SQLite

  pNew->iOffset = 0;
  pNew->selFlags = p->selFlags & ~SF_UsesEphemeral;
  pNew->pRightmost = 0;
  pNew->addrOpenEphm[0] = -1;
  pNew->addrOpenEphm[1] = -1;
  pNew->addrOpenEphm[2] = -1;
  pNew->pWith = withDup(db, p->pWith);
  pNew->pRecurse = p->pRecurse;
  return pNew;
}
#else
Select *sqlite3SelectDup(sqlite3 *db, Select *p, int flags){
  assert( p==0 );
  return 0;
}

  int iSub2;            /* EQP id of right-hand query */
#endif

  /* Make sure there is no ORDER BY or LIMIT clause on prior SELECTs.  Only
  ** the last (right-most) SELECT in the series may have an ORDER BY or LIMIT.
  */
  assert( p && p->pPrior );  /* Calling function guarantees this much */
  assert( p->pRecurse==0 || p->op==TK_ALL || p->op==TK_UNION );
  db = pParse->db;
  pPrior = p->pPrior;
  assert( pPrior->pRightmost!=pPrior );
  assert( pPrior->pRightmost==p->pRightmost );
  dest = *pDest;
  if( pPrior->pOrderBy ){
    sqlite3ErrorMsg(pParse,"ORDER BY clause should come after %s not before",

    goto multi_select_end;
  }

#ifndef SQLITE_OMIT_CTE
  /* If this is a recursive query, check that there is no ORDER BY or
  ** LIMIT clause. Neither of these are supported.  */
  assert( p->pOffset==0 || p->pLimit );
  if( p->pRecurse && (p->pOrderBy || p->pLimit) ){
    sqlite3ErrorMsg(pParse, "%s in a recursive query is not allowed",
        p->pOrderBy ? "ORDER BY" : "LIMIT"
    );
    goto multi_select_end;
  }

  if( p->pRecurse ){

    int nCol = p->pEList->nExpr;
    int addrNext;
    int addrSwap;
    int iCont, iBreak;

    int tmp1, tmp2;               /* Cursors used to access temporary tables */
    int tmp3 = 0;                 /* To ensure unique results if UNION */
    int eDest = SRT_Table;
    SelectDest tmp2dest;


    iBreak = sqlite3VdbeMakeLabel(v);
    iCont = sqlite3VdbeMakeLabel(v);



    tmp1 = pParse->nTab++;




    tmp2 = pParse->nTab++;
    if( p->op==TK_UNION ){
      eDest = SRT_DistTable;
      tmp3 = pParse->nTab++;
    }
    sqlite3SelectDestInit(&tmp2dest, eDest, tmp2);

    sqlite3VdbeResolveLabel(v, iCont);
    sqlite3VdbeAddOp2(v, OP_Next, tmp1, addrNext);

    /* Execute the recursive SELECT. Store the results in tmp2. While this
    ** SELECT is running, the contents of tmp1 are read by recursive 
    ** references to the current CTE.  */
    p->pPrior = 0;
    p->pRecurse->tnum = tmp1;
    assert( (p->pRecurse->tabFlags & TF_Recursive)==0 );
    p->pRecurse->tabFlags |= TF_Recursive;
    rc = sqlite3Select(pParse, p, &tmp2dest);
    p->pRecurse->tabFlags &= ~TF_Recursive;
    assert( p->pPrior==0 );
    p->pPrior = pPrior;
    if( rc ) goto multi_select_end;

    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrSwap);
    sqlite3VdbeResolveLabel(v, iBreak);
  }else

     return 0;                                           /* Restriction (11) */
  }
  if( isAgg && pSub->pOrderBy ) return 0;                /* Restriction (16) */
  if( pSub->pLimit && p->pWhere ) return 0;              /* Restriction (19) */
  if( pSub->pLimit && (p->selFlags & SF_Distinct)!=0 ){
     return 0;         /* Restriction (21) */
  }
  if( pSub->pRecurse ) return 0;                         /* Restriction (22)  */
  if( p->pRecurse && pSub->pPrior ) return 0;            /* Restriction (23)  */

  /* OBSOLETE COMMENT 1:
  ** Restriction 3:  If the subquery is a join, make sure the subquery is 
  ** not used as the right operand of an outer join.  Examples of why this
  ** is not allowed:
  **
  **         t1 LEFT OUTER JOIN (t2 JOIN t3)

  Parse *pParse = pWalker->pParse;
  sqlite3 *db = pParse->db;
  struct Cte *pCte;

  assert( pFrom->pTab==0 );

  pCte = searchWith(pParse->pWith, pFrom);
  if( pCte==0 ){
    /* no-op */
  }else if( pCte==pParse->pCte && (pTab = pCte->pTab) ){
    /* This is the recursive part of a recursive CTE */
    assert( pFrom->pTab==0 && pFrom->isRecursive==0 && pFrom->pSelect==0 );
    pFrom->pTab = pTab;
    pFrom->isRecursive = 1;
    pTab->nRef++;
  }else{
    ExprList *pEList;
    Select *pSel;
    Select *pLeft;                /* Left-most SELECT statement */
    int bRecursive;

    pFrom->pTab = pTab = sqlite3DbMallocZero(db, sizeof(Table));
    if( pTab==0 ) return WRC_Abort;
    pTab->nRef = 1;
    pTab->zName = sqlite3MPrintf(db, "%s", pCte->zName);
    pTab->iPKey = -1;
    pTab->nRowEst = 1048576;
    pTab->tabFlags |= TF_Ephemeral;
    pFrom->pSelect = sqlite3SelectDup(db, pCte->pSelect, 0);
    if( db->mallocFailed ) return SQLITE_NOMEM;
    assert( pFrom->pSelect );

    if( ctePush(pParse, pCte) ) return WRC_Abort;
    pSel = pFrom->pSelect;
    bRecursive = (pSel->op==TK_ALL || pSel->op==TK_UNION);









    if( bRecursive ){
      assert( pSel->pPrior );
      sqlite3WalkSelect(pWalker, pSel->pPrior);



    }else{


      sqlite3WalkSelect(pWalker, pSel);



    }





    for(pLeft=pSel; pLeft->pPrior; pLeft=pLeft->pPrior);
    pEList = pLeft->pEList;
    if( pCte->pCols ){
      if( pEList->nExpr!=pCte->pCols->nExpr ){
        sqlite3ErrorMsg(pParse, "cte \"%s\" returns %d values for %d columns",
            pCte->zName, pEList->nExpr, pCte->pCols->nExpr
        );
        return WRC_Abort;
      }
      pEList = pCte->pCols;
    }

    selectColumnsFromExprList(pParse, pEList, &pTab->nCol, &pTab->aCol);

    if( bRecursive ){
      int nRef = pTab->nRef;
      pCte->pTab = pTab;
      sqlite3WalkSelect(pWalker, pSel);
      pCte->pTab = 0;
      if( pTab->nRef > nRef){
        pSel->pRecurse = pTab;
        assert( pTab->tnum==0 );
      }
    }

    ctePop(pParse, pCte);
  }

  return SQLITE_OK;
}
#endif

  /* Look up every table named in the FROM clause of the select.  If
  ** an entry of the FROM clause is a subquery instead of a table or view,
  ** then create a transient table structure to describe the subquery.
  */
  for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
    Table *pTab;


    if( pFrom->pTab!=0 ){
      /* This statement has already been prepared.  There is no need
      ** to go further. */
      assert( i==0 );
      return WRC_Prune;
    }
#ifndef SQLITE_OMIT_CTE

** enough information about the compound query is known at that point.
** The KeyInfo for addrOpenTran[0] and [1] contains collating sequences
** for the result set.  The KeyInfo for addrOpenEphm[2] contains collating
** sequences for the ORDER BY clause.
*/
struct Select {
  ExprList *pEList;      /* The fields of the result */
  Table *pRecurse;       /* Non-NULL for the recursive part of recursive CTE */
  u8 op;                 /* One of: TK_UNION TK_ALL TK_INTERSECT TK_EXCEPT */
  u16 selFlags;          /* Various SF_* values */
  int iLimit, iOffset;   /* Memory registers holding LIMIT & OFFSET counters */
  int addrOpenEphm[3];   /* OP_OpenEphem opcodes related to this select */
  u64 nSelectRow;        /* Estimated number of result rows */
  SrcList *pSrc;         /* The FROM clause */
  Expr *pWhere;          /* The WHERE clause */

#define SF_Expanded        0x0010  /* sqlite3SelectExpand() called on this */
#define SF_HasTypeInfo     0x0020  /* FROM subqueries have Table metadata */
#define SF_UseSorter       0x0040  /* Sort using a sorter */
#define SF_Values          0x0080  /* Synthesized from VALUES clause */
#define SF_Materialize     0x0100  /* Force materialization of views */
#define SF_NestedFrom      0x0200  /* Part of a parenthesized FROM clause */
#define SF_MaybeConvert    0x0400  /* Need convertCompoundSelectToSubquery() */



/*
** The results of a select can be distributed in several ways.  The
** "SRT" prefix means "SELECT Result Type".
*/
#define SRT_Union        1  /* Store result as keys in an index */

** callbacks.
*/
#define WRC_Continue    0   /* Continue down into children */
#define WRC_Prune       1   /* Omit children but continue walking siblings */
#define WRC_Abort       2   /* Abandon the tree walk */

/*
** An instance of this structure represents a set of on or more CTEs
** (common table expressions) created by a single WITH clause.
*/
struct With {
  int nCte;                       /* Number of CTEs in the WITH clause */
  With *pOuter;                   /* Containing WITH clause, or NULL */
  struct Cte {                    /* For each CTE in the WITH clause.... */
    char *zName;                    /* Name of this CTE */
    ExprList *pCols;                /* List of explicit column names, or NULL */
    Select *pSelect;                /* The definition of this CTE */
    struct Cte *pOuterCte;          /* Next WITH clause in outer context */
    Table *pTab;                    /* Table object for this CTE */
  } a[1];
};

/*
** Assuming zIn points to the first byte of a UTF-8 character,
** advance zIn to point to the first byte of the next UTF-8 character.
*/

    }
  }
  pCx->isOrdered = (pOp->p5!=BTREE_UNORDERED);
  break;
}

#ifndef SQLITE_OMIT_CTE
/* Opcode: OpenEphreader P1 P2 * * *
**
** P2 is a cursor opened by the OpenEphemeral opcode. This opcode opens
** a new read-only cursor named P1 that accesses the same epheremal table 
** as P2.
*/
case OP_OpenEphreader: {
  VdbeCursor *pEph;
  VdbeCursor *pCx;
  Pgno pgno;

  pEph = p->apCsr[pOp->p2];
  pCx = allocateCursor(p, pOp->p1, pEph->nField, -1, 1);
  if( pCx==0 ) goto no_mem;
  pCx->nullRow = 1;
  pCx->pKeyInfo = pEph->pKeyInfo;
  pCx->isTable = pEph->isTable;
  pCx->isOrdered = pEph->isOrdered;
  pgno = MASTER_ROOT + !pCx->isTable;
  rc = sqlite3BtreeCursor(pEph->pBt, pgno, 0, pCx->pKeyInfo, pCx->pCursor);
  break;
}

/* Opcode: SwapCursors P1 P2 * * *
**
** Parameters P1 and P2 are both cursors opened by the OpenEphemeral
** opcode. This opcode deletes the contents of epheremal table P1,
** then renames P2 to P1 and P1 to P2. In other words, following this
** opcode cursor P2 is open on an empty table and P1 is open on the
** table that was initially accessed by P2.

    struct SrcList_item *pTabItem;

    pTabItem = &pTabList->a[pLevel->iFrom];
    pTab = pTabItem->pTab;
    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
    pLoop = pLevel->pWLoop;
    if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
#ifndef SQLITE_OMIT_CTE
      if( pTab->tabFlags & TF_Recursive ){
        int iCur = pTabItem->iCursor;
        sqlite3VdbeAddOp2(v, OP_OpenEphreader, iCur, pTab->tnum);
      }
#endif
      /* Otherwise 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) ){