WhereInfo *sqlite3WhereBegin(
  Parse *pParse,          /* The parser context */
  SrcList *pTabList,      /* FROM clause: A list of all tables to be scanned */
  Expr *pWhere,           /* The WHERE clause */
  ExprList *pOrderBy,     /* An ORDER BY (or GROUP BY) clause, or NULL */
  ExprList *pResultSet,   /* Query result set.  Req'd for DISTINCT */
  Select *pLimit,         /* Use this LIMIT/OFFSET clause, if any */
  u16 wctrlFlags,         /* The WHERE_* flags defined in sqliteInt.h */
  int iAuxArg             /* If WHERE_OR_SUBCLAUSE is set, index cursor number
                          ** If WHERE_USE_LIMIT, then the limit amount */
){
  int nByteWInfo;            /* Num. bytes allocated for WhereInfo struct */
  int nTabList;              /* Number of elements in pTabList */
  WhereInfo *pWInfo;         /* Will become the return value of this function */
  Vdbe *v = pParse->pVdbe;   /* The virtual database engine */
  Bitmask notReady;          /* Cursors that are not yet positioned */
  WhereLoopBuilder sWLB;     /* The WhereLoop builder */
  WhereMaskSet *pMaskSet;    /* The expression mask set */
  WhereLevel *pLevel;        /* A single level in pWInfo->a[] */
  WhereLoop *pLoop;          /* Pointer to a single WhereLoop object */
  int ii;                    /* Loop counter */
  sqlite3 *db;               /* Database connection */
  int rc;                    /* Return code */
  u8 bFordelete = 0;         /* OPFLAG_FORDELETE or zero, as appropriate */

  assert( (wctrlFlags & WHERE_ONEPASS_MULTIROW)==0 || (
        (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 
     && (wctrlFlags & WHERE_OR_SUBCLAUSE)==0 
  ));

  /* Only one of WHERE_OR_SUBCLAUSE or WHERE_USE_LIMIT */
  assert( (wctrlFlags & WHERE_OR_SUBCLAUSE)==0
            || (wctrlFlags & WHERE_USE_LIMIT)==0 );

  /* Variable initialization */
  db = pParse->db;
  memset(&sWLB, 0, sizeof(sWLB));

  /* An ORDER/GROUP BY clause of more than 63 terms cannot be optimized */
  testcase( pOrderBy && pOrderBy->nExpr==BMS-1 );
  if( pOrderBy && pOrderBy->nExpr>=BMS ) pOrderBy = 0;

  /* The number of tables in the FROM clause is limited by the number of
  ** bits in a Bitmask 
  */
  testcase( pTabList->nSrc==BMS );
  if( pTabList->nSrc>BMS ){
    sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
    return 0;
  }

  /* This function normally generates a nested loop for all tables in 
  ** pTabList.  But if the WHERE_OR_SUBCLAUSE flag is set, then we should
  ** only generate code for the first table in pTabList and assume that
  ** any cursors associated with subsequent tables are uninitialized.
  */
  nTabList = (wctrlFlags & WHERE_OR_SUBCLAUSE) ? 1 : pTabList->nSrc;

  /* Allocate and initialize the WhereInfo structure that will become the
  ** return value. A single allocation is used to store the WhereInfo
  ** struct, the contents of WhereInfo.a[], the WhereClause structure
  ** and the WhereMaskSet structure. Since WhereClause contains an 8-byte
  ** field (type Bitmask) it must be aligned on an 8-byte boundary on
  ** some architectures. Hence the ROUND8() below.
  */
  nByteWInfo = ROUND8P(sizeof(WhereInfo)+(nTabList-1)*sizeof(WhereLevel));
  pWInfo = sqlite3DbMallocRawNN(db, nByteWInfo + sizeof(WhereLoop));
  if( db->mallocFailed ){
    sqlite3DbFree(db, pWInfo);
    pWInfo = 0;
    goto whereBeginError;
  }
  pWInfo->pParse = pParse;
  pWInfo->pTabList = pTabList;
  pWInfo->pOrderBy = pOrderBy;
  pWInfo->pWhere = pWhere;
  pWInfo->pResultSet = pResultSet;
  pWInfo->aiCurOnePass[0] = pWInfo->aiCurOnePass[1] = -1;
  pWInfo->nLevel = nTabList;
  pWInfo->iBreak = pWInfo->iContinue = sqlite3VdbeMakeLabel(pParse);
  pWInfo->wctrlFlags = wctrlFlags;
  pWInfo->iLimit = iAuxArg;
  pWInfo->savedNQueryLoop = pParse->nQueryLoop;
#ifndef SQLITE_OMIT_VIRTUALTABLE
  pWInfo->pLimit = pLimit;
#endif
  memset(&pWInfo->nOBSat, 0, 
         offsetof(WhereInfo,sWC) - offsetof(WhereInfo,nOBSat));
  memset(&pWInfo->a[0], 0, sizeof(WhereLoop)+nTabList*sizeof(WhereLevel));
  assert( pWInfo->eOnePass==ONEPASS_OFF );  /* ONEPASS defaults to OFF */
  pMaskSet = &pWInfo->sMaskSet;
  pMaskSet->n = 0;
  pMaskSet->ix[0] = -99; /* Initialize ix[0] to a value that can never be
                         ** a valid cursor number, to avoid an initial
                         ** test for pMaskSet->n==0 in sqlite3WhereGetMask() */
  sWLB.pWInfo = pWInfo;
  sWLB.pWC = &pWInfo->sWC;
  sWLB.pNew = (WhereLoop*)(((char*)pWInfo)+nByteWInfo);
  assert( EIGHT_BYTE_ALIGNMENT(sWLB.pNew) );
  whereLoopInit(sWLB.pNew);
#ifdef SQLITE_DEBUG
  sWLB.pNew->cId = '*';
#endif

  /* Split the WHERE clause into separate subexpressions where each
  ** subexpression is separated by an AND operator.
  */
  sqlite3WhereClauseInit(&pWInfo->sWC, pWInfo);
  sqlite3WhereSplit(&pWInfo->sWC, pWhere, TK_AND);
    
  /* Special case: No FROM clause
  */
  if( nTabList==0 ){
    if( pOrderBy ) pWInfo->nOBSat = pOrderBy->nExpr;
    if( (wctrlFlags & WHERE_WANT_DISTINCT)!=0
     && OptimizationEnabled(db, SQLITE_DistinctOpt)
    ){
      pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
    }
    ExplainQueryPlan((pParse, 0, "SCAN CONSTANT ROW"));
  }else{
    /* Assign a bit from the bitmask to every term in the FROM clause.
    **
    ** The N-th term of the FROM clause is assigned a bitmask of 1<<N.
    **
    ** The rule of the previous sentence ensures thta if X is the bitmask for
    ** a table T, then X-1 is the bitmask for all other tables to the left of T.
    ** Knowing the bitmask for all tables to the left of a left join is
    ** important.  Ticket #3015.
    **
    ** Note that bitmasks are created for all pTabList->nSrc tables in
    ** pTabList, not just the first nTabList tables.  nTabList is normally
    ** equal to pTabList->nSrc but might be shortened to 1 if the
    ** WHERE_OR_SUBCLAUSE flag is set.
    */
    ii = 0;
    do{
      createMask(pMaskSet, pTabList->a[ii].iCursor);
      sqlite3WhereTabFuncArgs(pParse, &pTabList->a[ii], &pWInfo->sWC);
    }while( (++ii)<pTabList->nSrc );
  #ifdef SQLITE_DEBUG
    {
      Bitmask mx = 0;
      for(ii=0; ii<pTabList->nSrc; ii++){
        Bitmask m = sqlite3WhereGetMask(pMaskSet, pTabList->a[ii].iCursor);
        assert( m>=mx );
        mx = m;
      }
    }
  #endif
  }
  
  /* Analyze all of the subexpressions. */
  sqlite3WhereExprAnalyze(pTabList, &pWInfo->sWC);
  sqlite3WhereAddLimit(&pWInfo->sWC, pLimit);
  if( pParse->nErr ) goto whereBeginError;

  /* Special case: WHERE terms that do not refer to any tables in the join
  ** (constant expressions). Evaluate each such term, and jump over all the
  ** generated code if the result is not true.  
  **
  ** Do not do this if the expression contains non-deterministic functions
  ** that are not within a sub-select. This is not strictly required, but
  ** preserves SQLite's legacy behaviour in the following two cases:
  **
  **   FROM ... WHERE random()>0;           -- eval random() once per row
  **   FROM ... WHERE (SELECT random())>0;  -- eval random() once overall
  */
  for(ii=0; ii<sWLB.pWC->nBase; ii++){
    WhereTerm *pT = &sWLB.pWC->a[ii];
    if( pT->wtFlags & TERM_VIRTUAL ) continue;
    if( pT->prereqAll==0 && (nTabList==0 || exprIsDeterministic(pT->pExpr)) ){
      sqlite3ExprIfFalse(pParse, pT->pExpr, pWInfo->iBreak, SQLITE_JUMPIFNULL);
      pT->wtFlags |= TERM_CODED;
    }
  }

  if( wctrlFlags & WHERE_WANT_DISTINCT ){
    if( OptimizationDisabled(db, SQLITE_DistinctOpt) ){
      /* Disable the DISTINCT optimization if SQLITE_DistinctOpt is set via
      ** sqlite3_test_ctrl(SQLITE_TESTCTRL_OPTIMIZATIONS,...) */
      wctrlFlags &= ~WHERE_WANT_DISTINCT;
      pWInfo->wctrlFlags &= ~WHERE_WANT_DISTINCT;
    }else if( isDistinctRedundant(pParse, pTabList, &pWInfo->sWC, pResultSet) ){
      /* The DISTINCT marking is pointless.  Ignore it. */
      pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
    }else if( pOrderBy==0 ){
      /* Try to ORDER BY the result set to make distinct processing easier */
      pWInfo->wctrlFlags |= WHERE_DISTINCTBY;
      pWInfo->pOrderBy = pResultSet;
    }
  }

  /* Construct the WhereLoop objects */
#if defined(WHERETRACE_ENABLED)
  if( sqlite3WhereTrace & 0xffff ){
    sqlite3DebugPrintf("*** Optimizer Start *** (wctrlFlags: 0x%x",wctrlFlags);
    if( wctrlFlags & WHERE_USE_LIMIT ){
      sqlite3DebugPrintf(", limit: %d", iAuxArg);
    }
    sqlite3DebugPrintf(")\n");
    if( sqlite3WhereTrace & 0x100 ){
      Select sSelect;
      memset(&sSelect, 0, sizeof(sSelect));
      sSelect.selFlags = SF_WhereBegin;
      sSelect.pSrc = pTabList;
      sSelect.pWhere = pWhere;
      sSelect.pOrderBy = pOrderBy;
      sSelect.pEList = pResultSet;
      sqlite3TreeViewSelect(0, &sSelect, 0);
    }
  }
  if( sqlite3WhereTrace & 0x100 ){ /* Display all terms of the WHERE clause */
    sqlite3DebugPrintf("---- WHERE clause at start of analysis:\n");
    sqlite3WhereClausePrint(sWLB.pWC);
  }
#endif

  if( nTabList!=1 || whereShortCut(&sWLB)==0 ){
    rc = whereLoopAddAll(&sWLB);
    if( rc ) goto whereBeginError;

#ifdef SQLITE_ENABLE_STAT4
    /* If one or more WhereTerm.truthProb values were used in estimating
    ** loop parameters, but then those truthProb values were subsequently
    ** changed based on STAT4 information while computing subsequent loops,
    ** then we need to rerun the whole loop building process so that all
    ** loops will be built using the revised truthProb values. */
    if( sWLB.bldFlags2 & SQLITE_BLDF2_2NDPASS ){
      WHERETRACE_ALL_LOOPS(pWInfo, sWLB.pWC);
      WHERETRACE(0xffff, 
           ("**** Redo all loop computations due to"
            " TERM_HIGHTRUTH changes ****\n"));
      while( pWInfo->pLoops ){
        WhereLoop *p = pWInfo->pLoops;
        pWInfo->pLoops = p->pNextLoop;
        whereLoopDelete(db, p);
      }
      rc = whereLoopAddAll(&sWLB);
      if( rc ) goto whereBeginError;
    }
#endif
    WHERETRACE_ALL_LOOPS(pWInfo, sWLB.pWC);
  
    wherePathSolver(pWInfo, 0);
    if( db->mallocFailed ) goto whereBeginError;
    if( pWInfo->pOrderBy ){
       wherePathSolver(pWInfo, pWInfo->nRowOut+1);
       if( db->mallocFailed ) goto whereBeginError;
    }
  }
  if( pWInfo->pOrderBy==0 && (db->flags & SQLITE_ReverseOrder)!=0 ){
     pWInfo->revMask = ALLBITS;
  }
  if( pParse->nErr ){
    goto whereBeginError;
  }
  assert( db->mallocFailed==0 );
#ifdef WHERETRACE_ENABLED
  if( sqlite3WhereTrace ){
    sqlite3DebugPrintf("---- Solution nRow=%d", pWInfo->nRowOut);
    if( pWInfo->nOBSat>0 ){
      sqlite3DebugPrintf(" ORDERBY=%d,0x%llx", pWInfo->nOBSat, pWInfo->revMask);
    }
    switch( pWInfo->eDistinct ){
      case WHERE_DISTINCT_UNIQUE: {
        sqlite3DebugPrintf("  DISTINCT=unique");
        break;
      }
      case WHERE_DISTINCT_ORDERED: {
        sqlite3DebugPrintf("  DISTINCT=ordered");
        break;
      }
      case WHERE_DISTINCT_UNORDERED: {
        sqlite3DebugPrintf("  DISTINCT=unordered");
        break;
      }
    }
    sqlite3DebugPrintf("\n");
    for(ii=0; ii<pWInfo->nLevel; ii++){
      sqlite3WhereLoopPrint(pWInfo->a[ii].pWLoop, sWLB.pWC);
    }
  }
#endif

  /* Attempt to omit tables from a join that do not affect the result.
  ** See the comment on whereOmitNoopJoin() for further information.
  **
  ** This query optimization is factored out into a separate "no-inline"
  ** procedure to keep the sqlite3WhereBegin() procedure from becoming
  ** too large.  If sqlite3WhereBegin() becomes too large, that prevents
  ** some C-compiler optimizers from in-lining the 
  ** sqlite3WhereCodeOneLoopStart() procedure, and it is important to
  ** in-line sqlite3WhereCodeOneLoopStart() for performance reasons.
  */
  notReady = ~(Bitmask)0;
  if( pWInfo->nLevel>=2
   && pResultSet!=0                         /* these two combine to guarantee */
   && 0==(wctrlFlags & WHERE_AGG_DISTINCT)  /* condition (1) above */
   && OptimizationEnabled(db, SQLITE_OmitNoopJoin)
  ){
    notReady = whereOmitNoopJoin(pWInfo, notReady);
    nTabList = pWInfo->nLevel;
    assert( nTabList>0 );
  }

  /* Check to see if there are any SEARCH loops that might benefit from
  ** using a Bloom filter.
  */
  if( pWInfo->nLevel>=2
   && OptimizationEnabled(db, SQLITE_BloomFilter)
  ){
    whereCheckIfBloomFilterIsUseful(pWInfo);
  }

#if defined(WHERETRACE_ENABLED)
  if( sqlite3WhereTrace & 0x100 ){ /* Display all terms of the WHERE clause */
    sqlite3DebugPrintf("---- WHERE clause at end of analysis:\n");
    sqlite3WhereClausePrint(sWLB.pWC);
  }
  WHERETRACE(0xffff,("*** Optimizer Finished ***\n"));
#endif
  pWInfo->pParse->nQueryLoop += pWInfo->nRowOut;

  /* If the caller is an UPDATE or DELETE statement that is requesting
  ** to use a one-pass algorithm, determine if this is appropriate.
  **
  ** A one-pass approach can be used if the caller has requested one
  ** and either (a) the scan visits at most one row or (b) each
  ** of the following are true:
  **
  **   * the caller has indicated that a one-pass approach can be used
  **     with multiple rows (by setting WHERE_ONEPASS_MULTIROW), and
  **   * the table is not a virtual table, and
  **   * either the scan does not use the OR optimization or the caller
  **     is a DELETE operation (WHERE_DUPLICATES_OK is only specified
  **     for DELETE).
  **
  ** The last qualification is because an UPDATE statement uses
  ** WhereInfo.aiCurOnePass[1] to determine whether or not it really can
  ** use a one-pass approach, and this is not set accurately for scans
  ** that use the OR optimization.
  */
  assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
  if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 ){
    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))
    )){
      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);
      }
    }
  }

  /* Open all tables in the pTabList and any indices selected for
  ** searching those tables.
  */
  for(ii=0, pLevel=pWInfo->a; ii<nTabList; ii++, pLevel++){
    Table *pTab;     /* Table to open */
    int iDb;         /* Index of database containing table/index */
    SrcItem *pTabItem;

    pTabItem = &pTabList->a[pLevel->iFrom];
    pTab = pTabItem->pTab;
    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
    pLoop = pLevel->pWLoop;
    if( (pTab->tabFlags & TF_Ephemeral)!=0 || IsView(pTab) ){
      /* Do nothing */
    }else
#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){
      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
      int iCur = pTabItem->iCursor;
      sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
    }else if( IsVirtual(pTab) ){
      /* noop */
    }else
#endif
    if( ((pLoop->wsFlags & WHERE_IDX_ONLY)==0
         && (wctrlFlags & WHERE_OR_SUBCLAUSE)==0)
     || (pTabItem->fg.jointype & (JT_LTORJ|JT_RIGHT))!=0
    ){
      int op = OP_OpenRead;
      if( pWInfo->eOnePass!=ONEPASS_OFF ){
        op = OP_OpenWrite;
        pWInfo->aiCurOnePass[0] = pTabItem->iCursor;
      };
      sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
      assert( pTabItem->iCursor==pLevel->iTabCur );
      testcase( pWInfo->eOnePass==ONEPASS_OFF && pTab->nCol==BMS-1 );
      testcase( pWInfo->eOnePass==ONEPASS_OFF && pTab->nCol==BMS );
      if( pWInfo->eOnePass==ONEPASS_OFF 
       && pTab->nCol<BMS
       && (pTab->tabFlags & (TF_HasGenerated|TF_WithoutRowid))==0
       && (pLoop->wsFlags & (WHERE_AUTO_INDEX|WHERE_BLOOMFILTER))==0
      ){
        /* If we know that only a prefix of the record will be used,
        ** it is advantageous to reduce the "column count" field in
        ** the P4 operand of the OP_OpenRead/Write opcode. */
        Bitmask b = pTabItem->colUsed;
        int n = 0;
        for(; b; b=b>>1, n++){}
        sqlite3VdbeChangeP4(v, -1, SQLITE_INT_TO_PTR(n), P4_INT32);
        assert( n<=pTab->nCol );
      }
#ifdef SQLITE_ENABLE_CURSOR_HINTS
      if( pLoop->u.btree.pIndex!=0 ){
        sqlite3VdbeChangeP5(v, OPFLAG_SEEKEQ|bFordelete);
      }else
#endif
      {
        sqlite3VdbeChangeP5(v, bFordelete);
      }
#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
      sqlite3VdbeAddOp4Dup8(v, OP_ColumnsUsed, pTabItem->iCursor, 0, 0,
                            (const u8*)&pTabItem->colUsed, P4_INT64);
#endif
    }else{
      sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
    }
    if( pLoop->wsFlags & WHERE_INDEXED ){
      Index *pIx = pLoop->u.btree.pIndex;
      int iIndexCur;
      int op = OP_OpenRead;
      /* iAuxArg is always set to a positive value if ONEPASS is possible */
      assert( iAuxArg!=0 || (pWInfo->wctrlFlags & WHERE_ONEPASS_DESIRED)==0 );
      if( !HasRowid(pTab) && IsPrimaryKeyIndex(pIx)
       && (wctrlFlags & WHERE_OR_SUBCLAUSE)!=0
      ){
        /* This is one term of an OR-optimization using the PRIMARY KEY of a
        ** WITHOUT ROWID table.  No need for a separate index */
        iIndexCur = pLevel->iTabCur;
        op = 0;
      }else if( pWInfo->eOnePass!=ONEPASS_OFF ){
        Index *pJ = pTabItem->pTab->pIndex;
        iIndexCur = iAuxArg;
        assert( wctrlFlags & WHERE_ONEPASS_DESIRED );
        while( ALWAYS(pJ) && pJ!=pIx ){
          iIndexCur++;
          pJ = pJ->pNext;
        }
        op = OP_OpenWrite;
        pWInfo->aiCurOnePass[1] = iIndexCur;
      }else if( iAuxArg && (wctrlFlags & WHERE_OR_SUBCLAUSE)!=0 ){
        iIndexCur = iAuxArg;
        op = OP_ReopenIdx;
      }else{
        iIndexCur = pParse->nTab++;
      }
      pLevel->iIdxCur = iIndexCur;
      assert( pIx!=0 );
      assert( pIx->pSchema==pTab->pSchema );
      assert( iIndexCur>=0 );
      if( op ){
        sqlite3VdbeAddOp3(v, op, iIndexCur, pIx->tnum, iDb);
        sqlite3VdbeSetP4KeyInfo(pParse, pIx);
        if( (pLoop->wsFlags & WHERE_CONSTRAINT)!=0
         && (pLoop->wsFlags & (WHERE_COLUMN_RANGE|WHERE_SKIPSCAN))==0
         && (pLoop->wsFlags & WHERE_BIGNULL_SORT)==0
         && (pLoop->wsFlags & WHERE_IN_SEEKSCAN)==0
         && (pWInfo->wctrlFlags&WHERE_ORDERBY_MIN)==0
         && pWInfo->eDistinct!=WHERE_DISTINCT_ORDERED
        ){
          sqlite3VdbeChangeP5(v, OPFLAG_SEEKEQ);
        }
        VdbeComment((v, "%s", pIx->zName));
#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
        {
          u64 colUsed = 0;
          int ii, jj;
          for(ii=0; ii<pIx->nColumn; ii++){
            jj = pIx->aiColumn[ii];
            if( jj<0 ) continue;
            if( jj>63 ) jj = 63;
            if( (pTabItem->colUsed & MASKBIT(jj))==0 ) continue;
            colUsed |= ((u64)1)<<(ii<63 ? ii : 63);
          }
          sqlite3VdbeAddOp4Dup8(v, OP_ColumnsUsed, iIndexCur, 0, 0,
                                (u8*)&colUsed, P4_INT64);
        }
#endif /* SQLITE_ENABLE_COLUMN_USED_MASK */
      }
    }
    if( iDb>=0 ) sqlite3CodeVerifySchema(pParse, iDb);
    if( (pTabItem->fg.jointype & JT_RIGHT)!=0
     && (pLevel->pRJ = sqlite3WhereMalloc(pWInfo, sizeof(WhereRightJoin)))!=0
    ){
      WhereRightJoin *pRJ = pLevel->pRJ;
      pRJ->iMatch = pParse->nTab++;
      pRJ->regBloom = ++pParse->nMem;
      sqlite3VdbeAddOp2(v, OP_Blob, 65536, pRJ->regBloom);
      pRJ->regReturn = ++pParse->nMem;
      sqlite3VdbeAddOp2(v, OP_Null, 0, pRJ->regReturn);
      assert( pTab==pTabItem->pTab );
      if( HasRowid(pTab) ){
        KeyInfo *pInfo;
        sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pRJ->iMatch, 1);
        pInfo = sqlite3KeyInfoAlloc(pParse->db, 1, 0);
        if( pInfo ){
          pInfo->aColl[0] = 0;
          pInfo->aSortFlags[0] = 0;
          sqlite3VdbeAppendP4(v, pInfo, P4_KEYINFO);
        }
      }else{
        Index *pPk = sqlite3PrimaryKeyIndex(pTab);
        sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pRJ->iMatch, pPk->nKeyCol);
        sqlite3VdbeSetP4KeyInfo(pParse, pPk);
      }
      pLoop->wsFlags &= ~WHERE_IDX_ONLY;
      /* The nature of RIGHT JOIN processing is such that it messes up
      ** the output order.  So omit any ORDER BY/GROUP BY elimination
      ** optimizations.  We need to do an actual sort for RIGHT JOIN. */
      pWInfo->nOBSat = 0;
      pWInfo->eDistinct = WHERE_DISTINCT_UNORDERED;
    }
  }
  pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
  if( db->mallocFailed ) goto whereBeginError;

  /* Generate the code to do the search.  Each iteration of the for
  ** loop below generates code for a single nested loop of the VM
  ** program.
  */
  for(ii=0; ii<nTabList; ii++){
    int addrExplain;
    int wsFlags;
    SrcItem *pSrc;
    if( pParse->nErr ) goto whereBeginError;
    pLevel = &pWInfo->a[ii];
    wsFlags = pLevel->pWLoop->wsFlags;
    pSrc = &pTabList->a[pLevel->iFrom];
    if( pSrc->fg.isMaterialized ){
      if( pSrc->fg.isCorrelated ){
        sqlite3VdbeAddOp2(v, OP_Gosub, pSrc->regReturn, pSrc->addrFillSub);
      }else{
        int iOnce = sqlite3VdbeAddOp0(v, OP_Once);  VdbeCoverage(v);
        sqlite3VdbeAddOp2(v, OP_Gosub, pSrc->regReturn, pSrc->addrFillSub);
        sqlite3VdbeJumpHere(v, iOnce);
      }
    }
    if( (wsFlags & (WHERE_AUTO_INDEX|WHERE_BLOOMFILTER))!=0 ){
      if( (wsFlags & WHERE_AUTO_INDEX)!=0 ){
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
        constructAutomaticIndex(pParse, &pWInfo->sWC,
                  &pTabList->a[pLevel->iFrom], notReady, pLevel);
#endif
      }else{
        sqlite3ConstructBloomFilter(pWInfo, ii, pLevel, notReady);
      }
      if( db->mallocFailed ) goto whereBeginError;
    }
    addrExplain = sqlite3WhereExplainOneScan(
        pParse, pTabList, pLevel, wctrlFlags
    );
    pLevel->addrBody = sqlite3VdbeCurrentAddr(v);
    notReady = sqlite3WhereCodeOneLoopStart(pParse,v,pWInfo,ii,pLevel,notReady);
    pWInfo->iContinue = pLevel->addrCont;
    if( (wsFlags&WHERE_MULTI_OR)==0 && (wctrlFlags&WHERE_OR_SUBCLAUSE)==0 ){
      sqlite3WhereAddScanStatus(v, pTabList, pLevel, addrExplain);
    }
  }

  /* Done. */
  VdbeModuleComment((v, "Begin WHERE-core"));
  pWInfo->iEndWhere = sqlite3VdbeCurrentAddr(v);
  return pWInfo;

  /* Jump here if malloc fails */
whereBeginError:
  if( pWInfo ){
    testcase( pWInfo->pExprMods!=0 );
    whereUndoExprMods(pWInfo);
    pParse->nQueryLoop = pWInfo->savedNQueryLoop;
    whereInfoFree(db, pWInfo);
  }
  return 0;
}
Unknown