SQLite

        */
        Select *pSelect = pExpr->x.pSelect;
        ExprList *pEList = pSelect->pEList;

        ExplainQueryPlan((pParse, 1, "%sLIST SUBQUERY",
            jmpIfDynamic>=0?"":"CORRELATED "
        ));
        ExplainQueryPlanSetId(pParse, pSelect);
        assert( !isRowid );
        /* If the LHS and RHS of the IN operator do not match, that
        ** error will have been caught long before we reach this point. */
        if( ALWAYS(pEList->nExpr==nVal) ){
          SelectDest dest;
          int i;
          sqlite3SelectDestInit(&dest, SRT_Set, pExpr->iTable);

      testcase( pExpr->op==TK_SELECT );
      assert( pExpr->op==TK_EXISTS || pExpr->op==TK_SELECT );
      assert( ExprHasProperty(pExpr, EP_xIsSelect) );

      pSel = pExpr->x.pSelect;
      ExplainQueryPlan((pParse, 1, "%sSCALAR SUBQUERY",
            jmpIfDynamic>=0?"":"CORRELATED "));
      ExplainQueryPlanSetId(pParse, pSel);
      nReg = pExpr->op==TK_SELECT ? pSel->pEList->nExpr : 1;
      sqlite3SelectDestInit(&dest, 0, pParse->nMem+1);
      pParse->nMem += nReg;
      if( pExpr->op==TK_SELECT ){
        dest.eDest = SRT_Mem;
        dest.iSdst = dest.iSDParm;
        dest.nSdst = nReg;

  pNew->op = TK_SELECT;
  pNew->selFlags = selFlags;
  pNew->iLimit = 0;
  pNew->iOffset = 0;
#if SELECTTRACE_ENABLED
  pNew->zSelName[0] = 0;
#endif
#if SELECTTRACE_ENABLED || !defined(SQLITE_OMIT_EXPLAIN)
  pNew->iSelectId = 0;
#endif
  pNew->addrOpenEphm[0] = -1;
  pNew->addrOpenEphm[1] = -1;
  pNew->nSelectRow = 0;
  if( pSrc==0 ) pSrc = sqlite3DbMallocZero(pParse->db, sizeof(*pSrc));
  pNew->pSrc = pSrc;
  pNew->pWhere = pWhere;
  pNew->pGroupBy = pGroupBy;

  /* Detach the ORDER BY clause from the compound SELECT */
  p->pOrderBy = 0;

  /* Store the results of the setup-query in Queue. */
  pSetup->pNext = 0;
  ExplainQueryPlan((pParse, 1, "SETUP"));
  ExplainQueryPlanSetId(pParse, pSetup);
  rc = sqlite3Select(pParse, pSetup, &destQueue);
  pSetup->pNext = p;
  if( rc ) goto end_of_recursive_query;

  /* Find the next row in the Queue and output that row */
  addrTop = sqlite3VdbeAddOp2(v, OP_Rewind, iQueue, addrBreak); VdbeCoverage(v);

  ** the value for the recursive-table. Store the results in the Queue.
  */
  if( p->selFlags & SF_Aggregate ){
    sqlite3ErrorMsg(pParse, "recursive aggregate queries not supported");
  }else{
    p->pPrior = 0;
    ExplainQueryPlan((pParse, 1, "RECURSIVE STEP"));
    ExplainQueryPlanSetId(pParse, p);
    sqlite3Select(pParse, p, &destQueue);
    assert( p->pPrior==0 );
    p->pPrior = pSetup;
  }

  /* Keep running the loop until the Queue is empty */
  sqlite3VdbeGoto(v, addrTop);

  /* Compound SELECTs that have an ORDER BY clause are handled separately.
  */
  if( p->pOrderBy ){
    return multiSelectOrderBy(pParse, p, pDest);
  }else{

#ifndef SQLITE_OMIT_EXPLAIN
    if( p->pNext==0 ){
      ExplainQueryPlan((pParse, 1, "COMPOUND QUERY"));
    }
    if( pPrior->pPrior==0 ){
      ExplainQueryPlan((pParse, 1, "LEFT-MOST SUBQUERY"));
      ExplainQueryPlanSetId(pParse, pPrior);
    }
#endif

    /* Generate code for the left and right SELECT statements.
    */
    switch( p->op ){
      case TK_ALL: {

          VdbeComment((v, "Jump ahead if LIMIT reached"));
          if( p->iOffset ){
            sqlite3VdbeAddOp3(v, OP_OffsetLimit,
                              p->iLimit, p->iOffset+1, p->iOffset);
          }
        }
        ExplainQueryPlan((pParse, 1, "UNION ALL"));
        ExplainQueryPlanSetId(pParse, p);
        rc = sqlite3Select(pParse, p, &dest);
        testcase( rc!=SQLITE_OK );
        pDelete = p->pPrior;
        p->pPrior = pPrior;
        p->nSelectRow = sqlite3LogEstAdd(p->nSelectRow, pPrior->nSelectRow);
        if( pPrior->pLimit
         && sqlite3ExprIsInteger(pPrior->pLimit->pLeft, &nLimit)

        }
        p->pPrior = 0;
        pLimit = p->pLimit;
        p->pLimit = 0;
        uniondest.eDest = op;
        ExplainQueryPlan((pParse, 1, "%s USING TEMP B-TREE",
                          selectOpName(p->op)));
        ExplainQueryPlanSetId(pParse, p);
        rc = sqlite3Select(pParse, p, &uniondest);
        testcase( rc!=SQLITE_OK );
        /* Query flattening in sqlite3Select() might refill p->pOrderBy.
        ** Be sure to delete p->pOrderBy, therefore, to avoid a memory leak. */
        sqlite3ExprListDelete(db, p->pOrderBy);
        pDelete = p->pPrior;
        p->pPrior = pPrior;

        p->addrOpenEphm[1] = addr;
        p->pPrior = 0;
        pLimit = p->pLimit;
        p->pLimit = 0;
        intersectdest.iSDParm = tab2;
        ExplainQueryPlan((pParse, 1, "%s USING TEMP B-TREE",
                          selectOpName(p->op)));
        ExplainQueryPlanSetId(pParse, p);
        rc = sqlite3Select(pParse, p, &intersectdest);
        testcase( rc!=SQLITE_OK );
        pDelete = p->pPrior;
        p->pPrior = pPrior;
        if( p->nSelectRow>pPrior->nSelectRow ){
          p->nSelectRow = pPrior->nSelectRow;
        }

  ** left of the compound operator - the "A" select.
  */
  addrSelectA = sqlite3VdbeCurrentAddr(v) + 1;
  addr1 = sqlite3VdbeAddOp3(v, OP_InitCoroutine, regAddrA, 0, addrSelectA);
  VdbeComment((v, "left SELECT"));
  pPrior->iLimit = regLimitA;
  ExplainQueryPlan((pParse, 1, "LEFT"));
  ExplainQueryPlanSetId(pParse, pPrior);
  sqlite3Select(pParse, pPrior, &destA);
  sqlite3VdbeEndCoroutine(v, regAddrA);
  sqlite3VdbeJumpHere(v, addr1);

  /* Generate a coroutine to evaluate the SELECT statement on 
  ** the right - the "B" select
  */
  addrSelectB = sqlite3VdbeCurrentAddr(v) + 1;
  addr1 = sqlite3VdbeAddOp3(v, OP_InitCoroutine, regAddrB, 0, addrSelectB);
  VdbeComment((v, "right SELECT"));
  savedLimit = p->iLimit;
  savedOffset = p->iOffset;
  p->iLimit = regLimitB;
  p->iOffset = 0;  
  ExplainQueryPlan((pParse, 1, "RIGHT"));
  ExplainQueryPlanSetId(pParse, p);
  sqlite3Select(pParse, p, &destB);
  p->iLimit = savedLimit;
  p->iOffset = savedOffset;
  sqlite3VdbeEndCoroutine(v, regAddrB);

  /* Generate a subroutine that outputs the current row of the A
  ** select as the next output row of the compound select.

     
      pItem->regReturn = ++pParse->nMem;
      sqlite3VdbeAddOp3(v, OP_InitCoroutine, pItem->regReturn, 0, addrTop);
      VdbeComment((v, "%s", pItem->pTab->zName));
      pItem->addrFillSub = addrTop;
      sqlite3SelectDestInit(&dest, SRT_Coroutine, pItem->regReturn);
      ExplainQueryPlan((pParse, 1, "CO-ROUTINE 0x%p", pSub));
      ExplainQueryPlanSetId(pParse, pSub);
      sqlite3Select(pParse, pSub, &dest);
      pItem->pTab->nRowLogEst = pSub->nSelectRow;
      pItem->fg.viaCoroutine = 1;
      pItem->regResult = dest.iSdst;
      sqlite3VdbeEndCoroutine(v, pItem->regReturn);
      sqlite3VdbeJumpHere(v, addrTop-1);
      sqlite3ClearTempRegCache(pParse);

      if( pPrior ){
        sqlite3VdbeAddOp2(v, OP_OpenDup, pItem->iCursor, pPrior->iCursor);
        assert( pPrior->pSelect!=0 );
        pSub->nSelectRow = pPrior->pSelect->nSelectRow;
      }else{
        sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
        ExplainQueryPlan((pParse, 1, "MATERIALIZE 0x%p", pSub));
        ExplainQueryPlanSetId(pParse,pSub);
        sqlite3Select(pParse, pSub, &dest);
      }
      pItem->pTab->nRowLogEst = pSub->nSelectRow;
      if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
      retAddr = sqlite3VdbeAddOp1(v, OP_Return, pItem->regReturn);
      VdbeComment((v, "end %s", pItem->pTab->zName));
      sqlite3VdbeChangeP1(v, topAddr, retAddr);

  u8 op;                 /* One of: TK_UNION TK_ALL TK_INTERSECT TK_EXCEPT */
  LogEst nSelectRow;     /* Estimated number of result rows */
  u32 selFlags;          /* Various SF_* values */
  int iLimit, iOffset;   /* Memory registers holding LIMIT & OFFSET counters */
#if SELECTTRACE_ENABLED
  char zSelName[12];     /* Symbolic name of this SELECT use for debugging */
#endif
#if defined(SQLITETRACE_ENABLED) || !defined(SQLITE_OMIT_EXPLAIN)
  u32 iSelectId;         /* EXPLAIN QUERY PLAN select ID */
#endif
  int addrOpenEphm[2];   /* OP_OpenEphem opcodes related to this select */
  SrcList *pSrc;         /* The FROM clause */
  Expr *pWhere;          /* The WHERE clause */
  ExprList *pGroupBy;    /* The GROUP BY clause */
  Expr *pHaving;         /* The HAVING clause */
  ExprList *pOrderBy;    /* The ORDER BY clause */
  Select *pPrior;        /* Prior select in a compound select statement */

    sqlite3TreeViewWith(pView, p->pWith, 1);
    cnt = 1;
    sqlite3TreeViewPush(pView, 1);
  }
  do{
#if SELECTTRACE_ENABLED
    sqlite3TreeViewLine(pView,
      "SELECT%s%s (%s/%d/%p) selFlags=0x%x nSelectRow=%d",
      ((p->selFlags & SF_Distinct) ? " DISTINCT" : ""),
      ((p->selFlags & SF_Aggregate) ? " agg_flag" : ""),
      p->zSelName, p->iSelectId, p, p->selFlags,
      (int)p->nSelectRow
    );
#else
    sqlite3TreeViewLine(pView, "SELECT%s%s (0x%p) selFlags=0x%x nSelectRow=%d",
      ((p->selFlags & SF_Distinct) ? " DISTINCT" : ""),
      ((p->selFlags & SF_Aggregate) ? " agg_flag" : ""), p, p->selFlags,
      (int)p->nSelectRow

#ifndef SQLITE_OMIT_EXPLAIN
  void sqlite3VdbeExplain(Parse*,u8,const char*,...);
  void sqlite3VdbeExplainPop(Parse*);
  int sqlite3VdbeExplainParent(Parse*);
# define ExplainQueryPlan(P)        sqlite3VdbeExplain P
# define ExplainQueryPlanPop(P)     sqlite3VdbeExplainPop(P)
# define ExplainQueryPlanParent(P)  sqlite3VdbeExplainParent(P)
# define ExplainQueryPlanSetId(P,S) (S)->iSelectId=(P)->addrExplain
#else
# define ExplainQueryPlan(P)
# define ExplainQueryPlanPop(P)
# define ExplainQueryPlanParent(P) 0
# define ExplainQueryPlanSetId(P,S)
#endif
void sqlite3VdbeAddParseSchemaOp(Vdbe*,int,char*);
void sqlite3VdbeChangeOpcode(Vdbe*, u32 addr, u8);
void sqlite3VdbeChangeP1(Vdbe*, u32 addr, int P1);
void sqlite3VdbeChangeP2(Vdbe*, u32 addr, int P2);
void sqlite3VdbeChangeP3(Vdbe*, u32 addr, int P3);
void sqlite3VdbeChangeP5(Vdbe*, u16 P5);