}else{
        sqlite3VdbeChangeP3(v, -1, pWin->regResult);
      }
    }
  }
}























































/*
** ROWS BETWEEN <expr1> PRECEDING AND <expr2> FOLLOWING
** ----------------------------------------------------
**
** Pseudo-code for the implementation of this window frame type is as
** follows. sqlite3WhereBegin() has already been called to generate the
................................................................................
  int regGosub, 
  int addrGosub
){
  Window *pMWin = p->pWin;
  Vdbe *v = sqlite3GetVdbe(pParse);
  Window *pWin;
  int k;
  int iSubCsr = p->pSrc->a[0].iCursor;
  int nSub = p->pSrc->a[0].pTab->nCol;
  int regFlushPart;               /* Register for "Gosub flush_partition" */
  int lblFlushPart;               /* Label for "Gosub flush_partition" */
  int lblFlushDone;               /* Label for "Gosub flush_partition_done" */

  int reg = pParse->nMem+1;
  int regRecord = reg+nSub;
  int regRowid = regRecord+1;
  int addr;
  int csrStart = pParse->nTab++;
  int csrEnd = pParse->nTab++;
  int regStart;                    /* Value of <expr> PRECEDING */
  int regEnd;                      /* Value of <expr> FOLLOWING */
  int addrNext;
  int addrGoto;
................................................................................
  if( pMWin->eType==TK_RANGE 
   && pMWin->eStart==TK_CURRENT 
   && pMWin->eEnd==TK_UNBOUNDED
  ){
    bRange = 1;
  }

  pParse->nMem += nSub + 2;

  /* Allocate register and label for the "flush_partition" sub-routine. */
  regFlushPart = ++pParse->nMem;
  lblFlushPart = sqlite3VdbeMakeLabel(v);
  lblFlushDone = sqlite3VdbeMakeLabel(v);

  regStart = ++pParse->nMem;
  regEnd = ++pParse->nMem;

  /* Martial the row returned by the sub-select into an array of 
  ** registers. */
  for(k=0; k<nSub; k++){
    sqlite3VdbeAddOp3(v, OP_Column, iSubCsr, k, reg+k);
  }
  sqlite3VdbeAddOp3(v, OP_MakeRecord, reg, nSub, regRecord);

  /* Check if this is the start of a new partition. If so, call the
  ** flush_partition sub-routine.  */
  if( pMWin->pPartition ){
    ExprList *pPart = pMWin->pPartition;
    int nPart = (pPart ? pPart->nExpr : 0);
    int regNewPart = reg + pMWin->nBufferCol;
    KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pPart, 0, 0);

    addr = sqlite3VdbeAddOp3(v, OP_Compare, regNewPart, pMWin->regPart,nPart);
    sqlite3VdbeAppendP4(v, (void*)pKeyInfo, P4_KEYINFO);
    sqlite3VdbeAddOp3(v, OP_Jump, addr+2, addr+4, addr+2);
    sqlite3VdbeAddOp2(v, OP_Gosub, regFlushPart, lblFlushPart);
    sqlite3VdbeAddOp3(v, OP_Copy, regNewPart, pMWin->regPart, nPart);
  }

  /* Buffer the current row in the ephemeral table. */
  sqlite3VdbeAddOp2(v, OP_NewRowid, pMWin->iEphCsr, regRowid);
  sqlite3VdbeAddOp3(v, OP_Insert, pMWin->iEphCsr, regRecord, regRowid);

  /* End of the input loop */
  sqlite3WhereEnd(pWInfo);

  /* Invoke "flush_partition" to deal with the final (or only) partition */
  sqlite3VdbeAddOp2(v, OP_Gosub, regFlushPart, lblFlushPart);
  addrGoto = sqlite3VdbeAddOp0(v, OP_Goto);

  /* Start of "flush_partition" */
  sqlite3VdbeResolveLabel(v, lblFlushPart);
  sqlite3VdbeAddOp2(v, OP_Once, 0, sqlite3VdbeCurrentAddr(v)+3);
  sqlite3VdbeAddOp2(v, OP_OpenDup, csrStart, pMWin->iEphCsr);
  sqlite3VdbeAddOp2(v, OP_OpenDup, csrEnd, pMWin->iEphCsr);
................................................................................
  */
  if( pMWin->pEnd && pMWin->pStart && pMWin->eStart==TK_FOLLOWING ){
    assert( pMWin->eEnd==TK_FOLLOWING );
    sqlite3VdbeAddOp3(v, OP_Subtract, regStart, regEnd, regEnd);
  }

  /* Initialize the accumulator register for each window function to NULL */

  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
    sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regAccum);

  }



  sqlite3VdbeAddOp2(v, OP_Rewind, pMWin->iEphCsr, lblFlushDone);
  sqlite3VdbeAddOp2(v, OP_Rewind, csrStart, lblFlushDone);
  sqlite3VdbeChangeP5(v, 1);
  sqlite3VdbeAddOp2(v, OP_Rewind, csrEnd, lblFlushDone);
  sqlite3VdbeChangeP5(v, 1);

................................................................................
  ** do nothing.  */
  addrTop = sqlite3VdbeCurrentAddr(v);
  if( pMWin->eEnd==TK_PRECEDING ){
    addrIfPos1 = sqlite3VdbeAddOp3(v, OP_IfPos, regEnd, 0 , 1);
  }
  sqlite3VdbeAddOp2(v, OP_Next, csrEnd, sqlite3VdbeCurrentAddr(v)+2);
  addr = sqlite3VdbeAddOp0(v, OP_Goto);
  windowAggStep(pParse, pMWin, csrEnd, 0, reg);
  if( pMWin->eEnd==TK_UNBOUNDED ){
    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrTop);
    sqlite3VdbeJumpHere(v, addr);
    addrTop = sqlite3VdbeCurrentAddr(v);
  }else{
    sqlite3VdbeJumpHere(v, addr);
    if( pMWin->eEnd==TK_PRECEDING ){
................................................................................
      addrJumpHere = sqlite3VdbeAddOp3(v, OP_IfPos, regStart, 0 , 1);
    }
    if( bRange ){
      sqlite3VdbeAddOp3(v, OP_IfPos, regPeer, sqlite3VdbeCurrentAddr(v)+2, 1);
      addrJumpHere = sqlite3VdbeAddOp0(v, OP_Goto);
    }
    sqlite3VdbeAddOp2(v, OP_Next, csrStart, sqlite3VdbeCurrentAddr(v)+1);
    windowAggStep(pParse, pMWin, csrStart, 1, reg);
    if( bRange ){
      sqlite3VdbeAddOp2(v, OP_Goto, 0, addrJumpHere-1);
    }
    if( addrJumpHere ){
      sqlite3VdbeJumpHere(v, addrJumpHere);
    }
  }
................................................................................
  /* Jump to here to skip over flush_partition */
  sqlite3VdbeJumpHere(v, addrGoto);
}

/*
** RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
**












































































































































**   ...
**     if( new partition ){
**       AggFinal (xFinalize)
**       Gosub addrGosub
**       ResetSorter eph-table
**     }
**     else if( new peer ){
................................................................................
**       ResetSorter eph-table
**     }
**     AggStep
**     Insert (record into eph-table)
**   sqlite3WhereEnd()
**   AggFinal (xFinalize)
**   Gosub addrGosub














*/
static void windowCodeDefaultStep(
  Parse *pParse, 
  Select *p,
  WhereInfo *pWInfo,
  int regGosub, 
  int addrGosub
................................................................................
  WhereInfo *pWInfo,
  int regGosub, 
  int addrGosub,
  int *pbLoop
){
  Window *pMWin = p->pWin;


  if( (pMWin->eType==TK_ROWS 
   && (pMWin->eStart!=TK_UNBOUNDED||pMWin->eEnd!=TK_CURRENT||!pMWin->pOrderBy))
   || (pMWin->eStart==TK_CURRENT&&pMWin->eEnd==TK_UNBOUNDED&&pMWin->pOrderBy)
  ){
    *pbLoop = 0;
    windowCodeRowExprStep(pParse, p, pWInfo, regGosub, addrGosub);
    return;
  }












  *pbLoop = 1;
  windowCodeDefaultStep(pParse, p, pWInfo, regGosub, addrGosub);
}

      }else{
        sqlite3VdbeChangeP3(v, -1, pWin->regResult);
      }
    }
  }
}

static void windowPartitionCache(
  Parse *pParse,
  Select *p,
  WhereInfo *pWInfo,
  int regFlushPart,
  int lblFlushPart
){
  Window *pMWin = p->pWin;
  Vdbe *v = sqlite3GetVdbe(pParse);
  Window *pWin;
  int iSubCsr = p->pSrc->a[0].iCursor;
  int nSub = p->pSrc->a[0].pTab->nCol;
  int k;

  int reg = pParse->nMem+1;
  int regRecord = reg+nSub;
  int regRowid = regRecord+1;

  pParse->nMem += nSub + 2;

  /* Martial the row returned by the sub-select into an array of 
  ** registers. */
  for(k=0; k<nSub; k++){
    sqlite3VdbeAddOp3(v, OP_Column, iSubCsr, k, reg+k);
  }
  sqlite3VdbeAddOp3(v, OP_MakeRecord, reg, nSub, regRecord);

  /* Check if this is the start of a new partition. If so, call the
  ** flush_partition sub-routine.  */
  if( pMWin->pPartition ){
    int addr;
    ExprList *pPart = pMWin->pPartition;
    int nPart = (pPart ? pPart->nExpr : 0);
    int regNewPart = reg + pMWin->nBufferCol;
    KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pPart, 0, 0);

    addr = sqlite3VdbeAddOp3(v, OP_Compare, regNewPart, pMWin->regPart,nPart);
    sqlite3VdbeAppendP4(v, (void*)pKeyInfo, P4_KEYINFO);
    sqlite3VdbeAddOp3(v, OP_Jump, addr+2, addr+4, addr+2);
    sqlite3VdbeAddOp3(v, OP_Copy, regNewPart, pMWin->regPart, nPart-1);
    sqlite3VdbeAddOp2(v, OP_Gosub, regFlushPart, lblFlushPart);
  }

  /* Buffer the current row in the ephemeral table. */
  sqlite3VdbeAddOp2(v, OP_NewRowid, pMWin->iEphCsr, regRowid);
  sqlite3VdbeAddOp3(v, OP_Insert, pMWin->iEphCsr, regRecord, regRowid);

  /* End of the input loop */
  sqlite3WhereEnd(pWInfo);

  /* Invoke "flush_partition" to deal with the final (or only) partition */
  sqlite3VdbeAddOp2(v, OP_Gosub, regFlushPart, lblFlushPart);
}

/*
** ROWS BETWEEN <expr1> PRECEDING AND <expr2> FOLLOWING
** ----------------------------------------------------
**
** Pseudo-code for the implementation of this window frame type is as
** follows. sqlite3WhereBegin() has already been called to generate the
................................................................................
  int regGosub, 
  int addrGosub
){
  Window *pMWin = p->pWin;
  Vdbe *v = sqlite3GetVdbe(pParse);
  Window *pWin;
  int k;

  int nSub = p->pSrc->a[0].pTab->nCol;
  int regFlushPart;               /* Register for "Gosub flush_partition" */
  int lblFlushPart;               /* Label for "Gosub flush_partition" */
  int lblFlushDone;               /* Label for "Gosub flush_partition_done" */

  int regArg;
  int nArg;

  int addr;
  int csrStart = pParse->nTab++;
  int csrEnd = pParse->nTab++;
  int regStart;                    /* Value of <expr> PRECEDING */
  int regEnd;                      /* Value of <expr> FOLLOWING */
  int addrNext;
  int addrGoto;
................................................................................
  if( pMWin->eType==TK_RANGE 
   && pMWin->eStart==TK_CURRENT 
   && pMWin->eEnd==TK_UNBOUNDED
  ){
    bRange = 1;
  }



  /* Allocate register and label for the "flush_partition" sub-routine. */
  regFlushPart = ++pParse->nMem;
  lblFlushPart = sqlite3VdbeMakeLabel(v);
  lblFlushDone = sqlite3VdbeMakeLabel(v);

  regStart = ++pParse->nMem;
  regEnd = ++pParse->nMem;



















  windowPartitionCache(pParse, p, pWInfo, regFlushPart, lblFlushPart);












  addrGoto = sqlite3VdbeAddOp0(v, OP_Goto);

  /* Start of "flush_partition" */
  sqlite3VdbeResolveLabel(v, lblFlushPart);
  sqlite3VdbeAddOp2(v, OP_Once, 0, sqlite3VdbeCurrentAddr(v)+3);
  sqlite3VdbeAddOp2(v, OP_OpenDup, csrStart, pMWin->iEphCsr);
  sqlite3VdbeAddOp2(v, OP_OpenDup, csrEnd, pMWin->iEphCsr);
................................................................................
  */
  if( pMWin->pEnd && pMWin->pStart && pMWin->eStart==TK_FOLLOWING ){
    assert( pMWin->eEnd==TK_FOLLOWING );
    sqlite3VdbeAddOp3(v, OP_Subtract, regStart, regEnd, regEnd);
  }

  /* Initialize the accumulator register for each window function to NULL */
  nArg = 0;
  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
    sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regAccum);
    nArg = MAX(nArg, pWin->nArg);
  }
  regArg = pParse->nMem+1;
  pParse->nMem += nArg;

  sqlite3VdbeAddOp2(v, OP_Rewind, pMWin->iEphCsr, lblFlushDone);
  sqlite3VdbeAddOp2(v, OP_Rewind, csrStart, lblFlushDone);
  sqlite3VdbeChangeP5(v, 1);
  sqlite3VdbeAddOp2(v, OP_Rewind, csrEnd, lblFlushDone);
  sqlite3VdbeChangeP5(v, 1);

................................................................................
  ** do nothing.  */
  addrTop = sqlite3VdbeCurrentAddr(v);
  if( pMWin->eEnd==TK_PRECEDING ){
    addrIfPos1 = sqlite3VdbeAddOp3(v, OP_IfPos, regEnd, 0 , 1);
  }
  sqlite3VdbeAddOp2(v, OP_Next, csrEnd, sqlite3VdbeCurrentAddr(v)+2);
  addr = sqlite3VdbeAddOp0(v, OP_Goto);
  windowAggStep(pParse, pMWin, csrEnd, 0, regArg);
  if( pMWin->eEnd==TK_UNBOUNDED ){
    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrTop);
    sqlite3VdbeJumpHere(v, addr);
    addrTop = sqlite3VdbeCurrentAddr(v);
  }else{
    sqlite3VdbeJumpHere(v, addr);
    if( pMWin->eEnd==TK_PRECEDING ){
................................................................................
      addrJumpHere = sqlite3VdbeAddOp3(v, OP_IfPos, regStart, 0 , 1);
    }
    if( bRange ){
      sqlite3VdbeAddOp3(v, OP_IfPos, regPeer, sqlite3VdbeCurrentAddr(v)+2, 1);
      addrJumpHere = sqlite3VdbeAddOp0(v, OP_Goto);
    }
    sqlite3VdbeAddOp2(v, OP_Next, csrStart, sqlite3VdbeCurrentAddr(v)+1);
    windowAggStep(pParse, pMWin, csrStart, 1, regArg);
    if( bRange ){
      sqlite3VdbeAddOp2(v, OP_Goto, 0, addrJumpHere-1);
    }
    if( addrJumpHere ){
      sqlite3VdbeJumpHere(v, addrJumpHere);
    }
  }
................................................................................
  /* Jump to here to skip over flush_partition */
  sqlite3VdbeJumpHere(v, addrGoto);
}

/*
** RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
**
**   flush_partition:
**     Once {
**       OpenDup (iEphCsr -> csrLead)
**     }
**     Integer ctr 0
**     foreach row (csrLead){
**       if( new peer ){
**         AggFinal (xValue)
**         for(i=0; i<ctr; i++){
**           Gosub addrGosub
**           Next iEphCsr
**         }
**         Integer ctr 0
**       }
**       AggStep (csrLead)
**       Incr ctr
**     }
**
**     AggFinal (xFinalize)
**     for(i=0; i<ctr; i++){
**       Gosub addrGosub
**       Next iEphCsr
**     }
**
**     ResetSorter (csr)
**     Return
**
** ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
** RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
** RANGE BETWEEN CURRENT ROW AND CURRENT ROW 
**
**   TODO.
*/
static void windowCodeCacheStep(
  Parse *pParse, 
  Select *p,
  WhereInfo *pWInfo,
  int regGosub, 
  int addrGosub
){
  Window *pMWin = p->pWin;
  Vdbe *v = sqlite3GetVdbe(pParse);
  Window *pWin;
  int k;
  int addr;
  ExprList *pPart = pMWin->pPartition;
  ExprList *pOrderBy = pMWin->pOrderBy;
  int nPeer = pOrderBy->nExpr;
  int regNewPeer;

  int addrGoto;                   /* Address of Goto used to jump flush_par.. */
  int addrRewind;                 /* Address of Rewind that starts loop */
  int regFlushPart;
  int lblFlushPart;
  int csrLead;
  int regCtr;
  int regArg;                     /* Register array to martial function args */
  int nArg;

  assert( (pMWin->eStart==TK_UNBOUNDED && pMWin->eEnd==TK_CURRENT) 
  );

  regNewPeer = pParse->nMem+1;
  pParse->nMem += nPeer;

  /* Allocate register and label for the "flush_partition" sub-routine. */
  regFlushPart = ++pParse->nMem;
  lblFlushPart = sqlite3VdbeMakeLabel(v);

  csrLead = pParse->nTab++;
  regCtr = ++pParse->nMem;

  windowPartitionCache(pParse, p, pWInfo, regFlushPart, lblFlushPart);
  addrGoto = sqlite3VdbeAddOp0(v, OP_Goto);

  /* Start of "flush_partition" */
  sqlite3VdbeResolveLabel(v, lblFlushPart);
  sqlite3VdbeAddOp2(v, OP_Once, 0, sqlite3VdbeCurrentAddr(v)+2);
  sqlite3VdbeAddOp2(v, OP_OpenDup, csrLead, pMWin->iEphCsr);

  /* Initialize the accumulator register for each window function to NULL */
  nArg = 0;
  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
    sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regAccum);
    nArg = MAX(nArg, pWin->nArg);
  }
  regArg = pParse->nMem+1;
  pParse->nMem += nArg;

  sqlite3VdbeAddOp2(v, OP_Integer, 0, regCtr);
  addrRewind = sqlite3VdbeAddOp1(v, OP_Rewind, csrLead);
  sqlite3VdbeAddOp1(v, OP_Rewind, pMWin->iEphCsr);

  if( pOrderBy ){
    int addrJump;                 /* Address of OP_Jump below */
    int iOff = pMWin->nBufferCol + (pPart ? pPart->nExpr : 0);
    int regPeer = pMWin->regPart + (pPart ? pPart->nExpr : 0);
    KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pOrderBy, 0, 0);

    for(k=0; k<nPeer; k++){
      sqlite3VdbeAddOp3(v, OP_Column, csrLead, iOff+k, regNewPeer+k);
    }

    addr = sqlite3VdbeAddOp3(v, OP_Compare, regNewPeer, regPeer, nPeer);
    sqlite3VdbeAppendP4(v, (void*)pKeyInfo, P4_KEYINFO);
    addrJump = sqlite3VdbeAddOp3(v, OP_Jump, addr+2, 0, addr+2);
    sqlite3VdbeAddOp3(v, OP_Copy, regNewPeer, regPeer, nPeer-1);
    windowAggFinal(pParse, pMWin, 0);
    sqlite3VdbeAddOp3(v, OP_IfPos, regCtr, sqlite3VdbeCurrentAddr(v)+2 , 1);
    sqlite3VdbeAddOp2(v, OP_Goto, 0, sqlite3VdbeCurrentAddr(v)+3);
    sqlite3VdbeAddOp2(v, OP_Gosub, regGosub, addrGosub);
    sqlite3VdbeAddOp2(v, OP_Next, pMWin->iEphCsr, sqlite3VdbeCurrentAddr(v)-3);
    sqlite3VdbeJumpHere(v, addrJump);
  }

  windowAggStep(pParse, pMWin, csrLead, 0, regArg);
  sqlite3VdbeAddOp2(v, OP_AddImm, regCtr, 1);

  sqlite3VdbeAddOp2(v, OP_Next, csrLead, addrRewind+2);

  windowAggFinal(pParse, pMWin, 1);

  sqlite3VdbeAddOp3(v, OP_IfPos, regCtr, sqlite3VdbeCurrentAddr(v)+2 , 1);
  sqlite3VdbeAddOp2(v, OP_Goto, 0, sqlite3VdbeCurrentAddr(v)+3);
  sqlite3VdbeAddOp2(v, OP_Gosub, regGosub, addrGosub);
  sqlite3VdbeAddOp2(v, OP_Next, pMWin->iEphCsr, sqlite3VdbeCurrentAddr(v)-3);

  sqlite3VdbeJumpHere(v, addrRewind);
  sqlite3VdbeJumpHere(v, addrRewind+1);
  sqlite3VdbeAddOp1(v, OP_ResetSorter, pMWin->iEphCsr);
  sqlite3VdbeAddOp1(v, OP_Return, regFlushPart);

  /* Jump to here to skip over flush_partition */
  sqlite3VdbeJumpHere(v, addrGoto);
}


/*
** RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
**
**   ...
**     if( new partition ){
**       AggFinal (xFinalize)
**       Gosub addrGosub
**       ResetSorter eph-table
**     }
**     else if( new peer ){
................................................................................
**       ResetSorter eph-table
**     }
**     AggStep
**     Insert (record into eph-table)
**   sqlite3WhereEnd()
**   AggFinal (xFinalize)
**   Gosub addrGosub
**
** RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
**
**   As above, except take no action for a "new peer". Invoke
**   the sub-routine once only for each partition.
**
** RANGE BETWEEN CURRENT ROW AND CURRENT ROW
**
**   As above, except that the "new peer" condition is handled in the
**   same way as "new partition" (so there is no "else if" block).
**
** ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
** 
**   As above, except assume every row is a "new peer".
*/
static void windowCodeDefaultStep(
  Parse *pParse, 
  Select *p,
  WhereInfo *pWInfo,
  int regGosub, 
  int addrGosub
................................................................................
  WhereInfo *pWInfo,
  int regGosub, 
  int addrGosub,
  int *pbLoop
){
  Window *pMWin = p->pWin;

  *pbLoop = 0;
  if( (pMWin->eType==TK_ROWS 
   && (pMWin->eStart!=TK_UNBOUNDED||pMWin->eEnd!=TK_CURRENT||!pMWin->pOrderBy))
   || (pMWin->eStart==TK_CURRENT&&pMWin->eEnd==TK_UNBOUNDED&&pMWin->pOrderBy)
  ){

    windowCodeRowExprStep(pParse, p, pWInfo, regGosub, addrGosub);
    return;
  }

#if 0
  if( pMWin->eType==TK_RANGE
   && pMWin->eStart==TK_UNBOUNDED
   && pMWin->eEnd==TK_CURRENT
   && pMWin->pOrderBy
  ){
    windowCodeCacheStep(pParse, p, pWInfo, regGosub, addrGosub);
    return;
  }
#endif

  *pbLoop = 1;
  windowCodeDefaultStep(pParse, p, pWInfo, regGosub, addrGosub);
}