iLeafOffset = 4;
    assert( pIter->pLeaf!=0 );
    assert_nc( pIter->pLeaf->nn>4 );
    assert_nc( fts5LeafFirstTermOff(pIter->pLeaf)==4 );
    pIter->iPgidxOff = pIter->pLeaf->szLeaf+1;
    fts5SegIterLoadTerm(p, pIter, 0);
    fts5SegIterLoadNPos(p, pIter);
    fts5SegIterAllocTombstone(p, pIter);
  }
}

/*
** This function is only ever called on iterators created by calls to
** Fts5IndexQuery() with the FTS5INDEX_QUERY_DESC flag set.
**

      if( flags & FTS5INDEX_QUERY_DESC ){
        fts5SegIterReverse(p, pIter);
      }
    }
  }

  fts5SegIterSetNext(p, pIter);
  fts5SegIterAllocTombstone(p, pIter);

  /* Either:
  **
  **   1) an error has occurred, or
  **   2) the iterator points to EOF, or
  **   3) the iterator points to an entry with term (pTerm/nTerm), or
  **   4) the FTS5INDEX_QUERY_SCAN flag was set and the iterator points

    }else{
      fts5SegIterLoadNPos(p, pIter);
    }
  }

  fts5SegIterSetNext(p, pIter);
}

/*
** Array ap[] contains n elements. Release each of these elements using
** fts5DataRelease(). Then free the array itself using sqlite3_free().
*/
static void fts5IndexFreeArray(Fts5Data **ap, int n){
  if( ap ){
    int ii;
    for(ii=0; ii<n; ii++){
      fts5DataRelease(ap[ii]);
    }
    sqlite3_free(ap);
  }
}

/*
** Zero the iterator passed as the only argument.
*/
static void fts5SegIterClear(Fts5SegIter *pIter){
  fts5BufferFree(&pIter->term);
  fts5DataRelease(pIter->pLeaf);
  fts5DataRelease(pIter->pNextLeaf);
  fts5IndexFreeArray(pIter->apTombstone, pIter->nTombstone);
  fts5DlidxIterFree(pIter->pDlidx);
  sqlite3_free(pIter->aRowidOffset);
  memset(pIter, 0, sizeof(Fts5SegIter));
}

#ifdef SQLITE_DEBUG

** Set the pIter->bEof variable based on the state of the sub-iterators.
*/
static void fts5MultiIterSetEof(Fts5Iter *pIter){
  Fts5SegIter *pSeg = &pIter->aSeg[ pIter->aFirst[1].iFirst ];
  pIter->base.bEof = pSeg->pLeaf==0;
  pIter->iSwitchRowid = pSeg->iRowid;
}

/*
** The argument to this macro must be an Fts5Data structure containing a
** tombstone hash page. This macro returns the key-size of the hash-page.
*/
#define TOMBSTONE_KEYSIZE(pPg) (pPg->p[0]==4 ? 4 : 8)

#define TOMBSTONE_NSLOT(pPg)   \
  ((pPg->nn > 16) ? ((pPg->nn-8) / TOMBSTONE_KEYSIZE(pPg)) : 1)

/*
** Query a single tombstone hash table for rowid iRowid. Return true if
** it is found or false otherwise. The tombstone hash table is one of
** nHashTable tables.
*/
static int fts5IndexTombstoneQuery(
  Fts5Data *pHash,                /* Hash table page to query */
  int nHashTable,                 /* Number of pages attached to segment */
  u64 iRowid                      /* Rowid to query hash for */
){
  const int szKey = TOMBSTONE_KEYSIZE(pHash);
  const int nSlot = TOMBSTONE_NSLOT(pHash);
  int iSlot = (iRowid / nHashTable) % nSlot;
  int nCollide = nSlot;

  if( iRowid==0 ){
    return pHash->p[1];
  }else if( szKey==4 ){
    u32 *aSlot = (u32*)&pHash->p[8];
    while( aSlot[iSlot] ){
      if( fts5GetU32((u8*)&aSlot[iSlot])==iRowid ) return 1;
      if( nCollide--==0 ) break;
      iSlot = (iSlot+1)%nSlot;
    }
  }else{
    u64 *aSlot = (u64*)&pHash->p[8];
    while( aSlot[iSlot] ){
      if( fts5GetU64((u8*)&aSlot[iSlot])==iRowid ) return 1;
      if( nCollide--==0 ) break;
      iSlot = (iSlot+1)%nSlot;
    }
  }

  return 0;
}

/*
** Return true if the iterator passed as the only argument points
** to an segment entry for which there is a tombstone. Return false
** if there is no tombstone or if the iterator is already at EOF.
*/
static int fts5MultiIterIsDeleted(Fts5Iter *pIter){
  int iFirst = pIter->aFirst[1].iFirst;
  Fts5SegIter *pSeg = &pIter->aSeg[iFirst];

  if( pSeg->pLeaf && pSeg->nTombstone ){
    /* Figure out which page the rowid might be present on. */
    int iPg = ((u64)pSeg->iRowid) % pSeg->nTombstone;
    assert( iPg>=0 );

    /* If tombstone hash page iPg has not yet been loaded from the
    ** database, load it now. */
    if( pSeg->apTombstone[iPg]==0 ){
      pSeg->apTombstone[iPg] = fts5DataRead(pIter->pIndex,
          FTS5_TOMBSTONE_ROWID(pSeg->pSeg->iSegid, iPg)
      );
      if( pSeg->apTombstone[iPg]==0 ) return 0;
    }

    return fts5IndexTombstoneQuery(
        pSeg->apTombstone[iPg],
        pSeg->nTombstone,
        pSeg->iRowid
    );
  }

  return 0;
}

/*
** Move the iterator to the next entry.
**
** If an error occurs, an error code is left in Fts5Index.rc. It is not
** considered an error if the iterator reaches EOF, or if it is already at
** EOF when this function is called.

      fts5MultiIterSetEof(pIter);
      pSeg = &pIter->aSeg[pIter->aFirst[1].iFirst];
      if( pSeg->pLeaf==0 ) return;
    }

    fts5AssertMultiIterSetup(p, pIter);
    assert( pSeg==&pIter->aSeg[pIter->aFirst[1].iFirst] && pSeg->pLeaf );
    if( (pIter->bSkipEmpty==0 || pSeg->nPos)
      && 0==fts5MultiIterIsDeleted(pIter)
    ){
      pIter->xSetOutputs(pIter, pSeg);
      return;
    }
    bUseFrom = 0;
  }
}

      ){
        fts5MultiIterAdvanced(p, pIter, iFirst, 1);
        fts5MultiIterSetEof(pIter);
        *pbNewTerm = 1;
      }
      fts5AssertMultiIterSetup(p, pIter);

    }while( (fts5MultiIterIsEmpty(p, pIter) || fts5MultiIterIsDeleted(pIter))
         && (p->rc==SQLITE_OK)
    );
  }
}

static void fts5IterSetOutputs_Noop(Fts5Iter *pUnused1, Fts5SegIter *pUnused2){
  UNUSED_PARAM2(pUnused1, pUnused2);
}

        if( p->rc==SQLITE_OK ) pSeg->xNext(p, pSeg, 0);
        fts5MultiIterAdvanced(p, pNew, iEq, iIter);
      }
    }
    fts5MultiIterSetEof(pNew);
    fts5AssertMultiIterSetup(p, pNew);

    if( (pNew->bSkipEmpty && fts5MultiIterIsEmpty(p, pNew))
     || fts5MultiIterIsDeleted(pNew)
    ){
      fts5MultiIterNext(p, pNew, 0, 0);
    }else if( pNew->base.bEof==0 ){
      Fts5SegIter *pSeg = &pNew->aSeg[pNew->aFirst[1].iFirst];
      pNew->xSetOutputs(pNew, pSeg);
    }

  }else{

** Discard all data currently cached in the hash-tables.
*/
static void fts5IndexDiscardData(Fts5Index *p){
  assert( p->pHash || p->nPendingData==0 );
  if( p->pHash ){
    sqlite3Fts5HashClear(p->pHash);
    p->nPendingData = 0;
    p->nPendingRow = 0;
  }
  p->nContentlessDelete = 0;
}

/*
** Return the size of the prefix, in bytes, that buffer
** (pNew/<length-unknown>) shares with buffer (pOld/nOld).
**
** Buffer (pNew/<length-unknown>) is guaranteed to be greater

    pLvlOut->nSeg++;
    pSeg->pgnoFirst = 1;
    pSeg->iSegid = iSegid;
    pStruct->nSegment++;

    /* Read input from all segments in the input level */
    nInput = pLvl->nSeg;

    /* Set the range of origins that will go into the output segment. */
    if( pStruct->nOriginCntr>0 ){
      pSeg->iOrigin1 = pLvl->aSeg[0].iOrigin1;
      pSeg->iOrigin2 = pLvl->aSeg[pLvl->nSeg-1].iOrigin2;
    }
  }
  bOldest = (pLvlOut->nSeg==1 && pStruct->nLevel==iLvl+2);

  assert( iLvl>=0 );
  for(fts5MultiIterNew(p, pStruct, flags, 0, 0, 0, iLvl, nInput, &pIter);
      fts5MultiIterEof(p, pIter)==0;
      fts5MultiIterNext(p, pIter, 0, 0)

  fts5WriteFinish(p, &writer, &pSeg->pgnoLast);

  assert( pIter!=0 || p->rc!=SQLITE_OK );
  if( fts5MultiIterEof(p, pIter) ){
    int i;

    /* Remove the redundant segments from the %_data table */
    assert( pSeg->nEntry==0 );
    for(i=0; i<nInput; i++){
      Fts5StructureSegment *pOld = &pLvl->aSeg[i];
      pSeg->nEntry += (pOld->nEntry - pOld->nEntryTombstone);
      fts5DataRemoveSegment(p, pOld);
    }

    /* Remove the redundant segments from the input level */
    if( pLvl->nSeg!=nInput ){
      int nMove = (pLvl->nSeg - nInput) * sizeof(Fts5StructureSegment);
      memmove(pLvl->aSeg, &pLvl->aSeg[nInput], nMove);
    }

    pLvl->nMerge = nInput;
  }

  fts5MultiIterFree(pIter);
  fts5BufferFree(&term);
  if( pnRem ) *pnRem -= writer.nLeafWritten;
}

/*
** If this is not a contentless_delete=1 table, or if the 'deletemerge'
** configuration option is set to 0, then this function always returns -1.
** Otherwise, it searches the structure object passed as the second argument
** for a level suitable for merging due to having a large number of
** tombstones in the tombstone hash. If one is found, its index is returned.
** Otherwise, if there is no suitable level, -1.
*/
static int fts5IndexFindDeleteMerge(Fts5Index *p, Fts5Structure *pStruct){
  Fts5Config *pConfig = p->pConfig;
  int iRet = -1;
  if( pConfig->bContentlessDelete && pConfig->nDeleteMerge>0 ){
    int ii;
    int nBest = 0;

    for(ii=0; ii<pStruct->nLevel; ii++){
      Fts5StructureLevel *pLvl = &pStruct->aLevel[ii];
      i64 nEntry = 0;
      i64 nTomb = 0;
      int iSeg;
      for(iSeg=0; iSeg<pLvl->nSeg; iSeg++){
        nEntry += pLvl->aSeg[iSeg].nEntry;
        nTomb += pLvl->aSeg[iSeg].nEntryTombstone;
      }
      assert_nc( nEntry>0 || pLvl->nSeg==0 );
      if( nEntry>0 ){
        int nPercent = (nTomb * 100) / nEntry;
        if( nPercent>=pConfig->nDeleteMerge && nPercent>nBest ){
          iRet = ii;
          nBest = nPercent;
        }
      }
    }
  }
  return iRet;
}

/*
** Do up to nPg pages of automerge work on the index.
**
** Return true if any changes were actually made, or false otherwise.
*/
static int fts5IndexMerge(
  Fts5Index *p,                   /* FTS5 backend object */
  Fts5Structure **ppStruct,       /* IN/OUT: Current structure of index */
  int nPg,                        /* Pages of work to do */
  int nMin                        /* Minimum number of segments to merge */
){
  int nRem = nPg;
  int bRet = 0;
  Fts5Structure *pStruct = *ppStruct;
  while( nRem>0 && p->rc==SQLITE_OK ){
    int iLvl;                   /* To iterate through levels */
    int iBestLvl = 0;           /* Level offering the most input segments */
    int nBest = 0;              /* Number of input segments on best level */

    /* Set iBestLvl to the level to read input segments from. Or to -1 if
    ** there is no level suitable to merge segments from.  */
    assert( pStruct->nLevel>0 );
    for(iLvl=0; iLvl<pStruct->nLevel; iLvl++){
      Fts5StructureLevel *pLvl = &pStruct->aLevel[iLvl];
      if( pLvl->nMerge ){
        if( pLvl->nMerge>nBest ){
          iBestLvl = iLvl;
          nBest = nMin;
        }
        break;
      }
      if( pLvl->nSeg>nBest ){
        nBest = pLvl->nSeg;
        iBestLvl = iLvl;
      }
    }
    if( nBest<nMin ){



      iBestLvl = fts5IndexFindDeleteMerge(p, pStruct);
    }



    if( iBestLvl<0 ) break;

    bRet = 1;
    fts5IndexMergeLevel(p, &pStruct, iBestLvl, &nRem);
    if( p->rc==SQLITE_OK && pStruct->aLevel[iBestLvl].nMerge==0 ){
      fts5StructurePromote(p, iBestLvl+1, pStruct);
    }

    if( nMin==1 ) nMin = 2;
  }
  *ppStruct = pStruct;
  return bRet;
}

/*
** A total of nLeaf leaf pages of data has just been flushed to a level-0

      ** buffer containing the new page footer. Set stack variables aIdx
      ** and nIdx accordingly.  */
      if( pLeaf->nn>pLeaf->szLeaf ){
        int iFirst = 0;
        int i1 = pLeaf->szLeaf;
        int i2 = 0;

        i1 += fts5GetVarint32(&aPg[i1], iFirst);
        if( iFirst<iNext ){
          p->rc = FTS5_CORRUPT;
          break;
        }
        aIdx = sqlite3Fts5MallocZero(&p->rc, (pLeaf->nn-pLeaf->szLeaf)+2);
        if( aIdx==0 ) break;

        i2 = sqlite3Fts5PutVarint(aIdx, iFirst-nShift);
        if( i1<pLeaf->nn ){
          memcpy(&aIdx[i2], &aPg[i1], pLeaf->nn-i1);
          i2 += (pLeaf->nn-i1);
        }
        nIdx = i2;
      }

  Fts5Structure *pStruct;
  int iSegid;
  int pgnoLast = 0;                 /* Last leaf page number in segment */

  /* Obtain a reference to the index structure and allocate a new segment-id
  ** for the new level-0 segment.  */
  pStruct = fts5StructureRead(p);

  fts5StructureInvalidate(p);

  if( sqlite3Fts5HashIsEmpty(pHash)==0 ){
    iSegid = fts5AllocateSegid(p, pStruct);
    if( iSegid ){
      const int pgsz = p->pConfig->pgsz;
      int eDetail = p->pConfig->eDetail;
      int bSecureDelete = p->pConfig->bSecureDelete;
      Fts5StructureSegment *pSeg; /* New segment within pStruct */
      Fts5Buffer *pBuf;           /* Buffer in which to assemble leaf page */
      Fts5Buffer *pPgidx;         /* Buffer in which to assemble pgidx */

      Fts5SegWriter writer;
      fts5WriteInit(p, &writer, iSegid);

      pBuf = &writer.writer.buf;
      pPgidx = &writer.writer.pgidx;

      /* fts5WriteInit() should have initialized the buffers to (most likely)
      ** the maximum space required. */
      assert( p->rc || pBuf->nSpace>=(pgsz + FTS5_DATA_PADDING) );
      assert( p->rc || pPgidx->nSpace>=(pgsz + FTS5_DATA_PADDING) );

      /* Begin scanning through hash table entries. This loop runs once for each
      ** term/doclist currently stored within the hash table. */
      if( p->rc==SQLITE_OK ){
        p->rc = sqlite3Fts5HashScanInit(pHash, 0, 0);
      }
      while( p->rc==SQLITE_OK && 0==sqlite3Fts5HashScanEof(pHash) ){
        const char *zTerm;        /* Buffer containing term */
        int nTerm;                /* Size of zTerm in bytes */
        const u8 *pDoclist;       /* Pointer to doclist for this term */
        int nDoclist;             /* Size of doclist in bytes */

        /* Get the term and doclist for this entry. */
        sqlite3Fts5HashScanEntry(pHash, &zTerm, &pDoclist, &nDoclist);
        nTerm = (int)strlen(zTerm);
        if( bSecureDelete==0 ){
          fts5WriteAppendTerm(p, &writer, nTerm, (const u8*)zTerm);
          if( p->rc!=SQLITE_OK ) break;
          assert( writer.bFirstRowidInPage==0 );
        }

        if( !bSecureDelete && pgsz>=(pBuf->n + pPgidx->n + nDoclist + 1) ){
          /* The entire doclist will fit on the current leaf. */
          fts5BufferSafeAppendBlob(pBuf, pDoclist, nDoclist);
        }else{
          int bTermWritten = !bSecureDelete;
          i64 iRowid = 0;
          i64 iPrev = 0;
          int iOff = 0;

          /* The entire doclist will not fit on this leaf. The following
          ** loop iterates through the poslists that make up the current
          ** doclist.  */
          while( p->rc==SQLITE_OK && iOff<nDoclist ){
            u64 iDelta = 0;
            iOff += fts5GetVarint(&pDoclist[iOff], &iDelta);
            iRowid += iDelta;

            /* If in secure delete mode, and if this entry in the poslist is
            ** in fact a delete, then edit the existing segments directly
            ** using fts5FlushSecureDelete().  */
            if( bSecureDelete ){
              if( eDetail==FTS5_DETAIL_NONE ){
                if( iOff<nDoclist && pDoclist[iOff]==0x00 ){
                  fts5FlushSecureDelete(p, pStruct, zTerm, iRowid);
                  iOff++;
                  if( iOff<nDoclist && pDoclist[iOff]==0x00 ){
                    iOff++;
                    nDoclist = 0;
                  }else{
                    continue;
                  }
                }
              }else if( (pDoclist[iOff] & 0x01) ){
                fts5FlushSecureDelete(p, pStruct, zTerm, iRowid);
                if( p->rc!=SQLITE_OK || pDoclist[iOff]==0x01 ){
                  iOff++;
                  continue;
                }
              }
            }

            if( p->rc==SQLITE_OK && bTermWritten==0 ){
              fts5WriteAppendTerm(p, &writer, nTerm, (const u8*)zTerm);
              bTermWritten = 1;
              assert( p->rc!=SQLITE_OK || writer.bFirstRowidInPage==0 );
            }

            if( writer.bFirstRowidInPage ){
              fts5PutU16(&pBuf->p[0], (u16)pBuf->n);   /* first rowid on page */
              pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], iRowid);
              writer.bFirstRowidInPage = 0;
              fts5WriteDlidxAppend(p, &writer, iRowid);
            }else{
              pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], iRowid-iPrev);
            }
            if( p->rc!=SQLITE_OK ) break;
            assert( pBuf->n<=pBuf->nSpace );
            iPrev = iRowid;

            if( eDetail==FTS5_DETAIL_NONE ){
              if( iOff<nDoclist && pDoclist[iOff]==0 ){
                pBuf->p[pBuf->n++] = 0;
                iOff++;
                if( iOff<nDoclist && pDoclist[iOff]==0 ){
                  pBuf->p[pBuf->n++] = 0;
                  iOff++;
                }
              }
              if( (pBuf->n + pPgidx->n)>=pgsz ){
                fts5WriteFlushLeaf(p, &writer);
              }
            }else{
              int bDummy;
              int nPos;
              int nCopy = fts5GetPoslistSize(&pDoclist[iOff], &nPos, &bDummy);
              nCopy += nPos;
              if( (pBuf->n + pPgidx->n + nCopy) <= pgsz ){
                /* The entire poslist will fit on the current leaf. So copy
                ** it in one go. */
                fts5BufferSafeAppendBlob(pBuf, &pDoclist[iOff], nCopy);
              }else{
                /* The entire poslist will not fit on this leaf. So it needs
                ** to be broken into sections. The only qualification being
                ** that each varint must be stored contiguously.  */
                const u8 *pPoslist = &pDoclist[iOff];
                int iPos = 0;
                while( p->rc==SQLITE_OK ){
                  int nSpace = pgsz - pBuf->n - pPgidx->n;
                  int n = 0;
                  if( (nCopy - iPos)<=nSpace ){
                    n = nCopy - iPos;
                  }else{
                    n = fts5PoslistPrefix(&pPoslist[iPos], nSpace);
                  }
                  assert( n>0 );
                  fts5BufferSafeAppendBlob(pBuf, &pPoslist[iPos], n);
                  iPos += n;
                  if( (pBuf->n + pPgidx->n)>=pgsz ){
                    fts5WriteFlushLeaf(p, &writer);
                  }
                  if( iPos>=nCopy ) break;
                }
              }
              iOff += nCopy;
            }
          }
        }

        /* TODO2: Doclist terminator written here. */
        /* pBuf->p[pBuf->n++] = '\0'; */
        assert( pBuf->n<=pBuf->nSpace );
        if( p->rc==SQLITE_OK ) sqlite3Fts5HashScanNext(pHash);
      }
      sqlite3Fts5HashClear(pHash);
      fts5WriteFinish(p, &writer, &pgnoLast);

      assert( p->rc!=SQLITE_OK || bSecureDelete || pgnoLast>0 );
      if( pgnoLast>0 ){
        /* Update the Fts5Structure. It is written back to the database by the
        ** fts5StructureRelease() call below.  */
        if( pStruct->nLevel==0 ){
          fts5StructureAddLevel(&p->rc, &pStruct);
        }
        fts5StructureExtendLevel(&p->rc, pStruct, 0, 1, 0);
        if( p->rc==SQLITE_OK ){
          pSeg = &pStruct->aLevel[0].aSeg[ pStruct->aLevel[0].nSeg++ ];
          pSeg->iSegid = iSegid;
          pSeg->pgnoFirst = 1;
          pSeg->pgnoLast = pgnoLast;
          if( pStruct->nOriginCntr>0 ){
            pSeg->iOrigin1 = pStruct->nOriginCntr;
            pSeg->iOrigin2 = pStruct->nOriginCntr;
            pSeg->nEntry = p->nPendingRow;
            pStruct->nOriginCntr++;
          }
          pStruct->nSegment++;
        }
        fts5StructurePromote(p, 0, pStruct);
      }
    }
  }

  fts5IndexAutomerge(p, &pStruct, pgnoLast + p->nContentlessDelete);
  fts5IndexCrisismerge(p, &pStruct);
  fts5StructureWrite(p, pStruct);
  fts5StructureRelease(pStruct);
  p->nContentlessDelete = 0;
}

/*
** Flush any data stored in the in-memory hash tables to the database.
*/
static void fts5IndexFlush(Fts5Index *p){
  /* Unless it is empty, flush the hash table to disk */
  if( p->nPendingData || p->nContentlessDelete ){
    assert( p->pHash );

    fts5FlushOneHash(p);
    p->nPendingData = 0;
    p->nPendingRow = 0;
  }
}

static Fts5Structure *fts5IndexOptimizeStruct(
  Fts5Index *p,
  Fts5Structure *pStruct
){
  Fts5Structure *pNew = 0;
  sqlite3_int64 nByte = sizeof(Fts5Structure);
  int nSeg = pStruct->nSegment;
  int i;

  /* Figure out if this structure requires optimization. A structure does
  ** not require optimization if either:
  **
  **  1. it consists of fewer than two segments, or
  **  2. all segments are on the same level, or
  **  3. all segments except one are currently inputs to a merge operation.
  **
  ** In the first case, if there are no tombstone hash pages, return NULL. In
  ** the second, increment the ref-count on *pStruct and return a copy of the
  ** pointer to it.
  */
  if( nSeg==0 ) return 0;
  for(i=0; i<pStruct->nLevel; i++){
    int nThis = pStruct->aLevel[i].nSeg;
    int nMerge = pStruct->aLevel[i].nMerge;
    if( nThis>0 && (nThis==nSeg || (nThis==nSeg-1 && nMerge==nThis)) ){
      if( nSeg==1 && nThis==1 && pStruct->aLevel[i].aSeg[0].nPgTombstone==0 ){
        return 0;
      }
      fts5StructureRef(pStruct);
      return pStruct;
    }
    assert( pStruct->aLevel[i].nMerge<=nThis );
  }

  nByte += (pStruct->nLevel+1) * sizeof(Fts5StructureLevel);
  pNew = (Fts5Structure*)sqlite3Fts5MallocZero(&p->rc, nByte);

  if( pNew ){
    Fts5StructureLevel *pLvl;
    nByte = nSeg * sizeof(Fts5StructureSegment);
    pNew->nLevel = MIN(pStruct->nLevel+1, FTS5_MAX_LEVEL);
    pNew->nRef = 1;
    pNew->nWriteCounter = pStruct->nWriteCounter;
    pNew->nOriginCntr = pStruct->nOriginCntr;
    pLvl = &pNew->aLevel[pNew->nLevel-1];
    pLvl->aSeg = (Fts5StructureSegment*)sqlite3Fts5MallocZero(&p->rc, nByte);
    if( pLvl->aSeg ){
      int iLvl, iSeg;
      int iSegOut = 0;
      /* Iterate through all segments, from oldest to newest. Add them to
      ** the new Fts5Level object so that pLvl->aSeg[0] is the oldest

static int sqlite3Fts5IndexOptimize(Fts5Index *p){
  Fts5Structure *pStruct;
  Fts5Structure *pNew = 0;

  assert( p->rc==SQLITE_OK );
  fts5IndexFlush(p);
  assert( p->nContentlessDelete==0 );
  pStruct = fts5StructureRead(p);
  fts5StructureInvalidate(p);

  if( pStruct ){
    pNew = fts5IndexOptimizeStruct(p, pStruct);
  }
  fts5StructureRelease(pStruct);

}

/*
** This is called to implement the special "VALUES('merge', $nMerge)"
** INSERT command.
*/
static int sqlite3Fts5IndexMerge(Fts5Index *p, int nMerge){
  Fts5Structure *pStruct = 0;

  fts5IndexFlush(p);
  pStruct = fts5StructureRead(p);
  if( pStruct ){
    int nMin = p->pConfig->nUsermerge;
    fts5StructureInvalidate(p);
    if( nMerge<0 ){
      Fts5Structure *pNew = fts5IndexOptimizeStruct(p, pStruct);
      fts5StructureRelease(pStruct);
      pStruct = pNew;
      nMin = 1;
      nMerge = nMerge*-1;
    }
    if( pStruct && pStruct->nLevel ){
      if( fts5IndexMerge(p, &pStruct, nMerge, nMin) ){
        fts5StructureWrite(p, pStruct);
      }
    }

   || (p->nPendingData > p->pConfig->nHashSize)
  ){
    fts5IndexFlush(p);
  }

  p->iWriteRowid = iRowid;
  p->bDelete = bDelete;
  if( bDelete==0 ){
    p->nPendingRow++;
  }
  return fts5IndexReturn(p);
}

/*
** Commit data to disk.
*/
static int sqlite3Fts5IndexSync(Fts5Index *p){

** and the initial version of the "averages" record (a zero-byte blob).
*/
static int sqlite3Fts5IndexReinit(Fts5Index *p){
  Fts5Structure s;
  fts5StructureInvalidate(p);
  fts5IndexDiscardData(p);
  memset(&s, 0, sizeof(Fts5Structure));
  if( p->pConfig->bContentlessDelete ){
    s.nOriginCntr = 1;
  }
  fts5DataWrite(p, FTS5_AVERAGES_ROWID, (const u8*)"", 0);
  fts5StructureWrite(p, &s);
  return fts5IndexReturn(p);
}

/*
** Open a new Fts5Index handle. If the bCreate argument is true, create

static int sqlite3Fts5IndexLoadConfig(Fts5Index *p){
  Fts5Structure *pStruct;
  pStruct = fts5StructureRead(p);
  fts5StructureRelease(pStruct);
  return fts5IndexReturn(p);
}

/*
** Retrieve the origin value that will be used for the segment currently
** being accumulated in the in-memory hash table when it is flushed to
** disk. If successful, SQLITE_OK is returned and (*piOrigin) set to
** the queried value. Or, if an error occurs, an error code is returned
** and the final value of (*piOrigin) is undefined.
*/
static int sqlite3Fts5IndexGetOrigin(Fts5Index *p, i64 *piOrigin){
  Fts5Structure *pStruct;
  pStruct = fts5StructureRead(p);
  if( pStruct ){
    *piOrigin = pStruct->nOriginCntr;
    fts5StructureRelease(pStruct);
  }
  return fts5IndexReturn(p);
}

/*
** Buffer pPg contains a page of a tombstone hash table - one of nPg pages
** associated with the same segment. This function adds rowid iRowid to
** the hash table. The caller is required to guarantee that there is at
** least one free slot on the page.
**
** If parameter bForce is false and the hash table is deemed to be full
** (more than half of the slots are occupied), then non-zero is returned
** and iRowid not inserted. Or, if bForce is true or if the hash table page
** is not full, iRowid is inserted and zero returned.
*/
static int fts5IndexTombstoneAddToPage(
  Fts5Data *pPg,
  int bForce,
  int nPg,
  u64 iRowid
){
  const int szKey = TOMBSTONE_KEYSIZE(pPg);
  const int nSlot = TOMBSTONE_NSLOT(pPg);
  const int nElem = fts5GetU32(&pPg->p[4]);
  int iSlot = (iRowid / nPg) % nSlot;
  int nCollide = nSlot;

  if( szKey==4 && iRowid>0xFFFFFFFF ) return 2;
  if( iRowid==0 ){
    pPg->p[1] = 0x01;
    return 0;
  }

  if( bForce==0 && nElem>=(nSlot/2) ){
    return 1;
  }

  fts5PutU32(&pPg->p[4], nElem+1);
  if( szKey==4 ){
    u32 *aSlot = (u32*)&pPg->p[8];
    while( aSlot[iSlot] ){
      iSlot = (iSlot + 1) % nSlot;
      if( nCollide--==0 ) return 0;
    }
    fts5PutU32((u8*)&aSlot[iSlot], (u32)iRowid);
  }else{
    u64 *aSlot = (u64*)&pPg->p[8];
    while( aSlot[iSlot] ){
      iSlot = (iSlot + 1) % nSlot;
      if( nCollide--==0 ) return 0;
    }
    fts5PutU64((u8*)&aSlot[iSlot], iRowid);
  }

  return 0;
}

/*
** This function attempts to build a new hash containing all the keys
** currently in the tombstone hash table for segment pSeg. The new
** hash will be stored in the nOut buffers passed in array apOut[].
** All pages of the new hash use key-size szKey (4 or 8).
**
** Return 0 if the hash is successfully rebuilt into the nOut pages.
** Or non-zero if it is not (because one page became overfull). In this
** case the caller should retry with a larger nOut parameter.
**
** Parameter pData1 is page iPg1 of the hash table being rebuilt.
*/
static int fts5IndexTombstoneRehash(
  Fts5Index *p,
  Fts5StructureSegment *pSeg,     /* Segment to rebuild hash of */
  Fts5Data *pData1,               /* One page of current hash - or NULL */
  int iPg1,                       /* Which page of the current hash is pData1 */
  int szKey,                      /* 4 or 8, the keysize */
  int nOut,                       /* Number of output pages */
  Fts5Data **apOut                /* Array of output hash pages */
){
  int ii;
  int res = 0;

  /* Initialize the headers of all the output pages */
  for(ii=0; ii<nOut; ii++){
    apOut[ii]->p[0] = szKey;
    fts5PutU32(&apOut[ii]->p[4], 0);
  }

  /* Loop through the current pages of the hash table. */
  for(ii=0; res==0 && ii<pSeg->nPgTombstone; ii++){
    Fts5Data *pData = 0;          /* Page ii of the current hash table */
    Fts5Data *pFree = 0;          /* Free this at the end of the loop */

    if( iPg1==ii ){
      pData = pData1;
    }else{
      pFree = pData = fts5DataRead(p, FTS5_TOMBSTONE_ROWID(pSeg->iSegid, ii));
    }

    if( pData ){
      int szKeyIn = TOMBSTONE_KEYSIZE(pData);
      int nSlotIn = (pData->nn - 8) / szKeyIn;
      int iIn;
      for(iIn=0; iIn<nSlotIn; iIn++){
        u64 iVal = 0;

        /* Read the value from slot iIn of the input page into iVal. */
        if( szKeyIn==4 ){
          u32 *aSlot = (u32*)&pData->p[8];
          if( aSlot[iIn] ) iVal = fts5GetU32((u8*)&aSlot[iIn]);
        }else{
          u64 *aSlot = (u64*)&pData->p[8];
          if( aSlot[iIn] ) iVal = fts5GetU64((u8*)&aSlot[iIn]);
        }

        /* If iVal is not 0 at this point, insert it into the new hash table */
        if( iVal ){
          Fts5Data *pPg = apOut[(iVal % nOut)];
          res = fts5IndexTombstoneAddToPage(pPg, 0, nOut, iVal);
          if( res ) break;
        }
      }

      /* If this is page 0 of the old hash, copy the rowid-0-flag from the
      ** old hash to the new.  */
      if( ii==0 ){
        apOut[0]->p[1] = pData->p[1];
      }
    }
    fts5DataRelease(pFree);
  }

  return res;
}

/*
** This is called to rebuild the hash table belonging to segment pSeg.
** If parameter pData1 is not NULL, then one page of the existing hash table
** has already been loaded - pData1, which is page iPg1. The key-size for
** the new hash table is szKey (4 or 8).
**
** If successful, the new hash table is not written to disk. Instead,
** output parameter (*pnOut) is set to the number of pages in the new
** hash table, and (*papOut) to point to an array of buffers containing
** the new page data.
**
** If an error occurs, an error code is left in the Fts5Index object and
** both output parameters set to 0 before returning.
*/
static void fts5IndexTombstoneRebuild(
  Fts5Index *p,
  Fts5StructureSegment *pSeg,     /* Segment to rebuild hash of */
  Fts5Data *pData1,               /* One page of current hash - or NULL */
  int iPg1,                       /* Which page of the current hash is pData1 */
  int szKey,                      /* 4 or 8, the keysize */
  int *pnOut,                     /* OUT: Number of output pages */
  Fts5Data ***papOut              /* OUT: Output hash pages */
){
  const int MINSLOT = 32;
  int nSlotPerPage = MAX(MINSLOT, (p->pConfig->pgsz - 8) / szKey);
  int nSlot = 0;                  /* Number of slots in each output page */
  int nOut = 0;

  /* Figure out how many output pages (nOut) and how many slots per
  ** page (nSlot).  There are three possibilities:
  **
  **   1. The hash table does not yet exist. In this case the new hash
  **      table will consist of a single page with MINSLOT slots.
  **
  **   2. The hash table exists but is currently a single page. In this
  **      case an attempt is made to grow the page to accommodate the new
  **      entry. The page is allowed to grow up to nSlotPerPage (see above)
  **      slots.
  **
  **   3. The hash table already consists of more than one page, or of
  **      a single page already so large that it cannot be grown. In this
  **      case the new hash consists of (nPg*2+1) pages of nSlotPerPage
  **      slots each, where nPg is the current number of pages in the
  **      hash table.
  */
  if( pSeg->nPgTombstone==0 ){
    /* Case 1. */
    nOut = 1;
    nSlot = MINSLOT;
  }else if( pSeg->nPgTombstone==1 ){
    /* Case 2. */
    int nElem = (int)fts5GetU32(&pData1->p[4]);
    assert( pData1 && iPg1==0 );
    nOut = 1;
    nSlot = MAX(nElem*4, MINSLOT);
    if( nSlot>nSlotPerPage ) nOut = 0;
  }
  if( nOut==0 ){
    /* Case 3. */
    nOut = (pSeg->nPgTombstone * 2 + 1);
    nSlot = nSlotPerPage;
  }

  /* Allocate the required array and output pages */
  while( 1 ){
    int res = 0;
    int ii = 0;
    int szPage = 0;
    Fts5Data **apOut = 0;

    /* Allocate space for the new hash table */
    assert( nSlot>=MINSLOT );
    apOut = (Fts5Data**)sqlite3Fts5MallocZero(&p->rc, sizeof(Fts5Data*) * nOut);
    szPage = 8 + nSlot*szKey;
    for(ii=0; ii<nOut; ii++){
      Fts5Data *pNew = (Fts5Data*)sqlite3Fts5MallocZero(&p->rc,
          sizeof(Fts5Data)+szPage
      );
      if( pNew ){
        pNew->nn = szPage;
        pNew->p = (u8*)&pNew[1];
        apOut[ii] = pNew;
      }
    }

    /* Rebuild the hash table. */
    if( p->rc==SQLITE_OK ){
      res = fts5IndexTombstoneRehash(p, pSeg, pData1, iPg1, szKey, nOut, apOut);
    }
    if( res==0 ){
      if( p->rc ){
        fts5IndexFreeArray(apOut, nOut);
        apOut = 0;
        nOut = 0;
      }
      *pnOut = nOut;
      *papOut = apOut;
      break;
    }

    /* If control flows to here, it was not possible to rebuild the hash
    ** table. Free all buffers and then try again with more pages. */
    assert( p->rc==SQLITE_OK );
    fts5IndexFreeArray(apOut, nOut);
    nSlot = nSlotPerPage;
    nOut = nOut*2 + 1;
  }
}


/*
** Add a tombstone for rowid iRowid to segment pSeg.
*/
static void fts5IndexTombstoneAdd(
  Fts5Index *p,
  Fts5StructureSegment *pSeg,
  u64 iRowid
){
  Fts5Data *pPg = 0;
  int iPg = -1;
  int szKey = 0;
  int nHash = 0;
  Fts5Data **apHash = 0;

  p->nContentlessDelete++;

  if( pSeg->nPgTombstone>0 ){
    iPg = iRowid % pSeg->nPgTombstone;
    pPg = fts5DataRead(p, FTS5_TOMBSTONE_ROWID(pSeg->iSegid,iPg));
    if( pPg==0 ){
      assert( p->rc!=SQLITE_OK );
      return;
    }

    if( 0==fts5IndexTombstoneAddToPage(pPg, 0, pSeg->nPgTombstone, iRowid) ){
      fts5DataWrite(p, FTS5_TOMBSTONE_ROWID(pSeg->iSegid,iPg), pPg->p, pPg->nn);
      fts5DataRelease(pPg);
      return;
    }
  }

  /* Have to rebuild the hash table. First figure out the key-size (4 or 8). */
  szKey = pPg ? TOMBSTONE_KEYSIZE(pPg) : 4;
  if( iRowid>0xFFFFFFFF ) szKey = 8;

  /* Rebuild the hash table */
  fts5IndexTombstoneRebuild(p, pSeg, pPg, iPg, szKey, &nHash, &apHash);
  assert( p->rc==SQLITE_OK || (nHash==0 && apHash==0) );

  /* If all has succeeded, write the new rowid into one of the new hash
  ** table pages, then write them all out to disk. */
  if( nHash ){
    int ii = 0;
    fts5IndexTombstoneAddToPage(apHash[iRowid % nHash], 1, nHash, iRowid);
    for(ii=0; ii<nHash; ii++){
      i64 iTombstoneRowid = FTS5_TOMBSTONE_ROWID(pSeg->iSegid, ii);
      fts5DataWrite(p, iTombstoneRowid, apHash[ii]->p, apHash[ii]->nn);
    }
    pSeg->nPgTombstone = nHash;
    fts5StructureWrite(p, p->pStruct);
  }

  fts5DataRelease(pPg);
  fts5IndexFreeArray(apHash, nHash);
}

/*
** Add iRowid to the tombstone list of the segment or segments that contain
** rows from origin iOrigin. Return SQLITE_OK if successful, or an SQLite
** error code otherwise.
*/
static int sqlite3Fts5IndexContentlessDelete(Fts5Index *p, i64 iOrigin, i64 iRowid){
  Fts5Structure *pStruct;
  pStruct = fts5StructureRead(p);
  if( pStruct ){
    int bFound = 0;               /* True after pSeg->nEntryTombstone incr. */
    int iLvl;
    for(iLvl=pStruct->nLevel-1; iLvl>=0; iLvl--){
      int iSeg;
      for(iSeg=pStruct->aLevel[iLvl].nSeg-1; iSeg>=0; iSeg--){
        Fts5StructureSegment *pSeg = &pStruct->aLevel[iLvl].aSeg[iSeg];
        if( pSeg->iOrigin1<=(u64)iOrigin && pSeg->iOrigin2>=(u64)iOrigin ){
          if( bFound==0 ){
            pSeg->nEntryTombstone++;
            bFound = 1;
          }
          fts5IndexTombstoneAdd(p, pSeg, iRowid);
        }
      }
    }
    fts5StructureRelease(pStruct);
  }
  return fts5IndexReturn(p);
}

/*************************************************************************
**************************************************************************
** Below this point is the implementation of the integrity-check
** functionality.
*/

/*************************************************************************
**************************************************************************
** Below this point is the implementation of the fts5_decode() scalar
** function only.
*/

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
/*
** Decode a segment-data rowid from the %_data table. This function is
** the opposite of macro FTS5_SEGMENT_ROWID().
*/
static void fts5DecodeRowid(
  i64 iRowid,                     /* Rowid from %_data table */
  int *pbTombstone,               /* OUT: Tombstone hash flag */
  int *piSegid,                   /* OUT: Segment id */
  int *pbDlidx,                   /* OUT: Dlidx flag */
  int *piHeight,                  /* OUT: Height */
  int *piPgno                     /* OUT: Page number */
){
  *piPgno = (int)(iRowid & (((i64)1 << FTS5_DATA_PAGE_B) - 1));
  iRowid >>= FTS5_DATA_PAGE_B;

  *piHeight = (int)(iRowid & (((i64)1 << FTS5_DATA_HEIGHT_B) - 1));
  iRowid >>= FTS5_DATA_HEIGHT_B;

  *pbDlidx = (int)(iRowid & 0x0001);
  iRowid >>= FTS5_DATA_DLI_B;

  *piSegid = (int)(iRowid & (((i64)1 << FTS5_DATA_ID_B) - 1));
  iRowid >>= FTS5_DATA_ID_B;

  *pbTombstone = (int)(iRowid & 0x0001);
}
#endif /* SQLITE_TEST || SQLITE_FTS5_DEBUG */

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
static void fts5DebugRowid(int *pRc, Fts5Buffer *pBuf, i64 iKey){
  int iSegid, iHeight, iPgno, bDlidx, bTomb;     /* Rowid compenents */
  fts5DecodeRowid(iKey, &bTomb, &iSegid, &bDlidx, &iHeight, &iPgno);

  if( iSegid==0 ){
    if( iKey==FTS5_AVERAGES_ROWID ){
      sqlite3Fts5BufferAppendPrintf(pRc, pBuf, "{averages} ");
    }else{
      sqlite3Fts5BufferAppendPrintf(pRc, pBuf, "{structure}");
    }
  }
  else{
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, "{%s%ssegid=%d h=%d pgno=%d}",
        bDlidx ? "dlidx " : "",
        bTomb ? "tombstone " : "",
        iSegid, iHeight, iPgno
    );
  }
}
#endif /* SQLITE_TEST || SQLITE_FTS5_DEBUG */

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
static void fts5DebugStructure(
  int *pRc,                       /* IN/OUT: error code */
  Fts5Buffer *pBuf,
  Fts5Structure *p
){
  int iLvl, iSeg;                 /* Iterate through levels, segments */

  for(iLvl=0; iLvl<p->nLevel; iLvl++){
    Fts5StructureLevel *pLvl = &p->aLevel[iLvl];
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf,
        " {lvl=%d nMerge=%d nSeg=%d", iLvl, pLvl->nMerge, pLvl->nSeg
    );
    for(iSeg=0; iSeg<pLvl->nSeg; iSeg++){
      Fts5StructureSegment *pSeg = &pLvl->aSeg[iSeg];
      sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " {id=%d leaves=%d..%d",
          pSeg->iSegid, pSeg->pgnoFirst, pSeg->pgnoLast
      );
      if( pSeg->iOrigin1>0 ){
        sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " origin=%lld..%lld",
            pSeg->iOrigin1, pSeg->iOrigin2
        );
      }
      sqlite3Fts5BufferAppendPrintf(pRc, pBuf, "}");
    }
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, "}");
  }
}
#endif /* SQLITE_TEST || SQLITE_FTS5_DEBUG */

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
/*
** This is part of the fts5_decode() debugging aid.
**
** Arguments pBlob/nBlob contain a serialized Fts5Structure object. This
** function appends a human-readable representation of the same object
** to the buffer passed as the second argument.
*/

    *pRc = rc;
    return;
  }

  fts5DebugStructure(pRc, pBuf, p);
  fts5StructureRelease(p);
}
#endif /* SQLITE_TEST || SQLITE_FTS5_DEBUG */

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
/*
** This is part of the fts5_decode() debugging aid.
**
** Arguments pBlob/nBlob contain an "averages" record. This function
** appends a human-readable representation of record to the buffer passed
** as the second argument.
*/

  while( i<nBlob ){
    u64 iVal;
    i += sqlite3Fts5GetVarint(&pBlob[i], &iVal);
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, "%s%d", zSpace, (int)iVal);
    zSpace = " ";
  }
}
#endif /* SQLITE_TEST || SQLITE_FTS5_DEBUG */

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
/*
** Buffer (a/n) is assumed to contain a list of serialized varints. Read
** each varint and append its string representation to buffer pBuf. Return
** after either the input buffer is exhausted or a 0 value is read.
**
** The return value is the number of bytes read from the input buffer.
*/
static int fts5DecodePoslist(int *pRc, Fts5Buffer *pBuf, const u8 *a, int n){
  int iOff = 0;
  while( iOff<n ){
    int iVal;
    iOff += fts5GetVarint32(&a[iOff], iVal);
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " %d", iVal);
  }
  return iOff;
}
#endif /* SQLITE_TEST || SQLITE_FTS5_DEBUG */

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
/*
** The start of buffer (a/n) contains the start of a doclist. The doclist
** may or may not finish within the buffer. This function appends a text
** representation of the part of the doclist that is present to buffer
** pBuf.
**
** The return value is the number of bytes read from the input buffer.

      iDocid += iDelta;
      sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " id=%lld", iDocid);
    }
  }

  return iOff;
}
#endif /* SQLITE_TEST || SQLITE_FTS5_DEBUG */

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
/*
** This function is part of the fts5_decode() debugging function. It is
** only ever used with detail=none tables.
**
** Buffer (pData/nData) contains a doclist in the format used by detail=none
** tables. This function appends a human-readable version of that list to
** buffer pBuf.

        zApp = "*";
      }
    }

    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " %lld%s", iRowid, zApp);
  }
}
#endif /* SQLITE_TEST || SQLITE_FTS5_DEBUG */

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
/*
** The implementation of user-defined scalar function fts5_decode().
*/
static void fts5DecodeFunction(
  sqlite3_context *pCtx,          /* Function call context */
  int nArg,                       /* Number of args (always 2) */
  sqlite3_value **apVal           /* Function arguments */
){
  i64 iRowid;                     /* Rowid for record being decoded */
  int iSegid,iHeight,iPgno,bDlidx;/* Rowid components */
  int bTomb;
  const u8 *aBlob; int n;         /* Record to decode */
  u8 *a = 0;
  Fts5Buffer s;                   /* Build up text to return here */
  int rc = SQLITE_OK;             /* Return code */
  sqlite3_int64 nSpace = 0;
  int eDetailNone = (sqlite3_user_data(pCtx)!=0);

  n = sqlite3_value_bytes(apVal[1]);
  aBlob = sqlite3_value_blob(apVal[1]);
  nSpace = n + FTS5_DATA_ZERO_PADDING;
  a = (u8*)sqlite3Fts5MallocZero(&rc, nSpace);
  if( a==0 ) goto decode_out;
  if( n>0 ) memcpy(a, aBlob, n);

  fts5DecodeRowid(iRowid, &bTomb, &iSegid, &bDlidx, &iHeight, &iPgno);

  fts5DebugRowid(&rc, &s, iRowid);
  if( bDlidx ){
    Fts5Data dlidx;
    Fts5DlidxLvl lvl;

    dlidx.p = a;
    dlidx.nn = n;

    memset(&lvl, 0, sizeof(Fts5DlidxLvl));
    lvl.pData = &dlidx;
    lvl.iLeafPgno = iPgno;

    for(fts5DlidxLvlNext(&lvl); lvl.bEof==0; fts5DlidxLvlNext(&lvl)){
      sqlite3Fts5BufferAppendPrintf(&rc, &s,
          " %d(%lld)", lvl.iLeafPgno, lvl.iRowid
      );
    }
  }else if( bTomb ){
    u32 nElem  = fts5GetU32(&a[4]);
    int szKey = (aBlob[0]==4 || aBlob[0]==8) ? aBlob[0] : 8;
    int nSlot = (n - 8) / szKey;
    int ii;
    sqlite3Fts5BufferAppendPrintf(&rc, &s, " nElem=%d", (int)nElem);
    if( aBlob[1] ){
      sqlite3Fts5BufferAppendPrintf(&rc, &s, " 0");
    }
    for(ii=0; ii<nSlot; ii++){
      u64 iVal = 0;
      if( szKey==4 ){
        u32 *aSlot = (u32*)&aBlob[8];
        if( aSlot[ii] ) iVal = fts5GetU32((u8*)&aSlot[ii]);
      }else{
        u64 *aSlot = (u64*)&aBlob[8];
        if( aSlot[ii] ) iVal = fts5GetU64((u8*)&aSlot[ii]);
      }
      if( iVal!=0 ){
        sqlite3Fts5BufferAppendPrintf(&rc, &s, " %lld", (i64)iVal);
      }
    }
  }else if( iSegid==0 ){
    if( iRowid==FTS5_AVERAGES_ROWID ){
      fts5DecodeAverages(&rc, &s, a, n);
    }else{
      fts5DecodeStructure(&rc, &s, a, n);
    }

  if( rc==SQLITE_OK ){
    sqlite3_result_text(pCtx, (const char*)s.p, s.n, SQLITE_TRANSIENT);
  }else{
    sqlite3_result_error_code(pCtx, rc);
  }
  fts5BufferFree(&s);
}
#endif /* SQLITE_TEST || SQLITE_FTS5_DEBUG */

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
/*
** The implementation of user-defined scalar function fts5_rowid().
*/
static void fts5RowidFunction(
  sqlite3_context *pCtx,          /* Function call context */
  int nArg,                       /* Number of args (always 2) */
  sqlite3_value **apVal           /* Function arguments */

    }else{
      sqlite3_result_error(pCtx,
        "first arg to fts5_rowid() must be 'segment'" , -1
      );
    }
  }
}
#endif /* SQLITE_TEST || SQLITE_FTS5_DEBUG */

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)

typedef struct Fts5StructVtab Fts5StructVtab;
struct Fts5StructVtab {
  sqlite3_vtab base;
};

typedef struct Fts5StructVcsr Fts5StructVcsr;
struct Fts5StructVcsr {
  sqlite3_vtab_cursor base;
  Fts5Structure *pStruct;
  int iLevel;
  int iSeg;
  int iRowid;
};

/*
** Create a new fts5_structure() table-valued function.
*/
static int fts5structConnectMethod(
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  Fts5StructVtab *pNew = 0;
  int rc = SQLITE_OK;

  rc = sqlite3_declare_vtab(db,
      "CREATE TABLE xyz("
          "level, segment, merge, segid, leaf1, leaf2, loc1, loc2, "
          "npgtombstone, nentrytombstone, nentry, struct HIDDEN);"
  );
  if( rc==SQLITE_OK ){
    pNew = sqlite3Fts5MallocZero(&rc, sizeof(*pNew));
  }

  *ppVtab = (sqlite3_vtab*)pNew;
  return rc;
}

/*
** We must have a single struct=? constraint that will be passed through
** into the xFilter method.  If there is no valid stmt=? constraint,
** then return an SQLITE_CONSTRAINT error.
*/
static int fts5structBestIndexMethod(
  sqlite3_vtab *tab,
  sqlite3_index_info *pIdxInfo
){
  int i;
  int rc = SQLITE_CONSTRAINT;
  struct sqlite3_index_constraint *p;
  pIdxInfo->estimatedCost = (double)100;
  pIdxInfo->estimatedRows = 100;
  pIdxInfo->idxNum = 0;
  for(i=0, p=pIdxInfo->aConstraint; i<pIdxInfo->nConstraint; i++, p++){
    if( p->usable==0 ) continue;
    if( p->op==SQLITE_INDEX_CONSTRAINT_EQ && p->iColumn==11 ){
      rc = SQLITE_OK;
      pIdxInfo->aConstraintUsage[i].omit = 1;
      pIdxInfo->aConstraintUsage[i].argvIndex = 1;
      break;
    }
  }
  return rc;
}

/*
** This method is the destructor for bytecodevtab objects.
*/
static int fts5structDisconnectMethod(sqlite3_vtab *pVtab){
  Fts5StructVtab *p = (Fts5StructVtab*)pVtab;
  sqlite3_free(p);
  return SQLITE_OK;
}

/*
** Constructor for a new bytecodevtab_cursor object.
*/
static int fts5structOpenMethod(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCsr){
  int rc = SQLITE_OK;
  Fts5StructVcsr *pNew = 0;

  pNew = sqlite3Fts5MallocZero(&rc, sizeof(*pNew));
  *ppCsr = (sqlite3_vtab_cursor*)pNew;

  return SQLITE_OK;
}

/*
** Destructor for a bytecodevtab_cursor.
*/
static int fts5structCloseMethod(sqlite3_vtab_cursor *cur){
  Fts5StructVcsr *pCsr = (Fts5StructVcsr*)cur;
  fts5StructureRelease(pCsr->pStruct);
  sqlite3_free(pCsr);
  return SQLITE_OK;
}


/*
** Advance a bytecodevtab_cursor to its next row of output.
*/
static int fts5structNextMethod(sqlite3_vtab_cursor *cur){
  Fts5StructVcsr *pCsr = (Fts5StructVcsr*)cur;
  Fts5Structure *p = pCsr->pStruct;

  assert( pCsr->pStruct );
  pCsr->iSeg++;
  pCsr->iRowid++;
  while( pCsr->iLevel<p->nLevel && pCsr->iSeg>=p->aLevel[pCsr->iLevel].nSeg ){
    pCsr->iLevel++;
    pCsr->iSeg = 0;
  }
  if( pCsr->iLevel>=p->nLevel ){
    fts5StructureRelease(pCsr->pStruct);
    pCsr->pStruct = 0;
  }
  return SQLITE_OK;
}

/*
** Return TRUE if the cursor has been moved off of the last
** row of output.
*/
static int fts5structEofMethod(sqlite3_vtab_cursor *cur){
  Fts5StructVcsr *pCsr = (Fts5StructVcsr*)cur;
  return pCsr->pStruct==0;
}

static int fts5structRowidMethod(
  sqlite3_vtab_cursor *cur,
  sqlite_int64 *piRowid
){
  Fts5StructVcsr *pCsr = (Fts5StructVcsr*)cur;
  *piRowid = pCsr->iRowid;
  return SQLITE_OK;
}

/*
** Return values of columns for the row at which the bytecodevtab_cursor
** is currently pointing.
*/
static int fts5structColumnMethod(
  sqlite3_vtab_cursor *cur,   /* The cursor */
  sqlite3_context *ctx,       /* First argument to sqlite3_result_...() */
  int i                       /* Which column to return */
){
  Fts5StructVcsr *pCsr = (Fts5StructVcsr*)cur;
  Fts5Structure *p = pCsr->pStruct;
  Fts5StructureSegment *pSeg = &p->aLevel[pCsr->iLevel].aSeg[pCsr->iSeg];

  switch( i ){
    case 0: /* level */
      sqlite3_result_int(ctx, pCsr->iLevel);
      break;
    case 1: /* segment */
      sqlite3_result_int(ctx, pCsr->iSeg);
      break;
    case 2: /* merge */
      sqlite3_result_int(ctx, pCsr->iSeg < p->aLevel[pCsr->iLevel].nMerge);
      break;
    case 3: /* segid */
      sqlite3_result_int(ctx, pSeg->iSegid);
      break;
    case 4: /* leaf1 */
      sqlite3_result_int(ctx, pSeg->pgnoFirst);
      break;
    case 5: /* leaf2 */
      sqlite3_result_int(ctx, pSeg->pgnoLast);
      break;
    case 6: /* origin1 */
      sqlite3_result_int64(ctx, pSeg->iOrigin1);
      break;
    case 7: /* origin2 */
      sqlite3_result_int64(ctx, pSeg->iOrigin2);
      break;
    case 8: /* npgtombstone */
      sqlite3_result_int(ctx, pSeg->nPgTombstone);
      break;
    case 9: /* nentrytombstone */
      sqlite3_result_int64(ctx, pSeg->nEntryTombstone);
      break;
    case 10: /* nentry */
      sqlite3_result_int64(ctx, pSeg->nEntry);
      break;
  }
  return SQLITE_OK;
}

/*
** Initialize a cursor.
**
**    idxNum==0     means show all subprograms
**    idxNum==1     means show only the main bytecode and omit subprograms.
*/
static int fts5structFilterMethod(
  sqlite3_vtab_cursor *pVtabCursor,
  int idxNum, const char *idxStr,
  int argc, sqlite3_value **argv
){
  Fts5StructVcsr *pCsr = (Fts5StructVcsr *)pVtabCursor;
  int rc = SQLITE_OK;

  const u8 *aBlob = 0;
  int nBlob = 0;

  assert( argc==1 );
  fts5StructureRelease(pCsr->pStruct);
  pCsr->pStruct = 0;

  nBlob = sqlite3_value_bytes(argv[0]);
  aBlob = (const u8*)sqlite3_value_blob(argv[0]);
  rc = fts5StructureDecode(aBlob, nBlob, 0, &pCsr->pStruct);
  if( rc==SQLITE_OK ){
    pCsr->iLevel = 0;
    pCsr->iRowid = 0;
    pCsr->iSeg = -1;
    rc = fts5structNextMethod(pVtabCursor);
  }

  return rc;
}

#endif /* SQLITE_TEST || SQLITE_FTS5_DEBUG */

/*
** This is called as part of registering the FTS5 module with database
** connection db. It registers several user-defined scalar functions useful
** with FTS5.
**
** If successful, SQLITE_OK is returned. If an error occurs, some other
** SQLite error code is returned instead.
*/
static int sqlite3Fts5IndexInit(sqlite3 *db){
#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
  int rc = sqlite3_create_function(
      db, "fts5_decode", 2, SQLITE_UTF8, 0, fts5DecodeFunction, 0, 0
  );

  if( rc==SQLITE_OK ){
    rc = sqlite3_create_function(
        db, "fts5_decode_none", 2,
        SQLITE_UTF8, (void*)db, fts5DecodeFunction, 0, 0
    );
  }

  if( rc==SQLITE_OK ){
    rc = sqlite3_create_function(
        db, "fts5_rowid", -1, SQLITE_UTF8, 0, fts5RowidFunction, 0, 0
    );
  }

  if( rc==SQLITE_OK ){
    static const sqlite3_module fts5structure_module = {
      0,                           /* iVersion      */
      0,                           /* xCreate       */
      fts5structConnectMethod,     /* xConnect      */
      fts5structBestIndexMethod,   /* xBestIndex    */
      fts5structDisconnectMethod,  /* xDisconnect   */
      0,                           /* xDestroy      */
      fts5structOpenMethod,        /* xOpen         */
      fts5structCloseMethod,       /* xClose        */
      fts5structFilterMethod,      /* xFilter       */
      fts5structNextMethod,        /* xNext         */
      fts5structEofMethod,         /* xEof          */
      fts5structColumnMethod,      /* xColumn       */
      fts5structRowidMethod,       /* xRowid        */
      0,                           /* xUpdate       */
      0,                           /* xBegin        */
      0,                           /* xSync         */
      0,                           /* xCommit       */
      0,                           /* xRollback     */
      0,                           /* xFindFunction */
      0,                           /* xRename       */
      0,                           /* xSavepoint    */
      0,                           /* xRelease      */
      0,                           /* xRollbackTo   */
      0                            /* xShadowName   */
    };
    rc = sqlite3_create_module(db, "fts5_structure", &fts5structure_module, 0);
  }
  return rc;
#else
  return SQLITE_OK;
  UNUSED_PARAM(db);
#endif
}

){
  Fts5FullTable *pTab = (Fts5FullTable*)pVtab;
  Fts5Config *pConfig = pTab->p.pConfig;
  int eType0;                     /* value_type() of apVal[0] */
  int rc = SQLITE_OK;             /* Return code */
  int bUpdateOrDelete = 0;


  /* A transaction must be open when this is called. */
  assert( pTab->ts.eState==1 || pTab->ts.eState==2 );

  assert( pVtab->zErrMsg==0 );
  assert( nArg==1 || nArg==(2+pConfig->nCol+2) );
  assert( sqlite3_value_type(apVal[0])==SQLITE_INTEGER
       || sqlite3_value_type(apVal[0])==SQLITE_NULL

   && sqlite3_value_type(apVal[2+pConfig->nCol])!=SQLITE_NULL
  ){
    /* A "special" INSERT op. These are handled separately. */
    const char *z = (const char*)sqlite3_value_text(apVal[2+pConfig->nCol]);
    if( pConfig->eContent!=FTS5_CONTENT_NORMAL
      && 0==sqlite3_stricmp("delete", z)
    ){
      if( pConfig->bContentlessDelete ){
        fts5SetVtabError(pTab,
            "'delete' may not be used with a contentless_delete=1 table"
        );
        rc = SQLITE_ERROR;
      }else{
        rc = fts5SpecialDelete(pTab, apVal);
      }
    }else{
      rc = fts5SpecialInsert(pTab, z, apVal[2 + pConfig->nCol + 1]);
    }
  }else{
    /* A regular INSERT, UPDATE or DELETE statement. The trick here is that
    ** any conflict on the rowid value must be detected before any
    ** modifications are made to the database file. There are 4 cases:
    **
    **   1) DELETE
    **   2) UPDATE (rowid not modified)
    **   3) UPDATE (rowid modified)
    **   4) INSERT
    **
    ** Cases 3 and 4 may violate the rowid constraint.
    */
    int eConflict = SQLITE_ABORT;
    if( pConfig->eContent==FTS5_CONTENT_NORMAL || pConfig->bContentlessDelete ){
      eConflict = sqlite3_vtab_on_conflict(pConfig->db);
    }

    assert( eType0==SQLITE_INTEGER || eType0==SQLITE_NULL );
    assert( nArg!=1 || eType0==SQLITE_INTEGER );

    /* Filter out attempts to run UPDATE or DELETE on contentless tables.
    ** This is not suported. Except - DELETE is supported if the CREATE
    ** VIRTUAL TABLE statement contained "contentless_delete=1". */
    if( eType0==SQLITE_INTEGER
     && pConfig->eContent==FTS5_CONTENT_NONE
     && (nArg>1 || pConfig->bContentlessDelete==0)
    ){
      pTab->p.base.zErrMsg = sqlite3_mprintf(
          "cannot %s contentless fts5 table: %s",
          (nArg>1 ? "UPDATE" : "DELETE from"), pConfig->zName
      );
      rc = SQLITE_ERROR;
    }

** Implementation of xSync() method.
*/
static int fts5SyncMethod(sqlite3_vtab *pVtab){
  int rc;
  Fts5FullTable *pTab = (Fts5FullTable*)pVtab;
  fts5CheckTransactionState(pTab, FTS5_SYNC, 0);
  pTab->p.pConfig->pzErrmsg = &pTab->p.base.zErrMsg;

  rc = sqlite3Fts5FlushToDisk(&pTab->p);
  pTab->p.pConfig->pzErrmsg = 0;
  return rc;
}

/*
** Implementation of xBegin() method.
*/

static void fts5SourceIdFunc(
  sqlite3_context *pCtx,          /* Function call context */
  int nArg,                       /* Number of args */
  sqlite3_value **apUnused        /* Function arguments */
){
  assert( nArg==0 );
  UNUSED_PARAM2(nArg, apUnused);
  sqlite3_result_text(pCtx, "fts5: 2023-08-01 11:03:06 aa55c83f35c2ab134e0842201e46e021079283f9c65595c86664060b3aa8d715", -1, SQLITE_TRANSIENT);
}

/*
** Return true if zName is the extension on one of the shadow tables used
** by this module.
*/
static int fts5ShadowName(const char *zName){

      "SELECT %s FROM %s T WHERE T.%Q >= ? AND T.%Q <= ? ORDER BY T.%Q ASC",
      "SELECT %s FROM %s T WHERE T.%Q <= ? AND T.%Q >= ? ORDER BY T.%Q DESC",
      "SELECT %s FROM %s T WHERE T.%Q=?",               /* LOOKUP  */

      "INSERT INTO %Q.'%q_content' VALUES(%s)",         /* INSERT_CONTENT  */
      "REPLACE INTO %Q.'%q_content' VALUES(%s)",        /* REPLACE_CONTENT */
      "DELETE FROM %Q.'%q_content' WHERE id=?",         /* DELETE_CONTENT  */
      "REPLACE INTO %Q.'%q_docsize' VALUES(?,?%s)",     /* REPLACE_DOCSIZE  */
      "DELETE FROM %Q.'%q_docsize' WHERE id=?",         /* DELETE_DOCSIZE  */

      "SELECT sz%s FROM %Q.'%q_docsize' WHERE id=?",    /* LOOKUP_DOCSIZE  */

      "REPLACE INTO %Q.'%q_config' VALUES(?,?)",        /* REPLACE_CONFIG */
      "SELECT %s FROM %s AS T",                         /* SCAN */
    };
    Fts5Config *pC = p->pConfig;
    char *zSql = 0;