SQLite

    ** a no-op).  */
    invalidateIncrblobCursors(p, 0, 1);
    rc = clearDatabasePage(pBt, (Pgno)iTable, 0, pnChange);
  }
  sqlite3BtreeLeave(p);
  return rc;
}

/*
** Delete all information from the single table that pCur is open on.
**
** This routine only work for pCur on an ephemeral table.
*/
int sqlite3BtreeClearTableOfCursor(BtCursor *pCur){
  return sqlite3BtreeClearTable(pCur->pBtree, pCur->pgnoRoot, 0);
}

/*
** Erase all information in a table and add the root of the table to
** the freelist.  Except, the root of the principle table (the one on
** page 1) is never added to the freelist.
**
** This routine will fail with SQLITE_LOCKED if there are any open

** indices.)
*/
#define BTREE_INTKEY     1    /* Table has only 64-bit signed integer keys */
#define BTREE_BLOBKEY    2    /* Table has keys only - no data */

int sqlite3BtreeDropTable(Btree*, int, int*);
int sqlite3BtreeClearTable(Btree*, int, int*);
int sqlite3BtreeClearTableOfCursor(BtCursor*);
void sqlite3BtreeTripAllCursors(Btree*, int);

void sqlite3BtreeGetMeta(Btree *pBtree, int idx, u32 *pValue);
int sqlite3BtreeUpdateMeta(Btree*, int idx, u32 value);

int sqlite3BtreeNewDb(Btree *p);

ExprList *sqlite3ExprListDup(sqlite3 *db, ExprList *p, int flags){
  ExprList *pNew;
  struct ExprList_item *pItem, *pOldItem;
  int i;
  if( p==0 ) return 0;
  pNew = sqlite3DbMallocRaw(db, sizeof(*pNew) );
  if( pNew==0 ) return 0;

  pNew->nExpr = i = p->nExpr;
  if( (flags & EXPRDUP_REDUCE)==0 ) for(i=1; i<p->nExpr; i+=i){}
  pNew->a = pItem = sqlite3DbMallocRaw(db,  i*sizeof(p->a[0]) );
  if( pItem==0 ){
    sqlite3DbFree(db, pNew);
    return 0;
  } 

  pNew->pLimit = sqlite3ExprDup(db, p->pLimit, flags);
  pNew->pOffset = sqlite3ExprDup(db, p->pOffset, flags);
  pNew->iLimit = 0;
  pNew->iOffset = 0;
  pNew->selFlags = p->selFlags & ~SF_UsesEphemeral;
  pNew->addrOpenEphm[0] = -1;
  pNew->addrOpenEphm[1] = -1;

  pNew->nSelectRow = p->nSelectRow;
  pNew->pWith = withDup(db, p->pWith);
  return pNew;
}
#else
Select *sqlite3SelectDup(sqlite3 *db, Select *p, int flags){
  assert( p==0 );

** Generate code to move content from registers iFrom...iFrom+nReg-1
** over to iTo..iTo+nReg-1. Keep the column cache up-to-date.
*/
void sqlite3ExprCodeMove(Parse *pParse, int iFrom, int iTo, int nReg){
  int i;
  struct yColCache *p;
  assert( iFrom>=iTo+nReg || iFrom+nReg<=iTo );
  sqlite3VdbeAddOp3(pParse->pVdbe, OP_Move, iFrom, iTo, nReg);
  for(i=0, p=pParse->aColCache; i<SQLITE_N_COLCACHE; i++, p++){
    int x = p->iReg;
    if( x>=iFrom && x<iFrom+nReg ){
      p->iReg += iTo-iFrom;
    }
  }
}

      /* Do the b-tree integrity checks */
      sqlite3VdbeAddOp3(v, OP_IntegrityCk, 2, cnt, 1);
      sqlite3VdbeChangeP5(v, (u8)i);
      addr = sqlite3VdbeAddOp1(v, OP_IsNull, 2); VdbeCoverage(v);
      sqlite3VdbeAddOp4(v, OP_String8, 0, 3, 0,
         sqlite3MPrintf(db, "*** in database %s ***\n", db->aDb[i].zName),
         P4_DYNAMIC);
      sqlite3VdbeAddOp3(v, OP_Move, 2, 4, 1);
      sqlite3VdbeAddOp3(v, OP_Concat, 4, 3, 2);
      sqlite3VdbeAddOp2(v, OP_ResultRow, 2, 1);
      sqlite3VdbeJumpHere(v, addr);

      /* Make sure all the indices are constructed correctly.
      */
      for(x=sqliteHashFirst(pTbls); x && !isQuick; x=sqliteHashNext(x)){

**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
*/
#include "sqliteInt.h"

/*
** An instance of the following object is used to record information about
** how to process the DISTINCT keyword, to simplify passing that information
** into the selectInnerLoop() routine.
*/
typedef struct DistinctCtx DistinctCtx;
struct DistinctCtx {
  u8 isTnct;      /* True if the DISTINCT keyword is present */
  u8 eTnctType;   /* One of the WHERE_DISTINCT_* operators */
  int tabTnct;    /* Ephemeral table used for DISTINCT processing */
  int addrTnct;   /* Address of OP_OpenEphemeral opcode for tabTnct */
};

/*
** An instance of the following object is used to record information about
** the ORDER BY (or GROUP BY) clause of query is being coded.
*/
typedef struct SortCtx SortCtx;
struct SortCtx {
  ExprList *pOrderBy;   /* The ORDER BY (or GROUP BY clause) */
  int nOBSat;           /* Number of ORDER BY terms satisfied by indices */
  int iECursor;         /* Cursor number for the sorter */
  int regReturn;        /* Register holding block-output return address */
  int labelBkOut;       /* Start label for the block-output subroutine */
  int addrSortIndex;    /* Address of the OP_SorterOpen or OP_OpenEphemeral */
  u8 sortFlags;         /* Zero or more SORTFLAG_* bits */
};
#define SORTFLAG_UseSorter  0x01   /* Use SorterOpen instead of OpenEphemeral */

/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.
*/
static void clearSelect(sqlite3 *db, Select *p){
  sqlite3ExprListDelete(db, p->pEList);

  pNew->selFlags = selFlags;
  pNew->op = TK_SELECT;
  pNew->pLimit = pLimit;
  pNew->pOffset = pOffset;
  assert( pOffset==0 || pLimit!=0 );
  pNew->addrOpenEphm[0] = -1;
  pNew->addrOpenEphm[1] = -1;

  if( db->mallocFailed ) {
    clearSelect(db, pNew);
    if( pNew!=&standin ) sqlite3DbFree(db, pNew);
    pNew = 0;
  }else{
    assert( pNew->pSrc!=0 || pParse->nErr>0 );
  }

                     isOuter, &p->pWhere);
      }
    }
  }
  return 0;
}

/* Forward reference */
static KeyInfo *keyInfoFromExprList(
  Parse *pParse,       /* Parsing context */
  ExprList *pList,     /* Form the KeyInfo object from this ExprList */
  int iStart,          /* Begin with this column of pList */
  int nExtra           /* Add this many extra columns to the end */
);

/*
** Insert code into "v" that will push the record in register regData
** into the sorter.
*/
static void pushOntoSorter(
  Parse *pParse,         /* Parser context */
  SortCtx *pSort,        /* Information about the ORDER BY clause */
  Select *pSelect,       /* The whole SELECT statement */
  int regData            /* Register holding data to be sorted */
){
  Vdbe *v = pParse->pVdbe;
  int nExpr = pSort->pOrderBy->nExpr;
  int regBase = sqlite3GetTempRange(pParse, nExpr+2);
  int regRecord = sqlite3GetTempReg(pParse);
  int nOBSat = pSort->nOBSat;
  int op;
  sqlite3ExprCacheClear(pParse);
  sqlite3ExprCodeExprList(pParse, pSort->pOrderBy, regBase, 0);
  sqlite3VdbeAddOp2(v, OP_Sequence, pSort->iECursor, regBase+nExpr);
  sqlite3ExprCodeMove(pParse, regData, regBase+nExpr+1, 1);
  sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase+nOBSat, nExpr+2-nOBSat, regRecord);
  if( nOBSat>0 ){
    int regPrevKey;   /* The first nOBSat columns of the previous row */
    int addrFirst;    /* Address of the OP_IfNot opcode */
    int addrJmp;      /* Address of the OP_Jump opcode */
    VdbeOp *pOp;      /* Opcode that opens the sorter */
    int nKey;         /* Number of sorting key columns, including OP_Sequence */

    addrFirst = sqlite3VdbeAddOp1(v, OP_IfNot, regBase+nExpr); VdbeCoverage(v);
    pOp = sqlite3VdbeGetOp(v, pSort->addrSortIndex);
    pOp->opcode = OP_OpenEphemeral;
    pSort->sortFlags &= ~SORTFLAG_UseSorter;
    nKey = nExpr - pSort->nOBSat + 1;
    pOp->p2 = nKey + 1;
    regPrevKey = pParse->nMem+1;
    pParse->nMem += pSort->nOBSat;
    sqlite3VdbeAddOp4(v, OP_Compare, regPrevKey, regBase, pSort->nOBSat,
                      (char*)pOp->p4.pKeyInfo, P4_KEYINFO);
    pOp->p4.pKeyInfo = keyInfoFromExprList(pParse, pSort->pOrderBy, nOBSat, 1);
    addrJmp = sqlite3VdbeCurrentAddr(v);
    sqlite3VdbeAddOp3(v, OP_Jump, addrJmp+1, 0, addrJmp+1); VdbeCoverage(v);
    pSort->labelBkOut = sqlite3VdbeMakeLabel(v);
    pSort->regReturn = ++pParse->nMem;
    sqlite3VdbeAddOp2(v, OP_Gosub, pSort->regReturn, pSort->labelBkOut);
    sqlite3VdbeAddOp1(v, OP_ClearEphem, pSort->iECursor);
    sqlite3VdbeJumpHere(v, addrFirst);
    sqlite3VdbeAddOp3(v, OP_Move, regBase, regPrevKey, pSort->nOBSat);
    sqlite3VdbeJumpHere(v, addrJmp);
  }
  if( pSort->sortFlags & SORTFLAG_UseSorter ){
    op = OP_SorterInsert;
  }else{
    op = OP_IdxInsert;
  }
  sqlite3VdbeAddOp2(v, op, pSort->iECursor, regRecord);
  sqlite3ReleaseTempReg(pParse, regRecord);
  sqlite3ReleaseTempRange(pParse, regBase, nExpr+2);
  if( pSelect->iLimit ){
    int addr1, addr2;
    int iLimit;
    if( pSelect->iOffset ){
      iLimit = pSelect->iOffset+1;
    }else{
      iLimit = pSelect->iLimit;
    }
    addr1 = sqlite3VdbeAddOp1(v, OP_IfZero, iLimit); VdbeCoverage(v);
    sqlite3VdbeAddOp2(v, OP_AddImm, iLimit, -1);
    addr2 = sqlite3VdbeAddOp0(v, OP_Goto);
    sqlite3VdbeJumpHere(v, addr1);
    sqlite3VdbeAddOp1(v, OP_Last, pSort->iECursor);
    sqlite3VdbeAddOp1(v, OP_Delete, pSort->iECursor);
    sqlite3VdbeJumpHere(v, addr2);
  }
}

/*
** Add code to implement the OFFSET
*/

    return 1;
  }else{
    return 0;
  }
}
#endif














/*
** This routine generates the code for the inside of the inner loop
** of a SELECT.
**
** If srcTab is negative, then the pEList expressions
** are evaluated in order to get the data for this row.  If srcTab is
** zero or more, then data is pulled from srcTab and pEList is used only 
** to get number columns and the datatype for each column.
*/
static void selectInnerLoop(
  Parse *pParse,          /* The parser context */
  Select *p,              /* The complete select statement being coded */
  ExprList *pEList,       /* List of values being extracted */
  int srcTab,             /* Pull data from this table */
  SortCtx *pSort,         /* If not NULL, info on how to process ORDER BY */

  DistinctCtx *pDistinct, /* If not NULL, info on how to process DISTINCT */
  SelectDest *pDest,      /* How to dispose of the results */
  int iContinue,          /* Jump here to continue with next row */
  int iBreak              /* Jump here to break out of the inner loop */
){
  Vdbe *v = pParse->pVdbe;
  int i;
  int hasDistinct;        /* True if the DISTINCT keyword is present */
  int regResult;              /* Start of memory holding result set */
  int eDest = pDest->eDest;   /* How to dispose of results */
  int iParm = pDest->iSDParm; /* First argument to disposal method */
  int nResultCol;             /* Number of result columns */

  assert( v );
  assert( pEList!=0 );
  hasDistinct = pDistinct ? pDistinct->eTnctType : WHERE_DISTINCT_NOOP;
  if( pSort && pSort->pOrderBy==0 ) pSort = 0;
  if( pSort==0 && !hasDistinct ){
    codeOffset(v, p->iOffset, iContinue);
  }

  /* Pull the requested columns.
  */
  nResultCol = pEList->nExpr;

      default: {
        assert( pDistinct->eTnctType==WHERE_DISTINCT_UNORDERED );
        codeDistinct(pParse, pDistinct->tabTnct, iContinue, nResultCol, regResult);
        break;
      }
    }
    if( pSort==0 ){
      codeOffset(v, p->iOffset, iContinue);
    }
  }

  switch( eDest ){
    /* In this mode, write each query result to the key of the temporary
    ** table iParm.

        ** on an ephemeral index. If the current row is already present
        ** in the index, do not write it to the output. If not, add the
        ** current row to the index and proceed with writing it to the
        ** output table as well.  */
        int addr = sqlite3VdbeCurrentAddr(v) + 4;
        sqlite3VdbeAddOp4Int(v, OP_Found, iParm+1, addr, r1, 0); VdbeCoverage(v);
        sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm+1, r1);
        assert( pSort==0 );
      }
#endif
      if( pSort ){
        pushOntoSorter(pParse, pSort, p, r1);
      }else{
        int r2 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, r2);
        sqlite3VdbeAddOp3(v, OP_Insert, iParm, r1, r2);
        sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
        sqlite3ReleaseTempReg(pParse, r2);
      }
      sqlite3ReleaseTempReg(pParse, r1);
      break;
    }

#ifndef SQLITE_OMIT_SUBQUERY
    /* If we are creating a set for an "expr IN (SELECT ...)" construct,
    ** then there should be a single item on the stack.  Write this
    ** item into the set table with bogus data.
    */
    case SRT_Set: {
      assert( nResultCol==1 );
      pDest->affSdst =
                  sqlite3CompareAffinity(pEList->a[0].pExpr, pDest->affSdst);
      if( pSort ){
        /* At first glance you would think we could optimize out the
        ** ORDER BY in this case since the order of entries in the set
        ** does not matter.  But there might be a LIMIT clause, in which
        ** case the order does matter */
        pushOntoSorter(pParse, pSort, p, regResult);
      }else{
        int r1 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp4(v, OP_MakeRecord, regResult,1,r1, &pDest->affSdst, 1);
        sqlite3ExprCacheAffinityChange(pParse, regResult, 1);
        sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
        sqlite3ReleaseTempReg(pParse, r1);
      }

    /* If this is a scalar select that is part of an expression, then
    ** store the results in the appropriate memory cell and break out
    ** of the scan loop.
    */
    case SRT_Mem: {
      assert( nResultCol==1 );
      if( pSort ){
        pushOntoSorter(pParse, pSort, p, regResult);
      }else{
        sqlite3ExprCodeMove(pParse, regResult, iParm, 1);
        /* The LIMIT clause will jump out of the loop for us */
      }
      break;
    }
#endif /* #ifndef SQLITE_OMIT_SUBQUERY */

    case SRT_Coroutine:       /* Send data to a co-routine */
    case SRT_Output: {        /* Return the results */
      testcase( eDest==SRT_Coroutine );
      testcase( eDest==SRT_Output );
      if( pSort ){
        int r1 = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nResultCol, r1);
        pushOntoSorter(pParse, pSort, p, r1);
        sqlite3ReleaseTempReg(pParse, r1);
      }else if( eDest==SRT_Coroutine ){
        sqlite3VdbeAddOp1(v, OP_Yield, pDest->iSDParm);
      }else{
        sqlite3VdbeAddOp2(v, OP_ResultRow, regResult, nResultCol);
        sqlite3ExprCacheAffinityChange(pParse, regResult, nResultCol);
      }

#endif
  }

  /* Jump to the end of the loop if the LIMIT is reached.  Except, if
  ** there is a sorter, in which case the sorter has already limited
  ** the output for us.
  */
  if( pSort==0 && p->iLimit ){
    sqlite3VdbeAddOp3(v, OP_IfZero, p->iLimit, iBreak, -1); VdbeCoverage(v);
  }
}

/*
** Allocate a KeyInfo object sufficient for an index of N key columns and
** X extra columns.

** then the KeyInfo structure is appropriate for initializing a virtual
** index to implement a DISTINCT test.
**
** Space to hold the KeyInfo structure is obtain from malloc.  The calling
** function is responsible for seeing that this structure is eventually
** freed.
*/
static KeyInfo *keyInfoFromExprList(
  Parse *pParse,       /* Parsing context */
  ExprList *pList,     /* Form the KeyInfo object from this ExprList */
  int iStart,          /* Begin with this column of pList */
  int nExtra           /* Add this many extra columns to the end */
){
  int nExpr;
  KeyInfo *pInfo;
  struct ExprList_item *pItem;
  sqlite3 *db = pParse->db;
  int i;

  nExpr = pList->nExpr;
  pInfo = sqlite3KeyInfoAlloc(db, nExpr+nExtra-iStart, 1);
  if( pInfo ){
    assert( sqlite3KeyInfoIsWriteable(pInfo) );
    for(i=iStart, pItem=pList->a; i<nExpr; i++, pItem++){
      CollSeq *pColl;
      pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
      if( !pColl ) pColl = db->pDfltColl;
      pInfo->aColl[i] = pColl;
      pInfo->aSortOrder[i] = pItem->sortOrder;
    }
  }

** then the results were placed in a sorter.  After the loop is terminated
** we need to run the sorter and output the results.  The following
** routine generates the code needed to do that.
*/
static void generateSortTail(
  Parse *pParse,    /* Parsing context */
  Select *p,        /* The SELECT statement */
  SortCtx *pSort,   /* Information on the ORDER BY clause */
  int nColumn,      /* Number of columns of data */
  SelectDest *pDest /* Write the sorted results here */
){
  Vdbe *v = pParse->pVdbe;                     /* The prepared statement */
  int addrBreak = sqlite3VdbeMakeLabel(v);     /* Jump here to exit loop */
  int addrContinue = sqlite3VdbeMakeLabel(v);  /* Jump here for next cycle */
  int addr;
  int addrOnce = 0;
  int iTab;
  int pseudoTab = 0;
  ExprList *pOrderBy = pSort->pOrderBy;

  int eDest = pDest->eDest;
  int iParm = pDest->iSDParm;

  int regRow;
  int regRowid;
  int nKey;

  if( pSort->labelBkOut ){
    sqlite3VdbeAddOp2(v, OP_Gosub, pSort->regReturn, pSort->labelBkOut);
    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrBreak);
    sqlite3VdbeResolveLabel(v, pSort->labelBkOut);
    addrOnce = sqlite3CodeOnce(pParse); VdbeCoverage(v);
  }
  iTab = pSort->iECursor;
  regRow = sqlite3GetTempReg(pParse);
  if( eDest==SRT_Output || eDest==SRT_Coroutine ){
    pseudoTab = pParse->nTab++;
    sqlite3VdbeAddOp3(v, OP_OpenPseudo, pseudoTab, regRow, nColumn);
    regRowid = 0;
  }else{
    regRowid = sqlite3GetTempReg(pParse);
  }
  nKey = pOrderBy->nExpr - pSort->nOBSat;
  if( pSort->sortFlags & SORTFLAG_UseSorter ){
    int regSortOut = ++pParse->nMem;
    int ptab2 = pParse->nTab++;
    sqlite3VdbeAddOp3(v, OP_OpenPseudo, ptab2, regSortOut, nKey+2);
    if( addrOnce ) sqlite3VdbeJumpHere(v, addrOnce);
    addr = 1 + sqlite3VdbeAddOp2(v, OP_SorterSort, iTab, addrBreak);
    VdbeCoverage(v);
    codeOffset(v, p->iOffset, addrContinue);
    sqlite3VdbeAddOp2(v, OP_SorterData, iTab, regSortOut);
    sqlite3VdbeAddOp3(v, OP_Column, ptab2, nKey+1, regRow);
    sqlite3VdbeChangeP5(v, OPFLAG_CLEARCACHE);
  }else{
    if( addrOnce ) sqlite3VdbeJumpHere(v, addrOnce);
    addr = 1 + sqlite3VdbeAddOp2(v, OP_Sort, iTab, addrBreak); VdbeCoverage(v);
    codeOffset(v, p->iOffset, addrContinue);
    sqlite3VdbeAddOp3(v, OP_Column, iTab, nKey+1, regRow);
  }
  switch( eDest ){
    case SRT_Table:
    case SRT_EphemTab: {
      testcase( eDest==SRT_Table );
      testcase( eDest==SRT_EphemTab );
      sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, regRowid);

  }
  sqlite3ReleaseTempReg(pParse, regRow);
  sqlite3ReleaseTempReg(pParse, regRowid);

  /* The bottom of the loop
  */
  sqlite3VdbeResolveLabel(v, addrContinue);
  if( pSort->sortFlags & SORTFLAG_UseSorter ){
    sqlite3VdbeAddOp2(v, OP_SorterNext, iTab, addr); VdbeCoverage(v);
  }else{
    sqlite3VdbeAddOp2(v, OP_Next, iTab, addr); VdbeCoverage(v);
  }
  if( pSort->regReturn ) sqlite3VdbeAddOp1(v, OP_Return, pSort->regReturn);
  sqlite3VdbeResolveLabel(v, addrBreak);
  if( eDest==SRT_Output || eDest==SRT_Coroutine ){
    sqlite3VdbeAddOp2(v, OP_Close, pseudoTab, 0);
  }
}

/*

  }
  sqlite3VdbeAddOp1(v, OP_Delete, iQueue);

  /* Output the single row in Current */
  addrCont = sqlite3VdbeMakeLabel(v);
  codeOffset(v, regOffset, addrCont);
  selectInnerLoop(pParse, p, p->pEList, iCurrent,
      0, 0, pDest, addrCont, addrBreak);
  if( regLimit ){
    sqlite3VdbeAddOp3(v, OP_IfZero, regLimit, addrBreak, -1);
    VdbeCoverage(v);
  }
  sqlite3VdbeResolveLabel(v, addrCont);

  /* Execute the recursive SELECT taking the single row in Current as

        }
        iBreak = sqlite3VdbeMakeLabel(v);
        iCont = sqlite3VdbeMakeLabel(v);
        computeLimitRegisters(pParse, p, iBreak);
        sqlite3VdbeAddOp2(v, OP_Rewind, unionTab, iBreak); VdbeCoverage(v);
        iStart = sqlite3VdbeCurrentAddr(v);
        selectInnerLoop(pParse, p, p->pEList, unionTab,
                        0, 0, &dest, iCont, iBreak);
        sqlite3VdbeResolveLabel(v, iCont);
        sqlite3VdbeAddOp2(v, OP_Next, unionTab, iStart); VdbeCoverage(v);
        sqlite3VdbeResolveLabel(v, iBreak);
        sqlite3VdbeAddOp2(v, OP_Close, unionTab, 0);
      }
      break;
    }

      computeLimitRegisters(pParse, p, iBreak);
      sqlite3VdbeAddOp2(v, OP_Rewind, tab1, iBreak); VdbeCoverage(v);
      r1 = sqlite3GetTempReg(pParse);
      iStart = sqlite3VdbeAddOp2(v, OP_RowKey, tab1, r1);
      sqlite3VdbeAddOp4Int(v, OP_NotFound, tab2, iCont, r1, 0); VdbeCoverage(v);
      sqlite3ReleaseTempReg(pParse, r1);
      selectInnerLoop(pParse, p, p->pEList, tab1,
                      0, 0, &dest, iCont, iBreak);
      sqlite3VdbeResolveLabel(v, iCont);
      sqlite3VdbeAddOp2(v, OP_Next, tab1, iStart); VdbeCoverage(v);
      sqlite3VdbeResolveLabel(v, iBreak);
      sqlite3VdbeAddOp2(v, OP_Close, tab2, 0);
      sqlite3VdbeAddOp2(v, OP_Close, tab1, 0);
      break;
    }

      Expr *pE = pFunc->pExpr;
      assert( !ExprHasProperty(pE, EP_xIsSelect) );
      if( pE->x.pList==0 || pE->x.pList->nExpr!=1 ){
        sqlite3ErrorMsg(pParse, "DISTINCT aggregates must have exactly one "
           "argument");
        pFunc->iDistinct = -1;
      }else{
        KeyInfo *pKeyInfo = keyInfoFromExprList(pParse, pE->x.pList, 0, 0);
        sqlite3VdbeAddOp4(v, OP_OpenEphemeral, pFunc->iDistinct, 0, 0,
                          (char*)pKeyInfo, P4_KEYINFO);
      }
    }
  }
}

  int i, j;              /* Loop counters */
  WhereInfo *pWInfo;     /* Return from sqlite3WhereBegin() */
  Vdbe *v;               /* The virtual machine under construction */
  int isAgg;             /* True for select lists like "count(*)" */
  ExprList *pEList;      /* List of columns to extract. */
  SrcList *pTabList;     /* List of tables to select from */
  Expr *pWhere;          /* The WHERE clause.  May be NULL */

  ExprList *pGroupBy;    /* The GROUP BY clause.  May be NULL */
  Expr *pHaving;         /* The HAVING clause.  May be NULL */
  int rc = 1;            /* Value to return from this function */

  DistinctCtx sDistinct; /* Info on how to code the DISTINCT keyword */
  SortCtx sSort;         /* Info on how to code the ORDER BY clause */
  AggInfo sAggInfo;      /* Information used by aggregate queries */
  int iEnd;              /* Address of the end of the query */
  sqlite3 *db;           /* The database connection */

#ifndef SQLITE_OMIT_EXPLAIN
  int iRestoreSelectId = pParse->iSelectId;
  pParse->iSelectId = pParse->iNextSelectId++;

    /* If ORDER BY makes no difference in the output then neither does
    ** DISTINCT so it can be removed too. */
    sqlite3ExprListDelete(db, p->pOrderBy);
    p->pOrderBy = 0;
    p->selFlags &= ~SF_Distinct;
  }
  sqlite3SelectPrep(pParse, p, 0);
  memset(&sSort, 0, sizeof(sSort));
  sSort.pOrderBy = p->pOrderBy;
  pTabList = p->pSrc;
  pEList = p->pEList;
  if( pParse->nErr || db->mallocFailed ){
    goto select_end;
  }
  isAgg = (p->selFlags & SF_Aggregate)!=0;
  assert( pEList!=0 );

    }
    if( /*pParse->nErr ||*/ db->mallocFailed ){
      goto select_end;
    }
    pParse->nHeight -= sqlite3SelectExprHeight(p);
    pTabList = p->pSrc;
    if( !IgnorableOrderby(pDest) ){
      sSort.pOrderBy = p->pOrderBy;
    }
  }
  pEList = p->pEList;
#endif
  pWhere = p->pWhere;
  pGroupBy = p->pGroupBy;
  pHaving = p->pHaving;

  /* If there is both a GROUP BY and an ORDER BY clause and they are
  ** identical, then disable the ORDER BY clause since the GROUP BY
  ** will cause elements to come out in the correct order.  This is
  ** an optimization - the correct answer should result regardless.
  ** Use the SQLITE_GroupByOrder flag with SQLITE_TESTCTRL_OPTIMIZER
  ** to disable this optimization for testing purposes.
  */
  if( sqlite3ExprListCompare(p->pGroupBy, sSort.pOrderBy, -1)==0
         && OptimizationEnabled(db, SQLITE_GroupByOrder) ){
    sSort.pOrderBy = 0;
  }

  /* If the query is DISTINCT with an ORDER BY but is not an aggregate, and 
  ** if the select-list is the same as the ORDER BY list, then this query
  ** can be rewritten as a GROUP BY. In other words, this:
  **
  **     SELECT DISTINCT xyz FROM ... ORDER BY xyz
  **
  ** is transformed to:
  **
  **     SELECT xyz FROM ... GROUP BY xyz
  **
  ** The second form is preferred as a single index (or temp-table) may be 
  ** used for both the ORDER BY and DISTINCT processing. As originally 
  ** written the query must use a temp-table for at least one of the ORDER 
  ** BY and DISTINCT, and an index or separate temp-table for the other.
  */
  if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct 
   && sqlite3ExprListCompare(sSort.pOrderBy, p->pEList, -1)==0
  ){
    p->selFlags &= ~SF_Distinct;
    p->pGroupBy = sqlite3ExprListDup(db, p->pEList, 0);
    pGroupBy = p->pGroupBy;
    sSort.pOrderBy = 0;
    /* Notice that even thought SF_Distinct has been cleared from p->selFlags,
    ** the sDistinct.isTnct is still set.  Hence, isTnct represents the
    ** original setting of the SF_Distinct flag, not the current setting */
    assert( sDistinct.isTnct );
  }

  /* If there is an ORDER BY clause, then this sorting
  ** index might end up being unused if the data can be 
  ** extracted in pre-sorted order.  If that is the case, then the
  ** OP_OpenEphemeral instruction will be changed to an OP_Noop once
  ** we figure out that the sorting index is not needed.  The addrSortIndex
  ** variable is used to facilitate that change.
  */
  if( sSort.pOrderBy ){
    KeyInfo *pKeyInfo;
    pKeyInfo = keyInfoFromExprList(pParse, sSort.pOrderBy, 0, 0);
    sSort.iECursor = pParse->nTab++;
    sSort.addrSortIndex =
      sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
                           sSort.iECursor, sSort.pOrderBy->nExpr+2, 0,
                           (char*)pKeyInfo, P4_KEYINFO);
  }else{
    sSort.addrSortIndex = -1;
  }

  /* If the output is destined for a temporary table, open that table.
  */
  if( pDest->eDest==SRT_EphemTab ){
    sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pDest->iSDParm, pEList->nExpr);
  }

  /* Set the limiter.
  */
  iEnd = sqlite3VdbeMakeLabel(v);
  p->nSelectRow = LARGEST_INT64;
  computeLimitRegisters(pParse, p, iEnd);
  if( p->iLimit==0 && sSort.addrSortIndex>=0 ){
    sqlite3VdbeGetOp(v, sSort.addrSortIndex)->opcode = OP_SorterOpen;
    sSort.sortFlags |= SORTFLAG_UseSorter;
  }

  /* Open a virtual index to use for the distinct set.
  */
  if( p->selFlags & SF_Distinct ){
    sDistinct.tabTnct = pParse->nTab++;
    sDistinct.addrTnct = sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
                                sDistinct.tabTnct, 0, 0,
                                (char*)keyInfoFromExprList(pParse, p->pEList,0,0),
                                P4_KEYINFO);
    sqlite3VdbeChangeP5(v, BTREE_UNORDERED);
    sDistinct.eTnctType = WHERE_DISTINCT_UNORDERED;
  }else{
    sDistinct.eTnctType = WHERE_DISTINCT_NOOP;
  }

  if( !isAgg && pGroupBy==0 ){
    /* No aggregate functions and no GROUP BY clause */
    u16 wctrlFlags = (sDistinct.isTnct ? WHERE_WANT_DISTINCT : 0);


    /* Begin the database scan. */
    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, sSort.pOrderBy,
                               p->pEList, wctrlFlags, 0);
    if( pWInfo==0 ) goto select_end;
    if( sqlite3WhereOutputRowCount(pWInfo) < p->nSelectRow ){
      p->nSelectRow = sqlite3WhereOutputRowCount(pWInfo);
    }
    if( sDistinct.isTnct && sqlite3WhereIsDistinct(pWInfo) ){
      sDistinct.eTnctType = sqlite3WhereIsDistinct(pWInfo);
    }
    if( sSort.pOrderBy ){
      sSort.nOBSat = sqlite3WhereIsOrdered(pWInfo);
      if( sSort.nOBSat==sSort.pOrderBy->nExpr ){
        sSort.pOrderBy = 0;
      }
    }

    /* If sorting index that was created by a prior OP_OpenEphemeral 
    ** instruction ended up not being needed, then change the OP_OpenEphemeral
    ** into an OP_Noop.
    */
    if( sSort.addrSortIndex>=0 && sSort.pOrderBy==0 ){
      sqlite3VdbeChangeToNoop(v, sSort.addrSortIndex);

    }

    /* Use the standard inner loop. */
    selectInnerLoop(pParse, p, pEList, -1, &sSort, &sDistinct, pDest,
                    sqlite3WhereContinueLabel(pWInfo),
                    sqlite3WhereBreakLabel(pWInfo));

    /* End the database scan loop.
    */
    sqlite3WhereEnd(pWInfo);
  }else{

    sNC.pParse = pParse;
    sNC.pSrcList = pTabList;
    sNC.pAggInfo = &sAggInfo;
    sAggInfo.mnReg = pParse->nMem+1;
    sAggInfo.nSortingColumn = pGroupBy ? pGroupBy->nExpr+1 : 0;
    sAggInfo.pGroupBy = pGroupBy;
    sqlite3ExprAnalyzeAggList(&sNC, pEList);
    sqlite3ExprAnalyzeAggList(&sNC, sSort.pOrderBy);
    if( pHaving ){
      sqlite3ExprAnalyzeAggregates(&sNC, pHaving);
    }
    sAggInfo.nAccumulator = sAggInfo.nColumn;
    for(i=0; i<sAggInfo.nFunc; i++){
      assert( !ExprHasProperty(sAggInfo.aFunc[i].pExpr, EP_xIsSelect) );
      sNC.ncFlags |= NC_InAggFunc;

      /* If there is a GROUP BY clause we might need a sorting index to
      ** implement it.  Allocate that sorting index now.  If it turns out
      ** that we do not need it after all, the OP_SorterOpen instruction
      ** will be converted into a Noop.  
      */
      sAggInfo.sortingIdx = pParse->nTab++;
      pKeyInfo = keyInfoFromExprList(pParse, pGroupBy, 0, 0);
      addrSortingIdx = sqlite3VdbeAddOp4(v, OP_SorterOpen, 
          sAggInfo.sortingIdx, sAggInfo.nSortingColumn, 
          0, (char*)pKeyInfo, P4_KEYINFO);

      /* Initialize memory locations used by GROUP BY aggregate processing
      */
      iUseFlag = ++pParse->nMem;

      sqlite3VdbeResolveLabel(v, addrOutputRow);
      addrOutputRow = sqlite3VdbeCurrentAddr(v);
      sqlite3VdbeAddOp2(v, OP_IfPos, iUseFlag, addrOutputRow+2); VdbeCoverage(v);
      VdbeComment((v, "Groupby result generator entry point"));
      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
      finalizeAggFunctions(pParse, &sAggInfo);
      sqlite3ExprIfFalse(pParse, pHaving, addrOutputRow+1, SQLITE_JUMPIFNULL);
      selectInnerLoop(pParse, p, p->pEList, -1, &sSort,
                      &sDistinct, pDest,
                      addrOutputRow+1, addrSetAbort);
      sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
      VdbeComment((v, "end groupby result generator"));

      /* Generate a subroutine that will reset the group-by accumulator
      */

          VdbeComment((v, "%s() by index",
                (flag==WHERE_ORDERBY_MIN?"min":"max")));
        }
        sqlite3WhereEnd(pWInfo);
        finalizeAggFunctions(pParse, &sAggInfo);
      }

      sSort.pOrderBy = 0;
      sqlite3ExprIfFalse(pParse, pHaving, addrEnd, SQLITE_JUMPIFNULL);
      selectInnerLoop(pParse, p, p->pEList, -1, 0, 0, 
                      pDest, addrEnd, addrEnd);
      sqlite3ExprListDelete(db, pDel);
    }
    sqlite3VdbeResolveLabel(v, addrEnd);
    
  } /* endif aggregate query */

  if( sDistinct.eTnctType==WHERE_DISTINCT_UNORDERED ){
    explainTempTable(pParse, "DISTINCT");
  }

  /* If there is an ORDER BY clause, then we need to sort the results
  ** and send them to the callback one by one.
  */
  if( sSort.pOrderBy ){
    explainTempTable(pParse, "ORDER BY");
    generateSortTail(pParse, p, &sSort, pEList->nExpr, pDest);
  }

  /* Jump here to skip this query
  */
  sqlite3VdbeResolveLabel(v, iEnd);

  /* The SELECT was successfully coded.   Set the return code to 0

** column expression as it exists in a SELECT statement.  However, if
** the bSpanIsTab flag is set, then zSpan is overloaded to mean the name
** of the result column in the form: DATABASE.TABLE.COLUMN.  This later
** form is used for name resolution with nested FROM clauses.
*/
struct ExprList {
  int nExpr;             /* Number of expressions on the list */

  struct ExprList_item { /* For each expression in the list */
    Expr *pExpr;            /* The list of expressions */
    char *zName;            /* Token associated with this expression */
    char *zSpan;            /* Original text of the expression */
    u8 sortOrder;           /* 1 for DESC or 0 for ASC */
    unsigned done :1;       /* A flag to indicate when processing is finished */
    unsigned bSpanIsTab :1; /* zSpan holds DB.TABLE.COLUMN */

** sequences for the ORDER BY clause.
*/
struct Select {
  ExprList *pEList;      /* The fields of the result */
  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[2];   /* OP_OpenEphem opcodes related to this select */
  u64 nSelectRow;        /* Estimated number of result rows */
  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 */

*/
#define SF_Distinct        0x0001  /* Output should be DISTINCT */
#define SF_Resolved        0x0002  /* Identifiers have been resolved */
#define SF_Aggregate       0x0004  /* Contains aggregate functions */
#define SF_UsesEphemeral   0x0008  /* Uses the OpenEphemeral opcode */
#define SF_Expanded        0x0010  /* sqlite3SelectExpand() called on this */
#define SF_HasTypeInfo     0x0020  /* FROM subqueries have Table metadata */
                    /*     0x0040  NOT USED */
#define SF_Values          0x0080  /* Synthesized from VALUES clause */
                    /*     0x0100  NOT USED */
#define SF_NestedFrom      0x0200  /* Part of a parenthesized FROM clause */
#define SF_MaybeConvert    0x0400  /* Need convertCompoundSelectToSubquery() */
#define SF_Recursive       0x0800  /* The recursive part of a recursive CTE */
#define SF_Compound        0x1000  /* Part of a compound query */


/*

  UPDATE_MAX_BLOBSIZE(pOut);
  break;
}

/* Opcode: Move P1 P2 P3 * *
** Synopsis:  r[P2@P3]=r[P1@P3]
**
** Move the P3 values in register P1..P1+P3-1 over into
** registers P2..P2+P3-1.  Registers P1..P1+P3-1 are
** left holding a NULL.  It is an error for register ranges
** P1..P1+P3-1 and P2..P2+P3-1 to overlap.  It is an error
** for P3 to be less than 1.
*/
case OP_Move: {
  char *zMalloc;   /* Holding variable for allocated memory */
  int n;           /* Number of registers left to copy */
  int p1;          /* Register to copy from */
  int p2;          /* Register to copy to */

  n = pOp->p3;
  p1 = pOp->p1;
  p2 = pOp->p2;
  assert( n>0 && p1>0 && p2>0 );
  assert( p1+n<=p2 || p2+n<=p1 );

  pIn1 = &aMem[p1];
  pOut = &aMem[p2];
  do{
    assert( pOut<=&aMem[(p->nMem-p->nCursor)] );
    assert( pIn1<=&aMem[(p->nMem-p->nCursor)] );

#endif
    pIn1->flags = MEM_Undefined;
    pIn1->xDel = 0;
    pIn1->zMalloc = zMalloc;
    REGISTER_TRACE(p2++, pOut);
    pIn1++;
    pOut++;
  }while( --n );
  break;
}

/* Opcode: Copy P1 P2 P3 * *
** Synopsis: r[P2@P3+1]=r[P1@P3+1]
**
** Make a copy of registers P1..P1+P3 into registers P2..P2+P3.

  assert( pOp->p4type==P4_INTARRAY );
  assert( pOp->p4.ai );
  aPermute = pOp->p4.ai;
  break;
}

/* Opcode: Compare P1 P2 P3 P4 P5
** Synopsis: r[P1@P3] <-> r[P2@P3]
**
** Compare two vectors of registers in reg(P1)..reg(P1+P3-1) (call this
** vector "A") and in reg(P2)..reg(P2+P3-1) ("B").  Save the result of
** the comparison for use by the next OP_Jump instruct.
**
** If P5 has the OPFLAG_PERMUTE bit set, then the order of comparison is
** determined by the most recent OP_Permutation operator.  If the

      SQLITE_OPEN_DELETEONCLOSE |
      SQLITE_OPEN_TRANSIENT_DB;
  assert( pOp->p1>=0 );
  assert( pOp->p2>=0 );
  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, 1);
  if( pCx==0 ) goto no_mem;
  pCx->nullRow = 1;
  pCx->isEphemeral = 1;
  rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pCx->pBt, 
                        BTREE_OMIT_JOURNAL | BTREE_SINGLE | pOp->p5, vfsFlags);
  if( rc==SQLITE_OK ){
    rc = sqlite3BtreeBeginTrans(pCx->pBt, 1);
  }
  if( rc==SQLITE_OK ){
    /* If a transient index is required, create it by calling

    assert( pC->rowidIsValid==0 );
  }
  pC->seekResult = res;
  break;
}

/* Opcode: Sequence P1 P2 * * *
** Synopsis: r[P2]=cursor[P1].ctr++
**
** Find the next available sequence number for cursor P1.
** Write the sequence number into register P2.
** The sequence number on the cursor is incremented after this
** instruction.  
*/
case OP_Sequence: {           /* out2-prerelease */

      assert( memIsValid(&aMem[pOp->p3]) );
      memAboutToChange(p, &aMem[pOp->p3]);
      aMem[pOp->p3].u.i += nChange;
    }
  }
  break;
}

/* Opcode: ClearEphem P1 * * * *
**
** Delete all contents from the ephemeral table that is open on cursor P1.
**
** See also: Clear, Destroy
*/
case OP_ClearEphem: {
  VdbeCursor *pC;
 
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->isEphemeral );
  rc = sqlite3BtreeClearTableOfCursor(pC->pCursor);
  break;
}

/* Opcode: CreateTable P1 P2 * * *
** Synopsis: r[P2]=root iDb=P1
**
** Allocate a new table in the main database file if P1==0 or in the
** auxiliary database file if P1==1 or in an attached database if
** P1>1.  Write the root page number of the new table into

  int pseudoTableReg;   /* Register holding pseudotable content. */
  i16 nField;           /* Number of fields in the header */
  u16 nHdrParsed;       /* Number of header fields parsed so far */
  i8 iDb;               /* Index of cursor database in db->aDb[] (or -1) */
  u8 nullRow;           /* True if pointing to a row with no data */
  u8 rowidIsValid;      /* True if lastRowid is valid */
  u8 deferredMoveto;    /* A call to sqlite3BtreeMoveto() is needed */
  Bool isEphemeral:1;   /* True for an ephemeral table */
  Bool useRandomRowid:1;/* Generate new record numbers semi-randomly */
  Bool isTable:1;       /* True if a table requiring integer keys */
  Bool isOrdered:1;     /* True if the underlying table is BTREE_UNORDERED */
  sqlite3_vtab_cursor *pVtabCursor;  /* The cursor for a virtual table */
  i64 seqCount;         /* Sequence counter */
  i64 movetoTarget;     /* Argument to the deferred sqlite3BtreeMoveto() */
  i64 lastRowid;        /* Rowid being deleted by OP_Delete */

  }
  assert( p->nOp>0 );
  assert( addr<p->nOp );
  if( addr<0 ){
    addr = p->nOp - 1;
  }
  pOp = &p->aOp[addr];
  assert( pOp->p4type==P4_NOTUSED
       || pOp->p4type==P4_INT32
       || pOp->p4type==P4_KEYINFO );
  freeP4(db, pOp->p4type, pOp->p4.p);
  pOp->p4.p = 0;
  if( n==P4_INT32 ){
    /* Note: this cast is safe, because the origin data point was an int
    ** that was cast to a (const char *). */
    pOp->p4.i = SQLITE_PTR_TO_INT(zP4);
    pOp->p4type = P4_INT32;

    Bitmask notUsed;
    int rc = wherePathSatisfiesOrderBy(pWInfo, pWInfo->pResultSet, pFrom,
                 WHERE_DISTINCTBY, nLoop-1, pFrom->aLoop[nLoop-1], &notUsed);
    if( rc==pWInfo->pResultSet->nExpr ){
      pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
    }
  }
  if( pWInfo->pOrderBy ){
    if( pWInfo->wctrlFlags & WHERE_DISTINCTBY ){
      if( pFrom->isOrdered==pWInfo->pOrderBy->nExpr ){
      pWInfo->eDistinct = WHERE_DISTINCT_ORDERED;
      }
    }else{
      pWInfo->nOBSat = pFrom->isOrdered;
      pWInfo->revMask = pFrom->revLoop;
    }
  }
  pWInfo->nRowOut = pFrom->nRow;