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Overview
Comment:Fix other "ROWS BETWEEN" cases on this branch.
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SHA3-256: a5f68f66472610b5beb4fe28669fbbfe83a32742be73cecad9b2ae28f8a17b30
User & Date: dan 2019-03-07 20:47:46
Wiki:window-functions
Context
2019-03-08
20:02
Finish consolidation of window frame code. Add untested support for GROUPS frames. check-in: 954bf369 user: dan tags: window-functions
2019-03-07
20:47
Fix other "ROWS BETWEEN" cases on this branch. check-in: a5f68f66 user: dan tags: window-functions
19:26
Modify new window functions function so that cursors are stepped immediately after each operation, instead of immediately before. check-in: 093d2b25 user: dan tags: window-functions
Changes
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Changes to src/window.c.

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    }
  }
  regArg = pParse->nMem+1;
  pParse->nMem += nArg;
  return regArg;
}


/*
** This function does the work of sqlite3WindowCodeStep() for all "ROWS"
** window frame types except for "BETWEEN UNBOUNDED PRECEDING AND CURRENT
** ROW". Pseudo-code for each follows.
**
** ROWS BETWEEN <expr1> PRECEDING AND <expr2> FOLLOWING
**
**     ...
**       if( new partition ){
**         Gosub flush_partition
**       }
**       Insert (record in eph-table)
**     sqlite3WhereEnd()
**     Gosub flush_partition
**  
**   flush_partition:
**     Once {
**       OpenDup (iEphCsr -> csrStart)
**       OpenDup (iEphCsr -> csrEnd)
**     }
**     regStart = <expr1>                // PRECEDING expression
**     regEnd = <expr2>                  // FOLLOWING expression
**     if( regStart<0 || regEnd<0 ){ error! }
**     Rewind (csr,csrStart,csrEnd)      // if EOF goto flush_partition_done
**       Next(csrEnd)                    // if EOF skip Aggstep
**       Aggstep (csrEnd)
**       if( (regEnd--)<=0 ){
**         AggFinal (xValue)
**         Gosub addrGosub
**         Next(csr)                // if EOF goto flush_partition_done
**         if( (regStart--)<=0 ){
**           AggInverse (csrStart)
**           Next(csrStart)
**         }
**       }
**   flush_partition_done:
**     ResetSorter (csr)
**     Return
**
** ROWS BETWEEN <expr> PRECEDING    AND CURRENT ROW
** ROWS BETWEEN CURRENT ROW         AND <expr> FOLLOWING
** ROWS BETWEEN UNBOUNDED PRECEDING AND <expr> FOLLOWING
**
**   These are similar to the above. For "CURRENT ROW", intialize the
**   register to 0. For "UNBOUNDED PRECEDING" to infinity.
**
** ROWS BETWEEN <expr> PRECEDING    AND UNBOUNDED FOLLOWING
** ROWS BETWEEN CURRENT ROW         AND UNBOUNDED FOLLOWING
**
**     Rewind (csr,csrStart,csrEnd)    // if EOF goto flush_partition_done
**     while( 1 ){
**       Next(csrEnd)                  // Exit while(1) at EOF
**       Aggstep (csrEnd)
**     }
**     while( 1 ){
**       AggFinal (xValue)
**       Gosub addrGosub
**       Next(csr)                     // if EOF goto flush_partition_done
**       if( (regStart--)<=0 ){
**         AggInverse (csrStart)
**         Next(csrStart)
**       }
**     }
**
**   For the "CURRENT ROW AND UNBOUNDED FOLLOWING" case, the final if() 
**   condition is always true (as if regStart were initialized to 0).
**
** RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING
** 
**   This is the only RANGE case handled by this routine. It modifies the
**   second while( 1 ) loop in "ROWS BETWEEN CURRENT ... UNBOUNDED..." to
**   be:
**
**     while( 1 ){
**       AggFinal (xValue)
**       while( 1 ){
**         regPeer++
**         Gosub addrGosub
**         Next(csr)                     // if EOF goto flush_partition_done
**         if( new peer ) break;
**       }
**       while( (regPeer--)>0 ){
**         AggInverse (csrStart)
**         Next(csrStart)
**       }
**     }
**
** ROWS BETWEEN <expr> FOLLOWING    AND <expr> FOLLOWING
**
**   regEnd = regEnd - regStart
**   Rewind (csr,csrStart,csrEnd)   // if EOF goto flush_partition_done
**     Aggstep (csrEnd)
**     Next(csrEnd)                 // if EOF fall-through
**     if( (regEnd--)<=0 ){
**       if( (regStart--)<=0 ){
**         AggFinal (xValue)
**         Gosub addrGosub
**         Next(csr)              // if EOF goto flush_partition_done
**       }
**       AggInverse (csrStart)
**       Next (csrStart)
**     }
**
** ROWS BETWEEN <expr> PRECEDING    AND <expr> PRECEDING
**
**   Replace the bit after "Rewind" in the above with:
**
**     if( (regEnd--)<=0 ){
**       AggStep (csrEnd)
**       Next (csrEnd)
**     }
**     AggFinal (xValue)
**     Gosub addrGosub
**     Next(csr)                  // if EOF goto flush_partition_done
**     if( (regStart--)<=0 ){
**       AggInverse (csr2)
**       Next (csr2)
**     }
**
*/
static void windowCodeRowExprStep(
  Parse *pParse, 
  Select *p,
  WhereInfo *pWInfo,
  int regGosub, 
  int addrGosub
){
  Window *pMWin = p->pWin;
  Vdbe *v = sqlite3GetVdbe(pParse);
  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 addr;
  int csrStart = pParse->nTab++;
  int csrEnd = pParse->nTab++;
  int regStart;                    /* Value of <expr> PRECEDING */
  int regEnd;                      /* Value of <expr> FOLLOWING */
  int addrGoto;
  int addrTop;
  int addrIfPos1 = 0;
  int addrIfPos2 = 0;
  int regSize = 0;

  assert( pMWin->eStart==TK_PRECEDING 
       || pMWin->eStart==TK_CURRENT 
       || pMWin->eStart==TK_FOLLOWING 
       || pMWin->eStart==TK_UNBOUNDED 
  );
  assert( pMWin->eEnd==TK_FOLLOWING 
       || pMWin->eEnd==TK_CURRENT 
       || pMWin->eEnd==TK_UNBOUNDED 
       || pMWin->eEnd==TK_PRECEDING 
  );

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

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

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

  addrGoto = sqlite3VdbeAddOp0(v, OP_Goto);

  /* Start of "flush_partition" */
  sqlite3VdbeResolveLabel(v, lblFlushPart);
  sqlite3VdbeAddOp2(v, OP_Once, 0, sqlite3VdbeCurrentAddr(v)+3);
  VdbeCoverage(v);
  VdbeComment((v, "Flush_partition subroutine"));
  sqlite3VdbeAddOp2(v, OP_OpenDup, csrStart, pMWin->iEphCsr);
  sqlite3VdbeAddOp2(v, OP_OpenDup, csrEnd, pMWin->iEphCsr);

  /* If either regStart or regEnd are not non-negative integers, throw 
  ** an exception.  */
  if( pMWin->pStart ){
    sqlite3ExprCode(pParse, pMWin->pStart, regStart);
    windowCheckIntValue(pParse, regStart, 0);
  }
  if( pMWin->pEnd ){
    sqlite3ExprCode(pParse, pMWin->pEnd, regEnd);
    windowCheckIntValue(pParse, regEnd, 1);
  }

  /* If this is "ROWS <expr1> FOLLOWING AND ROWS <expr2> FOLLOWING", do:
  **
  **   if( regEnd<regStart ){
  **     // The frame always consists of 0 rows
  **     regStart = regSize;
  **   }
  **   regEnd = regEnd - regStart;
  */
  if( pMWin->pEnd && pMWin->eStart==TK_FOLLOWING ){
    assert( pMWin->pStart!=0 );
    assert( pMWin->eEnd==TK_FOLLOWING );
    sqlite3VdbeAddOp3(v, OP_Ge, regStart, sqlite3VdbeCurrentAddr(v)+2, regEnd);
    VdbeCoverageNeverNull(v);
    sqlite3VdbeAddOp2(v, OP_Copy, regSize, regStart);
    sqlite3VdbeAddOp3(v, OP_Subtract, regStart, regEnd, regEnd);
  }

  if( pMWin->pStart && pMWin->eEnd==TK_PRECEDING ){
    assert( pMWin->pEnd!=0 );
    assert( pMWin->eStart==TK_PRECEDING );
    sqlite3VdbeAddOp3(v, OP_Le, regStart, sqlite3VdbeCurrentAddr(v)+3, regEnd);
    VdbeCoverageNeverNull(v);
    sqlite3VdbeAddOp2(v, OP_Copy, regSize, regStart);
    sqlite3VdbeAddOp2(v, OP_Copy, regSize, regEnd);
  }

  /* Initialize the accumulator register for each window function to NULL */
  regArg = windowInitAccum(pParse, pMWin);

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

  /* Invoke AggStep function for each window function using the row that
  ** csrEnd currently points to. Or, if csrEnd is already at EOF,
  ** do nothing.  */
  addrTop = sqlite3VdbeCurrentAddr(v);
  if( pMWin->eEnd==TK_PRECEDING ){
    addrIfPos1 = sqlite3VdbeAddOp3(v, OP_IfPos, regEnd, 0 , 1);
    VdbeCoverage(v);
  }
  sqlite3VdbeAddOp2(v, OP_Next, csrEnd, sqlite3VdbeCurrentAddr(v)+2);
  VdbeCoverage(v);
  addr = sqlite3VdbeAddOp0(v, OP_Goto);
  windowAggStep(pParse, pMWin, csrEnd, 0, regArg, regSize);
  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 ){
      sqlite3VdbeJumpHere(v, addrIfPos1);
    }
  }

  if( pMWin->eEnd==TK_FOLLOWING ){
    addrIfPos1 = sqlite3VdbeAddOp3(v, OP_IfPos, regEnd, 0 , 1);
    VdbeCoverage(v);
  }
  if( pMWin->eStart==TK_FOLLOWING ){
    addrIfPos2 = sqlite3VdbeAddOp3(v, OP_IfPos, regStart, 0 , 1);
    VdbeCoverage(v);
  }
  windowAggFinal(pParse, pMWin, 0);
  windowReturnOneRow(pParse, pMWin, regGosub, addrGosub);
  sqlite3VdbeAddOp2(v, OP_Next, pMWin->iEphCsr, sqlite3VdbeCurrentAddr(v)+2);
  VdbeCoverage(v);
  sqlite3VdbeAddOp2(v, OP_Goto, 0, lblFlushDone);
  if( pMWin->eStart==TK_FOLLOWING ){
    sqlite3VdbeJumpHere(v, addrIfPos2);
  }

  if( pMWin->eStart==TK_CURRENT 
   || pMWin->eStart==TK_PRECEDING 
   || pMWin->eStart==TK_FOLLOWING 
  ){
    int lblSkipInverse = sqlite3VdbeMakeLabel(pParse);;
    if( pMWin->eStart==TK_PRECEDING ){
      sqlite3VdbeAddOp3(v, OP_IfPos, regStart, lblSkipInverse, 1);
      VdbeCoverage(v);
    }
    if( pMWin->eStart==TK_FOLLOWING ){
      sqlite3VdbeAddOp2(v, OP_Next, csrStart, sqlite3VdbeCurrentAddr(v)+2);
      VdbeCoverage(v);
      sqlite3VdbeAddOp2(v, OP_Goto, 0, lblSkipInverse);
    }else{
      sqlite3VdbeAddOp2(v, OP_Next, csrStart, sqlite3VdbeCurrentAddr(v)+1);
      VdbeCoverageAlwaysTaken(v);
    }
    windowAggStep(pParse, pMWin, csrStart, 1, regArg, regSize);
    sqlite3VdbeResolveLabel(v, lblSkipInverse);
  }
  if( pMWin->eEnd==TK_FOLLOWING ){
    sqlite3VdbeJumpHere(v, addrIfPos1);
  }
  sqlite3VdbeAddOp2(v, OP_Goto, 0, addrTop);

  /* flush_partition_done: */
  sqlite3VdbeResolveLabel(v, lblFlushDone);
  sqlite3VdbeAddOp1(v, OP_ResetSorter, pMWin->iEphCsr);
  sqlite3VdbeAddOp1(v, OP_Return, regFlushPart);
  VdbeComment((v, "end flush_partition subroutine"));

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

/* 
** Return true if the entire partition should be cached in the ephemeral
** table before processing any rows.
*/
static int windowCachePartition(Window *pMWin){
  Window *pWin;
  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
................................................................................
static int windowCodeOp(
 WindowCodeArg *p,
 int op,
 int csr,
 int regCountdown,
 int jumpOnEof
){

  int ret = 0;
  Vdbe *v = p->pVdbe;
  int addrIf = 0; 








  if( regCountdown>0 ){
    addrIf = sqlite3VdbeAddOp3(v, OP_IfPos, regCountdown, 0, 1);
  }

  switch( op ){
    case WINDOW_RETURN_ROW:
      windowAggFinal(p->pParse, p->pMWin, 0);
      windowReturnOneRow(p->pParse, p->pMWin, p->regGosub, p->addrGosub);
      break;

    case WINDOW_AGGINVERSE:
      windowAggStep(p->pParse, p->pMWin, csr, 1, p->regArg, p->pMWin->regSize);
      break;

    case WINDOW_AGGSTEP:
      windowAggStep(p->pParse, p->pMWin, csr, 0, p->regArg, p->pMWin->regSize);
      break;
  }

  if( jumpOnEof ){
    sqlite3VdbeAddOp2(v, OP_Next, csr, sqlite3VdbeCurrentAddr(v)+2);
    ret = sqlite3VdbeAddOp0(v, OP_Goto);
  }else{
................................................................................

  int regArg;
  int csrCurrent = pMWin->iEphCsr;
  int csrWrite = csrCurrent+1;
  int csrStart = csrCurrent+2;
  int csrEnd = csrCurrent+3;

  int regStart;                    /* Value of <expr> PRECEDING */
  int regEnd;                      /* Value of <expr> FOLLOWING */

  int iSubCsr = p->pSrc->a[0].iCursor;      /* Cursor of sub-select */
  int nSub = p->pSrc->a[0].pTab->nCol;      /* Number of cols returned by sub */
  int iCol;                                 /* To iterate through sub cols */

  int addrGoto;
  int addrIf;
................................................................................
  int addrCacheNext;

  int addrShortcut = 0;
  int addrEmpty = 0;

  int bCache = windowCachePartition(pMWin);




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

  memset(&s, 0, sizeof(WindowCodeArg));
  s.pParse = pParse;
................................................................................
  s.pVdbe = v;
  s.regGosub = regGosub;
  s.addrGosub = addrGosub;

  pParse->nMem += 1 + nSub + 1;

  regFlushPart = ++pParse->nMem;


  regStart = ++pParse->nMem;


  regEnd = ++pParse->nMem;


  assert( pMWin->eStart==TK_PRECEDING 
       || pMWin->eStart==TK_CURRENT 
       || pMWin->eStart==TK_FOLLOWING 
       || pMWin->eStart==TK_UNBOUNDED 
  );
  assert( pMWin->eEnd==TK_FOLLOWING 
................................................................................
  }else{
    addrIf = sqlite3VdbeAddOp1(v, OP_IfNot, pMWin->regFirst);
  }

  /* This block is run for the first row of each partition */
  s.regArg = regArg = windowInitAccum(pParse, pMWin);


  sqlite3ExprCode(pParse, pMWin->pStart, regStart);
  windowCheckIntValue(pParse, regStart, 0);


  sqlite3ExprCode(pParse, pMWin->pEnd, regEnd);
  windowCheckIntValue(pParse, regEnd, 1);


  if( pMWin->eStart==pMWin->eEnd 
   && pMWin->eStart!=TK_CURRENT && pMWin->eStart!=TK_UNBOUNDED 
  ){
    int op = ((pMWin->eStart==TK_FOLLOWING) ? OP_Ge : OP_Le);
    int addrGe = sqlite3VdbeAddOp3(v, op, regStart, 0, regEnd);
    windowAggFinal(pParse, pMWin, 0);
    if( bCache ){
      sqlite3VdbeAddOp2(v, OP_Rowid, csrWrite, regRowid);
      sqlite3VdbeAddOp3(v, OP_NotExists, csrCurrent, 0, regRowid);
      windowReturnOneRow(pParse, pMWin, regGosub, addrGosub);
................................................................................
      sqlite3VdbeAddOp2(v, OP_Rewind, csrCurrent, 1);
      windowReturnOneRow(pParse, pMWin, regGosub, addrGosub);
      sqlite3VdbeAddOp1(v, OP_ResetSorter, csrCurrent);
    }
    addrShortcut = sqlite3VdbeAddOp0(v, OP_Goto);
    sqlite3VdbeJumpHere(v, addrGe);
  }
  if( pMWin->eStart==TK_FOLLOWING ){

    sqlite3VdbeAddOp3(v, OP_Subtract, regStart, regEnd, regStart);
  }


  sqlite3VdbeAddOp2(v, OP_Rewind, csrStart, 1);

  sqlite3VdbeAddOp2(v, OP_Rewind, csrCurrent, 1);
  sqlite3VdbeAddOp2(v, OP_Rewind, csrEnd, 1);

  sqlite3VdbeAddOp2(v, OP_Integer, 0, pMWin->regFirst);
  addrGoto = sqlite3VdbeAddOp0(v, OP_Goto);

  /* Begin generating SECOND_ROW_CODE */
................................................................................
  if( bCache ){
    addrCacheNext = sqlite3VdbeCurrentAddr(v);
  }else{
    sqlite3VdbeJumpHere(v, addrIf);
  }
  if( pMWin->eStart==TK_FOLLOWING ){
    windowCodeOp(&s, WINDOW_AGGSTEP, csrEnd, 0, 0);

    windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, regEnd, 0);
    windowCodeOp(&s, WINDOW_AGGINVERSE, csrStart, regStart, 0);

  }else
  if( pMWin->eEnd==TK_PRECEDING ){
    windowCodeOp(&s, WINDOW_AGGSTEP, csrEnd, regEnd, 0);
    windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, 0, 0);
    windowCodeOp(&s, WINDOW_AGGINVERSE, csrStart, regStart, 0);
  }else{
    int addr;
    windowCodeOp(&s, WINDOW_AGGSTEP, csrEnd, 0, 0);

    addr = sqlite3VdbeAddOp3(v, OP_IfPos, regEnd, 0, 1);
    windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, 0, 0);
    windowCodeOp(&s, WINDOW_AGGINVERSE, csrStart, regStart, 0);
    sqlite3VdbeJumpHere(v, addr);

  }
  VdbeModuleComment((pParse->pVdbe, "End windowCodeStep.SECOND_ROW_CODE"));

  /* End of the main input loop */
  sqlite3VdbeJumpHere(v, addrGoto);
  if( bCache ){
    sqlite3VdbeAddOp2(v, OP_Next, csrWrite, addrCacheNext);
................................................................................
    windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, 0, 0);
  }else if( pMWin->eStart==TK_FOLLOWING ){
    int addrStart;
    int addrBreak1;
    int addrBreak2;
    int addrBreak3;
    windowCodeOp(&s, WINDOW_AGGSTEP, csrEnd, 0, 0);






    addrStart = sqlite3VdbeCurrentAddr(v);
    addrBreak1 = windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, regEnd, 1);
    addrBreak2 = windowCodeOp(&s, WINDOW_AGGINVERSE, csrStart, regStart, 1);

    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrStart);
    sqlite3VdbeJumpHere(v, addrBreak2);
    addrStart = sqlite3VdbeCurrentAddr(v);
    addrBreak3 = windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, 0, 1);
    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrStart);
    sqlite3VdbeJumpHere(v, addrBreak1);
    sqlite3VdbeJumpHere(v, addrBreak3);
................................................................................
  **   RANGE BETWEEN CURRENT ROW AND CURRENT ROW 
  **   ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
  **
  ** windowCodeDefaultStep() is the only one of the three functions that
  ** does not cache each partition in a temp table before beginning to
  ** return rows.
  */
  if( pMWin->eType==TK_ROWS 
   && (pMWin->eStart!=TK_UNBOUNDED||pMWin->eEnd!=TK_CURRENT||!pMWin->pOrderBy)
  ){
    int bCache = windowCachePartition(pMWin);
    if( (pMWin->eEnd!=TK_FOLLOWING   && pMWin->eEnd!=TK_PRECEDING) 
     || (pMWin->eStart!=TK_FOLLOWING && pMWin->eStart!=TK_PRECEDING) 
    ){
      VdbeModuleComment((pParse->pVdbe, "Begin RowExprStep()"));
      windowCodeRowExprStep(pParse, p, pWInfo, regGosub, addrGosub);
      VdbeModuleComment((pParse->pVdbe, "End RowExprStep()"));
    }else{
      VdbeModuleComment((pParse->pVdbe, "Begin windowCodeStep()"));
      windowCodeStep(pParse, p, pWInfo, regGosub, addrGosub);
      VdbeModuleComment((pParse->pVdbe, "End windowCodeStep()"));
    }
  }else{
    Window *pWin;
    int bCache = 0;               /* True to use CacheStep() */

    if( pMWin->eStart==TK_CURRENT && pMWin->eEnd==TK_UNBOUNDED ){
      bCache = 1;
    }else{







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    }
  }
  regArg = pParse->nMem+1;
  pParse->nMem += nArg;
  return regArg;
}














































































































































































































































































































/* 
** Return true if the entire partition should be cached in the ephemeral
** table before processing any rows.
*/
static int windowCachePartition(Window *pMWin){
  Window *pWin;
  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
................................................................................
static int windowCodeOp(
 WindowCodeArg *p,
 int op,
 int csr,
 int regCountdown,
 int jumpOnEof
){
  Window *pMWin = p->pMWin;
  int ret = 0;
  Vdbe *v = p->pVdbe;
  int addrIf = 0; 

  /* Special case - WINDOW_AGGINVERSE is always a no-op if the frame
  ** starts with UNBOUNDED PRECEDING. */
  if( op==WINDOW_AGGINVERSE && pMWin->eStart==TK_UNBOUNDED ){
    assert( regCountdown==0 && jumpOnEof==0 );
    return 0;
  }

  if( regCountdown>0 ){
    addrIf = sqlite3VdbeAddOp3(v, OP_IfPos, regCountdown, 0, 1);
  }

  switch( op ){
    case WINDOW_RETURN_ROW:
      windowAggFinal(p->pParse, pMWin, 0);
      windowReturnOneRow(p->pParse, pMWin, p->regGosub, p->addrGosub);
      break;

    case WINDOW_AGGINVERSE:
      windowAggStep(p->pParse, pMWin, csr, 1, p->regArg, pMWin->regSize);
      break;

    case WINDOW_AGGSTEP:
      windowAggStep(p->pParse, pMWin, csr, 0, p->regArg, pMWin->regSize);
      break;
  }

  if( jumpOnEof ){
    sqlite3VdbeAddOp2(v, OP_Next, csr, sqlite3VdbeCurrentAddr(v)+2);
    ret = sqlite3VdbeAddOp0(v, OP_Goto);
  }else{
................................................................................

  int regArg;
  int csrCurrent = pMWin->iEphCsr;
  int csrWrite = csrCurrent+1;
  int csrStart = csrCurrent+2;
  int csrEnd = csrCurrent+3;




  int iSubCsr = p->pSrc->a[0].iCursor;      /* Cursor of sub-select */
  int nSub = p->pSrc->a[0].pTab->nCol;      /* Number of cols returned by sub */
  int iCol;                                 /* To iterate through sub cols */

  int addrGoto;
  int addrIf;
................................................................................
  int addrCacheNext;

  int addrShortcut = 0;
  int addrEmpty = 0;

  int bCache = windowCachePartition(pMWin);

  int regStart = 0;               /* Value of <expr> PRECEDING */
  int regEnd = 0;                 /* Value of <expr> FOLLOWING */

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

  memset(&s, 0, sizeof(WindowCodeArg));
  s.pParse = pParse;
................................................................................
  s.pVdbe = v;
  s.regGosub = regGosub;
  s.addrGosub = addrGosub;

  pParse->nMem += 1 + nSub + 1;

  regFlushPart = ++pParse->nMem;

  if( pMWin->eStart==TK_PRECEDING || pMWin->eStart==TK_FOLLOWING ){
    regStart = ++pParse->nMem;
  }
  if( pMWin->eEnd==TK_PRECEDING || pMWin->eEnd==TK_FOLLOWING ){
    regEnd = ++pParse->nMem;
  }

  assert( pMWin->eStart==TK_PRECEDING 
       || pMWin->eStart==TK_CURRENT 
       || pMWin->eStart==TK_FOLLOWING 
       || pMWin->eStart==TK_UNBOUNDED 
  );
  assert( pMWin->eEnd==TK_FOLLOWING 
................................................................................
  }else{
    addrIf = sqlite3VdbeAddOp1(v, OP_IfNot, pMWin->regFirst);
  }

  /* This block is run for the first row of each partition */
  s.regArg = regArg = windowInitAccum(pParse, pMWin);

  if( regStart ){
    sqlite3ExprCode(pParse, pMWin->pStart, regStart);
    windowCheckIntValue(pParse, regStart, 0);
  }
  if( regEnd ){
    sqlite3ExprCode(pParse, pMWin->pEnd, regEnd);
    windowCheckIntValue(pParse, regEnd, 1);
  }

  if( pMWin->eStart==pMWin->eEnd && regStart && regEnd ){


    int op = ((pMWin->eStart==TK_FOLLOWING) ? OP_Ge : OP_Le);
    int addrGe = sqlite3VdbeAddOp3(v, op, regStart, 0, regEnd);
    windowAggFinal(pParse, pMWin, 0);
    if( bCache ){
      sqlite3VdbeAddOp2(v, OP_Rowid, csrWrite, regRowid);
      sqlite3VdbeAddOp3(v, OP_NotExists, csrCurrent, 0, regRowid);
      windowReturnOneRow(pParse, pMWin, regGosub, addrGosub);
................................................................................
      sqlite3VdbeAddOp2(v, OP_Rewind, csrCurrent, 1);
      windowReturnOneRow(pParse, pMWin, regGosub, addrGosub);
      sqlite3VdbeAddOp1(v, OP_ResetSorter, csrCurrent);
    }
    addrShortcut = sqlite3VdbeAddOp0(v, OP_Goto);
    sqlite3VdbeJumpHere(v, addrGe);
  }
  if( pMWin->eStart==TK_FOLLOWING && regEnd ){
    assert( pMWin->eEnd==TK_FOLLOWING );
    sqlite3VdbeAddOp3(v, OP_Subtract, regStart, regEnd, regStart);
  }

  if( pMWin->eStart!=TK_UNBOUNDED ){
    sqlite3VdbeAddOp2(v, OP_Rewind, csrStart, 1);
  }
  sqlite3VdbeAddOp2(v, OP_Rewind, csrCurrent, 1);
  sqlite3VdbeAddOp2(v, OP_Rewind, csrEnd, 1);

  sqlite3VdbeAddOp2(v, OP_Integer, 0, pMWin->regFirst);
  addrGoto = sqlite3VdbeAddOp0(v, OP_Goto);

  /* Begin generating SECOND_ROW_CODE */
................................................................................
  if( bCache ){
    addrCacheNext = sqlite3VdbeCurrentAddr(v);
  }else{
    sqlite3VdbeJumpHere(v, addrIf);
  }
  if( pMWin->eStart==TK_FOLLOWING ){
    windowCodeOp(&s, WINDOW_AGGSTEP, csrEnd, 0, 0);
    if( pMWin->eEnd!=TK_UNBOUNDED ){
      windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, regEnd, 0);
      windowCodeOp(&s, WINDOW_AGGINVERSE, csrStart, regStart, 0);
    }
  }else
  if( pMWin->eEnd==TK_PRECEDING ){
    windowCodeOp(&s, WINDOW_AGGSTEP, csrEnd, regEnd, 0);
    windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, 0, 0);
    windowCodeOp(&s, WINDOW_AGGINVERSE, csrStart, regStart, 0);
  }else{
    int addr;
    windowCodeOp(&s, WINDOW_AGGSTEP, csrEnd, 0, 0);
    if( pMWin->eEnd!=TK_UNBOUNDED ){
      if( regEnd ) addr = sqlite3VdbeAddOp3(v, OP_IfPos, regEnd, 0, 1);
      windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, 0, 0);
      windowCodeOp(&s, WINDOW_AGGINVERSE, csrStart, regStart, 0);
      if( regEnd ) sqlite3VdbeJumpHere(v, addr);
    }
  }
  VdbeModuleComment((pParse->pVdbe, "End windowCodeStep.SECOND_ROW_CODE"));

  /* End of the main input loop */
  sqlite3VdbeJumpHere(v, addrGoto);
  if( bCache ){
    sqlite3VdbeAddOp2(v, OP_Next, csrWrite, addrCacheNext);
................................................................................
    windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, 0, 0);
  }else if( pMWin->eStart==TK_FOLLOWING ){
    int addrStart;
    int addrBreak1;
    int addrBreak2;
    int addrBreak3;
    windowCodeOp(&s, WINDOW_AGGSTEP, csrEnd, 0, 0);
    if( pMWin->eEnd==TK_UNBOUNDED ){
      addrStart = sqlite3VdbeCurrentAddr(v);
      addrBreak1 = windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, regStart, 1);
      addrBreak2 = windowCodeOp(&s, WINDOW_AGGINVERSE, csrStart, 0, 1);
    }else{
      assert( pMWin->eEnd==TK_FOLLOWING );
      addrStart = sqlite3VdbeCurrentAddr(v);
      addrBreak1 = windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, regEnd, 1);
      addrBreak2 = windowCodeOp(&s, WINDOW_AGGINVERSE, csrStart, regStart, 1);
    }
    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrStart);
    sqlite3VdbeJumpHere(v, addrBreak2);
    addrStart = sqlite3VdbeCurrentAddr(v);
    addrBreak3 = windowCodeOp(&s, WINDOW_RETURN_ROW, csrCurrent, 0, 1);
    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrStart);
    sqlite3VdbeJumpHere(v, addrBreak1);
    sqlite3VdbeJumpHere(v, addrBreak3);
................................................................................
  **   RANGE BETWEEN CURRENT ROW AND CURRENT ROW 
  **   ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
  **
  ** windowCodeDefaultStep() is the only one of the three functions that
  ** does not cache each partition in a temp table before beginning to
  ** return rows.
  */
  if( pMWin->eType==TK_ROWS ){










    VdbeModuleComment((pParse->pVdbe, "Begin windowCodeStep()"));
    windowCodeStep(pParse, p, pWInfo, regGosub, addrGosub);
    VdbeModuleComment((pParse->pVdbe, "End windowCodeStep()"));

  }else{
    Window *pWin;
    int bCache = 0;               /* True to use CacheStep() */

    if( pMWin->eStart==TK_CURRENT && pMWin->eEnd==TK_UNBOUNDED ){
      bCache = 1;
    }else{