** See the graph on check-in 8ac66ef33b464d28 for example
        **    iReuseIdx = -1;
        **    iReuseRail = -1; */
        isCherrypick = 1;
      }
      pDesc = hashFind(p, parentRid);
      if( pDesc==0 ){
        int iMrail = -1;
        /* Merge from a node that is off-screen */
        if( iReuseIdx>=p->nRow+1 ){
          continue;  /* Suppress multiple off-screen merges */
        }
        int iMrail = -1;
        for(j=0; j<GR_MAX_RAIL; j++){
          if( mergeRiserFrom[j]==parentRid ){
            iMrail = j;
            break;
          }
        }
        if( iMrail==-1 ){