Fossil

** zDbName is NULL. Returns NULL if globalDb is not opened.
*/
const char * fiddle_db_filename(const char * zDbName){
    return globalDb
      ? sqlite3_db_filename(globalDb, zDbName ? zDbName : "main")
      : NULL;
}

/*
** Closes, unlinks, and reopens the db using its current filename (or
** the default if the db is currently closed). It is assumed, for
** purposes of the fiddle build, that the file is in a transient
** virtual filesystem within the browser.
*/
void fiddle_reset_db(void){
  char *zFilename = 0;
  if(0==globalDb){
    shellState.pAuxDb->zDbFilename = "/fiddle.sqlite3";
  }else{
    zFilename =
      sqlite3_mprintf("%s", sqlite3_db_filename(globalDb, "main"));
    shell_check_oom(zFilename);
    close_db(globalDb);
    shellDeleteFile(zFilename);
    shellState.db = 0;
    shellState.pAuxDb->zDbFilename = zFilename;
  }
  open_db(&shellState, 0);
  sqlite3_free(zFilename);
}

/*
** Trivial exportable function for emscripten. Needs to be exported using:
**
** emcc ..flags... -sEXPORTED_FUNCTIONS=_fiddle_exec -sEXPORTED_RUNTIME_METHODS=ccall,cwrap
**
** (Note the underscore before the function name.) It processes zSql

    printf(
        "SQLite version %s %.19s\n" /*extra-version-info*/,
        sqlite3_libversion(), sqlite3_sourceid()
    );
    puts("WASM shell");
    puts("Enter \".help\" for usage hints.");
    if(once>0){

      fiddle_reset_db();
    }
    if(shellState.db){
      printf("Connected to %s.\n", fiddle_db_filename(NULL));
    }else{
      fprintf(stderr,"ERROR initializing db!\n");
      return;
    }

**
** See also: [sqlite3_libversion()],
** [sqlite3_libversion_number()], [sqlite3_sourceid()],
** [sqlite_version()] and [sqlite_source_id()].
*/
#define SQLITE_VERSION        "3.39.0"
#define SQLITE_VERSION_NUMBER 3039000
#define SQLITE_SOURCE_ID      "2022-06-03 14:08:40 d18818afc6021a32989499c26ab38fa442e5a55e662e39bb06e5c0daa9c65e25"

/*
** 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

/*
** CAPI3REF: Return The Schema Name For A Database Connection
** METHOD: sqlite3
**
** ^The sqlite3_db_name(D,N) interface returns a pointer to the schema name
** for the N-th database on database connection D, or a NULL pointer of N is
** out of range.  An N alue of 0 means the main database file.  An N of 1 is
** the "temp" schema.  Larger values of N correspond to various ATTACH-ed
** databases.
**
** Space to hold the string that is returned by sqlite3_db_name() is managed
** by SQLite itself.  The string might be deallocated by any operation that
** changes the schema, including [ATTACH] or [DETACH] or calls to
** [sqlite3_serialize()] or [sqlite3_deserialize()], even operations that
** occur on a different thread.  Applications that need to
** remember the string long-term should make their own copy.  Applications that

/*                           0x0200 -- available for reuse */
#define SQLITE_FUNC_UNLIKELY 0x0400 /* Built-in unlikely() function */
#define SQLITE_FUNC_CONSTANT 0x0800 /* Constant inputs give a constant output */
#define SQLITE_FUNC_MINMAX   0x1000 /* True for min() and max() aggregates */
#define SQLITE_FUNC_SLOCHNG  0x2000 /* "Slow Change". Value constant during a
                                    ** single query - might change over time */
#define SQLITE_FUNC_TEST     0x4000 /* Built-in testing functions */
/*                           0x8000 -- available for reuse */
#define SQLITE_FUNC_WINDOW   0x00010000 /* Built-in window-only function */
#define SQLITE_FUNC_INTERNAL 0x00040000 /* For use by NestedParse() only */
#define SQLITE_FUNC_DIRECT   0x00080000 /* Not for use in TRIGGERs or VIEWs */
#define SQLITE_FUNC_SUBTYPE  0x00100000 /* Result likely to have sub-type */
#define SQLITE_FUNC_UNSAFE   0x00200000 /* Function has side effects */
#define SQLITE_FUNC_INLINE   0x00400000 /* Functions implemented in-line */
#define SQLITE_FUNC_BUILTIN  0x00800000 /* This is a built-in function */
#define SQLITE_FUNC_ANYORDER 0x08000000 /* count/min/max aggregate */

/* Identifier numbers for each in-line function */
#define INLINEFUNC_coalesce             0
#define INLINEFUNC_implies_nonnull_row  1
#define INLINEFUNC_expr_implies_expr    2
#define INLINEFUNC_expr_compare         3
#define INLINEFUNC_affinity             4
#define INLINEFUNC_iif                  5
#define INLINEFUNC_sqlite_offset        6
#define INLINEFUNC_unlikely            99  /* Default case */

/*
** The following three macros, FUNCTION(), LIKEFUNC() and AGGREGATE() are
** used to create the initializers for the FuncDef structures.
**
**   FUNCTION(zName, nArg, iArg, bNC, xFunc)

    }
    if( rc ) return rc;
  }

  TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
          pCur->pgnoRoot, pX->nKey, pX->nData, pPage->pgno,
          loc==0 ? "overwrite" : "new entry"));
  assert( pPage->isInit || CORRUPT_DB );
  newCell = pBt->pTmpSpace;
  assert( newCell!=0 );
  if( flags & BTREE_PREFORMAT ){
    rc = SQLITE_OK;
    szNew = pBt->nPreformatSize;
    if( szNew<4 ) szNew = 4;
    if( ISAUTOVACUUM && szNew>pPage->maxLocal ){

    case INLINEFUNC_iif: {
      Expr caseExpr;
      memset(&caseExpr, 0, sizeof(caseExpr));
      caseExpr.op = TK_CASE;
      caseExpr.x.pList = pFarg;
      return sqlite3ExprCodeTarget(pParse, &caseExpr, target);
    }
#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
    case INLINEFUNC_sqlite_offset: {
      Expr *pArg = pFarg->a[0].pExpr;
      if( pArg->op==TK_COLUMN && pArg->iTable>=0 ){
        sqlite3VdbeAddOp3(v, OP_Offset, pArg->iTable, pArg->iColumn, target);
      }else{
        sqlite3VdbeAddOp2(v, OP_Null, 0, target);
      }
      break;
    }
#endif
    default: {
      /* The UNLIKELY() function is a no-op.  The result is the value
      ** of the first argument.
      */
      assert( nFarg==1 || nFarg==2 );
      target = sqlite3ExprCodeTarget(pParse, pFarg->a[0].pExpr, target);
      break;

        pDef = sqlite3VtabOverloadFunction(db, pDef, nFarg, pFarg->a[0].pExpr);
      }
#endif
      if( pDef->funcFlags & SQLITE_FUNC_NEEDCOLL ){
        if( !pColl ) pColl = db->pDfltColl;
        sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
      }











      sqlite3VdbeAddFunctionCall(pParse, constMask, r1, target, nFarg,
                                 pDef, pExpr->op2);

      if( nFarg ){
        if( constMask==0 ){
          sqlite3ReleaseTempRange(pParse, r1, nFarg);
        }else{
          sqlite3VdbeReleaseRegisters(pParse, r1, nFarg, constMask, 1);
        }
      }

    if( pStep->pSelect ){
      sqlite3SelectPrep(pParse, pStep->pSelect, &sNC);
      if( pParse->nErr ) rc = pParse->rc;
    }
    if( rc==SQLITE_OK && pStep->zTarget ){
      SrcList *pSrc = sqlite3TriggerStepSrc(pParse, pStep);
      if( pSrc ){
        Select *pSel = sqlite3SelectNew(
            pParse, pStep->pExprList, pSrc, 0, 0, 0, 0, 0, 0
        );
        if( pSel==0 ){
          pStep->pExprList = 0;
          pSrc = 0;
          rc = SQLITE_NOMEM;
        }else{
          sqlite3SelectPrep(pParse, pSel, 0);
          rc = pParse->nErr ? SQLITE_ERROR : SQLITE_OK;
          assert( pStep->pExprList==0 || pStep->pExprList==pSel->pEList );
          assert( pSrc==pSel->pSrc );
          if( pStep->pExprList ) pSel->pEList = 0;
          pSel->pSrc = 0;
          sqlite3SelectDelete(db, pSel);
        }
        if( pStep->pFrom ){
          int i;
          for(i=0; i<pStep->pFrom->nSrc && rc==SQLITE_OK; i++){
            SrcItem *p = &pStep->pFrom->a[i];

            if( p->pSelect ){
              sqlite3SelectPrep(pParse, p->pSelect, 0);











            }
          }
        }

        if(  db->mallocFailed ){
          rc = SQLITE_NOMEM;
        }
        sNC.pSrcList = pSrc;
        if( rc==SQLITE_OK && pStep->pWhere ){
          rc = sqlite3ResolveExprNames(&sNC, pStep->pWhere);
        }
        if( rc==SQLITE_OK ){

        if( isLegacy==0 ){
          rc = renameResolveTrigger(&sParse);
          if( rc==SQLITE_OK ){
            renameWalkTrigger(&sWalker, pTrigger);
            for(pStep=pTrigger->step_list; pStep; pStep=pStep->pNext){
              if( pStep->zTarget && 0==sqlite3_stricmp(pStep->zTarget, zOld) ){
                renameTokenFind(&sParse, &sCtx, pStep->zTarget);
              }
              if( pStep->pFrom ){
                int i;
                for(i=0; i<pStep->pFrom->nSrc; i++){
                  SrcItem *pItem = &pStep->pFrom->a[i];
                  if( 0==sqlite3_stricmp(pItem->zName, zOld) ){
                    renameTokenFind(&sParse, &sCtx, pItem->zName);
                  }
                }
              }
            }
          }
        }
      }
#endif
    }

    DFUNCTION(sqlite_compileoption_used,1, 0, 0, compileoptionusedFunc  ),
    DFUNCTION(sqlite_compileoption_get, 1, 0, 0, compileoptiongetFunc  ),
#endif /* SQLITE_OMIT_COMPILEOPTION_DIAGS */
    INLINE_FUNC(unlikely,        1, INLINEFUNC_unlikely, SQLITE_FUNC_UNLIKELY),
    INLINE_FUNC(likelihood,      2, INLINEFUNC_unlikely, SQLITE_FUNC_UNLIKELY),
    INLINE_FUNC(likely,          1, INLINEFUNC_unlikely, SQLITE_FUNC_UNLIKELY),
#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC

    INLINE_FUNC(sqlite_offset,   1, INLINEFUNC_sqlite_offset, 0 ),
#endif
    FUNCTION(ltrim,              1, 1, 0, trimFunc         ),
    FUNCTION(ltrim,              2, 1, 0, trimFunc         ),
    FUNCTION(rtrim,              1, 2, 0, trimFunc         ),
    FUNCTION(rtrim,              2, 2, 0, trimFunc         ),
    FUNCTION(trim,               1, 3, 0, trimFunc         ),
    FUNCTION(trim,               2, 3, 0, trimFunc         ),

      Expr *pColExpr = sqlite3ExprSkipCollateAndLikely(pX->pExpr);
      while( ALWAYS(pColExpr!=0) && pColExpr->op==TK_DOT ){
        pColExpr = pColExpr->pRight;
        assert( pColExpr!=0 );
      }
      if( pColExpr->op==TK_COLUMN
       && ALWAYS( ExprUseYTab(pColExpr) )
       && ALWAYS( pColExpr->y.pTab!=0 )
      ){
        /* For columns use the column name name */
        int iCol = pColExpr->iColumn;
        pTab = pColExpr->y.pTab;
        if( iCol<0 ) iCol = pTab->iPKey;
        zName = iCol>=0 ? pTab->aCol[iCol].zCnName : "rowid";
      }else if( pColExpr->op==TK_ID ){
        assert( !ExprHasProperty(pColExpr, EP_IntValue) );
        zName = pColExpr->u.zToken;
      }else{
        /* Use the original text of the column expression as its name */

        }
        if( ExprHasProperty(pExpr,EP_OuterON|EP_InnerON) ){
          sqlite3SetJoinExpr(pNew, pExpr->w.iJoin,
                             pExpr->flags & (EP_OuterON|EP_InnerON));
        }
        sqlite3ExprDelete(db, pExpr);
        pExpr = pNew;
        if( pExpr->op==TK_TRUEFALSE ){
          pExpr->u.iValue = sqlite3ExprTruthValue(pExpr);
          pExpr->op = TK_INTEGER;
          ExprSetProperty(pExpr, EP_IntValue);
        }

        /* Ensure that the expression now has an implicit collation sequence,
        ** just as it did when it was a column of a view or sub-query. */
        if( pExpr->op!=TK_COLUMN && pExpr->op!=TK_COLLATE ){
          CollSeq *pColl = sqlite3ExprCollSeq(pSubst->pParse, pExpr);
          pExpr = sqlite3ExprAddCollateString(pSubst->pParse, pExpr,
              (pColl ? pColl->zName : "BINARY")

** Construct a trigger step that implements an UPDATE statement and return
** a pointer to that trigger step.  The parser calls this routine when it
** sees an UPDATE statement inside the body of a CREATE TRIGGER.
*/
SQLITE_PRIVATE TriggerStep *sqlite3TriggerUpdateStep(
  Parse *pParse,          /* Parser */
  Token *pTableName,   /* Name of the table to be updated */
  SrcList *pFrom,      /* FROM clause for an UPDATE-FROM, or NULL */
  ExprList *pEList,    /* The SET clause: list of column and new values */
  Expr *pWhere,        /* The WHERE clause */
  u8 orconf,           /* The conflict algorithm. (OE_Abort, OE_Ignore, etc) */
  const char *zStart,  /* Start of SQL text */
  const char *zEnd     /* End of SQL text */
){
  sqlite3 *db = pParse->db;

    Schema *pSchema = pStep->pTrig->pSchema;
    pSrc->a[0].zName = zName;
    if( pSchema!=db->aDb[1].pSchema ){
      pSrc->a[0].pSchema = pSchema;
    }
    if( pStep->pFrom ){
      SrcList *pDup = sqlite3SrcListDup(db, pStep->pFrom, 0);
      if( pDup && pDup->nSrc>1 && !IN_RENAME_OBJECT ){
        Select *pSubquery;
        Token as;
        pSubquery = sqlite3SelectNew(pParse,0,pDup,0,0,0,0,SF_NestedFrom,0);
        as.n = 0;
        as.z = 0;
        pDup = sqlite3SrcListAppendFromTerm(pParse,0,0,0,&as,pSubquery,0);
      }
      pSrc = sqlite3SrcListAppendList(pParse, pSrc, pDup);
    }
  }else{
    sqlite3DbFree(db, zName);
  }
  return pSrc;
}

#define WO_AUX    0x0040       /* Op useful to virtual tables only */
#define WO_IS     0x0080
#define WO_ISNULL 0x0100
#define WO_OR     0x0200       /* Two or more OR-connected terms */
#define WO_AND    0x0400       /* Two or more AND-connected terms */
#define WO_EQUIV  0x0800       /* Of the form A==B, both columns */
#define WO_NOOP   0x1000       /* This term does not restrict search space */
#define WO_ROWVAL 0x2000       /* A row-value term */

#define WO_ALL    0x3fff       /* Mask of all possible WO_* values */
#define WO_SINGLE 0x01ff       /* Mask of all non-compound WO_* values */

/*
** These are definitions of bits in the WhereLoop.wsFlags field.
** The particular combination of bits in each WhereLoop help to
** determine the algorithm that WhereLoop represents.
*/

      pE = pTerm->pExpr;
      assert( pE!=0 );
      if( pTabItem->fg.jointype & (JT_LEFT|JT_LTORJ|JT_RIGHT) ){
        if( !ExprHasProperty(pE,EP_OuterON|EP_InnerON) ){
          /* Defer processing WHERE clause constraints until after outer
          ** join processing.  tag-20220513a */
          continue;
        }else if( (pTabItem->fg.jointype & JT_LEFT)==JT_LEFT
               && !ExprHasProperty(pE,EP_OuterON) ){
          continue;
        }else{
          Bitmask m = sqlite3WhereGetMask(&pWInfo->sMaskSet, pE->w.iJoin);
          if( m & pLevel->notReady ){
            /* An ON clause that is not ripe */
            continue;
          }
        }

      sqlite3VdbeAddOp1(v, OP_NullRow, iIdxCur);
    }
  }
  if( (pTabItem->fg.jointype & JT_LTORJ)==0 ){
    mAll |= pLoop->maskSelf;
    for(k=0; k<pWC->nTerm; k++){
      WhereTerm *pTerm = &pWC->a[k];
      if( (pTerm->wtFlags & (TERM_VIRTUAL|TERM_SLICE))!=0
       && pTerm->eOperator!=WO_ROWVAL
      ){
        break;
      }
      if( pTerm->prereqAll & ~mAll ) continue;
      if( ExprHasProperty(pTerm->pExpr, EP_OuterON|EP_InnerON) ) continue;
      pSubWhere = sqlite3ExprAnd(pParse, pSubWhere,
                                 sqlite3ExprDup(pParse->db, pTerm->pExpr, 0));
    }
  }
  sFrom.nSrc = 1;

  }
  if( pMaskSet->bVarSelect ) pTerm->wtFlags |= TERM_VARSELECT;

#ifdef SQLITE_DEBUG
  if( prereqAll!=sqlite3WhereExprUsageNN(pMaskSet, pExpr) ){
    printf("\n*** Incorrect prereqAll computed for:\n");
    sqlite3TreeViewExpr(0,pExpr,0);
    assert( 0 );
  }
#endif

  if( ExprHasProperty(pExpr, EP_OuterON|EP_InnerON) ){
    Bitmask x = sqlite3WhereGetMask(pMaskSet, pExpr->w.iJoin);
    if( ExprHasProperty(pExpr, EP_OuterON) ){
      prereqAll |= x;

      pNew = sqlite3PExpr(pParse, pExpr->op, pLeft, pRight);
      transferJoinMarkings(pNew, pExpr);
      idxNew = whereClauseInsert(pWC, pNew, TERM_DYNAMIC|TERM_SLICE);
      exprAnalyze(pSrc, pWC, idxNew);
    }
    pTerm = &pWC->a[idxTerm];
    pTerm->wtFlags |= TERM_CODED|TERM_VIRTUAL;  /* Disable the original */
    pTerm->eOperator = WO_ROWVAL;
  }

  /* If there is a vector IN term - e.g. "(a, b) IN (SELECT ...)" - create
  ** a virtual term for each vector component. The expression object
  ** used by each such virtual term is pExpr (the full vector IN(...)
  ** expression). The WhereTerm.u.x.iField variable identifies the index within
  ** the vector on the LHS that the virtual term represents.

    /* Check condition (4). Return early if it is not met. */
    for(ii=0; ii<pWC->nTerm; ii++){
      if( pWC->a[ii].wtFlags & TERM_CODED ){
        /* This term is a vector operation that has been decomposed into
        ** other, subsequent terms.  It can be ignored. See tag-20220128a */
        assert( pWC->a[ii].wtFlags & TERM_VIRTUAL );
        assert( pWC->a[ii].eOperator==WO_ROWVAL );
        continue;
      }
      if( pWC->a[ii].leftCursor!=iCsr ) return;
    }

    /* Check condition (5). Return early if it is not met. */
    if( pOrderBy ){

  Vdbe *v = pParse->pVdbe;
  int i;
  WhereLevel *pLevel;
  WhereLoop *pLoop;
  SrcList *pTabList = pWInfo->pTabList;
  sqlite3 *db = pParse->db;
  int iEnd = sqlite3VdbeCurrentAddr(v);
  int nRJ = 0;

  /* Generate loop termination code.
  */
  VdbeModuleComment((v, "End WHERE-core"));
  for(i=pWInfo->nLevel-1; i>=0; i--){
    int addr;
    pLevel = &pWInfo->a[i];
    if( pLevel->pRJ ){
      /* Terminate the subroutine that forms the interior of the loop of
      ** the RIGHT JOIN table */
      WhereRightJoin *pRJ = pLevel->pRJ;
      sqlite3VdbeResolveLabel(v, pLevel->addrCont);
      pLevel->addrCont = 0;
      pRJ->endSubrtn = sqlite3VdbeCurrentAddr(v);
      sqlite3VdbeAddOp3(v, OP_Return, pRJ->regReturn, pRJ->addrSubrtn, 1);
      VdbeCoverage(v);

      nRJ++;
    }
    pLoop = pLevel->pWLoop;
    if( pLevel->op!=OP_Noop ){
#ifndef SQLITE_DISABLE_SKIPAHEAD_DISTINCT
      int addrSeek = 0;
      Index *pIdx;
      int n;

  */
  sqlite3VdbeResolveLabel(v, pWInfo->iBreak);

  /* Final cleanup
  */
  pParse->nQueryLoop = pWInfo->savedNQueryLoop;
  whereInfoFree(db, pWInfo);
  pParse->withinRJSubrtn -= nRJ;
  return;
}

/************** End of where.c ***********************************************/
/************** Begin file window.c ******************************************/
/*
** 2018 May 08

      blobGrowBuffer(&pNode->key, nTerm, &rc);

      if( rc==SQLITE_OK ){
        if( pNode->key.n ){
          pBlk->n += sqlite3Fts3PutVarint(&pBlk->a[pBlk->n], nPrefix);
        }
        pBlk->n += sqlite3Fts3PutVarint(&pBlk->a[pBlk->n], nSuffix);
        assert( nPrefix+nSuffix<=nTerm );
        assert( nPrefix>=0 );
        memcpy(&pBlk->a[pBlk->n], &zTerm[nPrefix], nSuffix);
        pBlk->n += nSuffix;

        memcpy(pNode->key.a, zTerm, nTerm);
        pNode->key.n = nTerm;
      }
    }else{

  int nPrefix;                  /* Size of prefix shared with previous term */
  int nSuffix;                  /* Size of suffix (nTerm - nPrefix) */
  NodeWriter *pLeaf;            /* Object used to write leaf nodes */

  pLeaf = &pWriter->aNodeWriter[0];
  nPrefix = fts3PrefixCompress(pLeaf->key.a, pLeaf->key.n, zTerm, nTerm);
  nSuffix = nTerm - nPrefix;
  if(nSuffix<=0 ) return FTS_CORRUPT_VTAB;

  nSpace  = sqlite3Fts3VarintLen(nPrefix);
  nSpace += sqlite3Fts3VarintLen(nSuffix) + nSuffix;
  nSpace += sqlite3Fts3VarintLen(nDoclist) + nDoclist;

  /* If the current block is not empty, and if adding this term/doclist
  ** to the current block would make it larger than Fts3Table.nNodeSize

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: 2022-06-03 14:08:40 d18818afc6021a32989499c26ab38fa442e5a55e662e39bb06e5c0daa9c65e25", -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){

**
** See also: [sqlite3_libversion()],
** [sqlite3_libversion_number()], [sqlite3_sourceid()],
** [sqlite_version()] and [sqlite_source_id()].
*/
#define SQLITE_VERSION        "3.39.0"
#define SQLITE_VERSION_NUMBER 3039000
#define SQLITE_SOURCE_ID      "2022-06-03 14:08:40 d18818afc6021a32989499c26ab38fa442e5a55e662e39bb06e5c0daa9c65e25"

/*
** 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

/*
** CAPI3REF: Return The Schema Name For A Database Connection
** METHOD: sqlite3
**
** ^The sqlite3_db_name(D,N) interface returns a pointer to the schema name
** for the N-th database on database connection D, or a NULL pointer of N is
** out of range.  An N alue of 0 means the main database file.  An N of 1 is
** the "temp" schema.  Larger values of N correspond to various ATTACH-ed
** databases.
**
** Space to hold the string that is returned by sqlite3_db_name() is managed
** by SQLite itself.  The string might be deallocated by any operation that
** changes the schema, including [ATTACH] or [DETACH] or calls to
** [sqlite3_serialize()] or [sqlite3_deserialize()], even operations that
** occur on a different thread.  Applications that need to
** remember the string long-term should make their own copy.  Applications that