}else{
    sqlite3WindowDelete(pParse->db, pWin);
  }
}

/*
** Return 0 if the two window objects are identical, or non-zero otherwise.

*/
int sqlite3WindowCompare(Parse *pParse, Window *p1, Window *p2){
  if( p1->eType!=p2->eType ) return 1;
  if( p1->eStart!=p2->eStart ) return 1;
  if( p1->eEnd!=p2->eEnd ) return 1;
  if( sqlite3ExprCompare(pParse, p1->pStart, p2->pStart, -1) ) return 1;
  if( sqlite3ExprCompare(pParse, p1->pEnd, p2->pEnd, -1) ) return 1;
  if( sqlite3ExprListCompare(p1->pPartition, p2->pPartition, -1) ) return 1;
  if( sqlite3ExprListCompare(p1->pOrderBy, p2->pOrderBy, -1) ) return 1;
  return 0;
}







static void windowAggInit(Parse *pParse, Window *pMWin){
  Window *pWin;
  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
    Vdbe *v = sqlite3GetVdbe(pParse);









    FuncDef *p = pWin->pFunc;
    if( (p->funcFlags & SQLITE_FUNC_MINMAX) && pWin->eStart!=TK_UNBOUNDED ){
      ExprList *pList = pWin->pOwner->x.pList;
      KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pList, 0, 0);
      pWin->csrApp = pParse->nTab++;
      pWin->regApp = pParse->nMem+1;
      pParse->nMem += 3;
................................................................................
      assert( pMWin->iEphCsr );
      pWin->csrApp = pParse->nTab++;
      sqlite3VdbeAddOp2(v, OP_OpenDup, pWin->csrApp, pMWin->iEphCsr);
    }
  }
}

void sqlite3WindowCodeInit(Parse *pParse, Window *pWin){

  Vdbe *v = sqlite3GetVdbe(pParse);
  int nPart = (pWin->pPartition ? pWin->pPartition->nExpr : 0);
  nPart += (pWin->pOrderBy ? pWin->pOrderBy->nExpr : 0);
  if( nPart ){
    pWin->regPart = pParse->nMem+1;
    pParse->nMem += nPart;
    sqlite3VdbeAddOp3(v, OP_Null, 0, pWin->regPart, pWin->regPart+nPart-1);
  }
  windowAggInit(pParse, pWin);
}


static void windowCheckFrameValue(Parse *pParse, int reg, int bEnd){
  static const char *azErr[] = {
    "frame starting offset must be a non-negative integer",
    "frame ending offset must be a non-negative integer"
  };
  Vdbe *v = sqlite3GetVdbe(pParse);
  int regZero = ++pParse->nMem;

  sqlite3VdbeAddOp2(v, OP_Integer, 0, regZero);
  sqlite3VdbeAddOp2(v, OP_MustBeInt, reg, sqlite3VdbeCurrentAddr(v)+2);
  sqlite3VdbeAddOp3(v, OP_Ge, regZero, sqlite3VdbeCurrentAddr(v)+2, reg);
  sqlite3VdbeAddOp2(v, OP_Halt, SQLITE_ERROR, OE_Abort);
  sqlite3VdbeAppendP4(v, (void*)azErr[bEnd], P4_STATIC);

}





static int windowArgCount(Window *pWin){
  ExprList *pList = pWin->pOwner->x.pList;
  return (pList ? pList->nExpr : 0);
}

/*
** Generate VM code to invoke either xStep() (if bInverse is 0) or 
** xInverse (if bInverse is non-zero) for each window function in the 
** linked list starting at pMWin.














*/
static void windowAggStep(
  Parse *pParse, 
  Window *pMWin, 
  int csr,
  int bInverse, 
  int reg,




  int regPartSize                 /* Register containing size of partition */
){
  Vdbe *v = sqlite3GetVdbe(pParse);
  Window *pWin;
  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
    int flags = pWin->pFunc->funcFlags;
    int regArg;
................................................................................
      sqlite3VdbeAppendP4(v, pWin->pFunc, P4_FUNCDEF);
      sqlite3VdbeChangeP5(v, (u8)nArg);
      if( addrIf ) sqlite3VdbeJumpHere(v, addrIf);
    }
  }
}







static void windowAggFinal(Parse *pParse, Window *pMWin, int bFinal){
  Vdbe *v = sqlite3GetVdbe(pParse);
  Window *pWin;

  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
    if( (pWin->pFunc->funcFlags & SQLITE_FUNC_MINMAX) 
     && pWin->eStart!=TK_UNBOUNDED 
................................................................................
      }else{
        sqlite3VdbeChangeP3(v, -1, pWin->regResult);
      }
    }
  }
}






static void windowPartitionCache(
  Parse *pParse,
  Select *p,

  WhereInfo *pWInfo,
  int regFlushPart,
  int lblFlushPart,
  int *pRegSize

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

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














static void windowReturnOneRow(
  Parse *pParse,
  Window *pMWin,
  int regGosub,
  int addrGosub
){
  Vdbe *v = sqlite3GetVdbe(pParse);
................................................................................
      sqlite3VdbeResolveLabel(v, lbl);
      sqlite3ReleaseTempReg(pParse, tmpReg);
    }
  }
  sqlite3VdbeAddOp2(v, OP_Gosub, regGosub, addrGosub);
}

static void windowReturnRows(
  Parse *pParse,
  Window *pMWin,
  int regCtr,
  int bFinal,
  int regGosub,
  int addrGosub,
  int regInvArg,
  int regInvSize














){
  int addr;
  Vdbe *v = sqlite3GetVdbe(pParse);
  windowAggFinal(pParse, pMWin, 0);
  addr = sqlite3VdbeAddOp3(v, OP_IfPos, regCtr, sqlite3VdbeCurrentAddr(v)+2 ,1);
  sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
  windowReturnOneRow(pParse, pMWin, regGosub, addrGosub);
................................................................................
  int addrIfPos1;
  int addrIfPos2;

  int regPeer = 0;                 /* Number of peers in current group */
  int regPeerVal = 0;              /* Array of values identifying peer group */
  int iPeer = 0;                   /* Column offset in eph-table of peer vals */
  int nPeerVal;                    /* Number of peer values */
  int bRange = 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 
  );

  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;
................................................................................

  if( pMWin->eEnd==TK_FOLLOWING ){
    addrIfPos1 = sqlite3VdbeAddOp3(v, OP_IfPos, regEnd, 0 , 1);
  }
  if( pMWin->eStart==TK_FOLLOWING ){
    addrIfPos2 = sqlite3VdbeAddOp3(v, OP_IfPos, regStart, 0 , 1);
  }
  if( bRange ){
    assert( pMWin->eStart==TK_CURRENT && pMWin->pOrderBy );
    regPeer = ++pParse->nMem;
    regPeerVal = pParse->nMem+1;
    iPeer = pMWin->nBufferCol + (pMWin->pPartition?pMWin->pPartition->nExpr:0);
    nPeerVal = pMWin->pOrderBy->nExpr;
    pParse->nMem += (2 * nPeerVal);
    for(k=0; k<nPeerVal; k++){
      sqlite3VdbeAddOp3(v, OP_Column, pMWin->iEphCsr, iPeer+k, regPeerVal+k);
    }
    sqlite3VdbeAddOp2(v, OP_Integer, 0, regPeer);
  }

  windowAggFinal(pParse, pMWin, 0);
  if( bRange ){
    sqlite3VdbeAddOp2(v, OP_AddImm, regPeer, 1);
  }
  windowReturnOneRow(pParse, pMWin, regGosub, addrGosub);
  sqlite3VdbeAddOp2(v, OP_Next, pMWin->iEphCsr, sqlite3VdbeCurrentAddr(v)+2);
  sqlite3VdbeAddOp2(v, OP_Goto, 0, lblFlushDone);
  if( bRange ){
    KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pMWin->pOrderBy,0,0);
    int addrJump = sqlite3VdbeCurrentAddr(v)-4;
    for(k=0; k<nPeerVal; k++){
      int iOut = regPeerVal + nPeerVal + k;
      sqlite3VdbeAddOp3(v, OP_Column, pMWin->iEphCsr, iPeer+k, iOut);
    }
    sqlite3VdbeAddOp3(v, OP_Compare, regPeerVal, regPeerVal+nPeerVal, nPeerVal);
    sqlite3VdbeAppendP4(v, (void*)pKeyInfo, P4_KEYINFO);
    addr = sqlite3VdbeCurrentAddr(v)+1;
    sqlite3VdbeAddOp3(v, OP_Jump, addr, addrJump, addr);
  }
  if( pMWin->eStart==TK_FOLLOWING ){
    sqlite3VdbeJumpHere(v, addrIfPos2);
  }

  if( pMWin->eStart==TK_CURRENT 
   || pMWin->eStart==TK_PRECEDING 
   || pMWin->eStart==TK_FOLLOWING 
  ){
    int addrJumpHere = 0;
    if( pMWin->eStart==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, regSize);
    if( bRange ){
      sqlite3VdbeAddOp2(v, OP_Goto, 0, addrJumpHere-1);
    }
    if( addrJumpHere ){
      sqlite3VdbeJumpHere(v, addrJumpHere);
    }
  }
  if( pMWin->eEnd==TK_FOLLOWING ){
    sqlite3VdbeJumpHere(v, addrIfPos1);
  }
................................................................................
**
**     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
................................................................................
  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 regSize;
  int nArg;



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

................................................................................
  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 */
  regArg = windowInitAccum(pParse, pMWin);

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









  if( pOrderBy && pMWin->eEnd==TK_CURRENT ){
    int bCurrent = (pMWin->eEnd==TK_CURRENT && pMWin->eStart==TK_CURRENT);
    int addrJump = 0;             /* Address of OP_Jump below */
    if( pMWin->eType==TK_RANGE ){
      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);
    }

    windowReturnRows(pParse, pMWin, regCtr, 0, regGosub, addrGosub, 
        (bCurrent ? regArg : 0), (bCurrent ? regSize : 0)
    );
    if( addrJump ) sqlite3VdbeJumpHere(v, addrJump);
  }


  windowAggStep(pParse, pMWin, csrLead, 0, regArg, regSize);

  sqlite3VdbeAddOp2(v, OP_AddImm, regCtr, 1);
  sqlite3VdbeAddOp2(v, OP_Next, csrLead, addrRewind+2);

  windowReturnRows(pParse, pMWin, regCtr, 1, regGosub, addrGosub, 0, 0);

  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);
}

................................................................................

  windowAggFinal(pParse, pMWin, 1);
  sqlite3VdbeAddOp2(v, OP_Rewind, pMWin->iEphCsr,sqlite3VdbeCurrentAddr(v)+3);
  sqlite3VdbeAddOp2(v, OP_Gosub, regGosub, addrGosub);
  sqlite3VdbeAddOp2(v, OP_Next, pMWin->iEphCsr, sqlite3VdbeCurrentAddr(v)-1);
}






Window *sqlite3WindowDup(sqlite3 *db, Expr *pOwner, Window *p){
  Window *pNew = 0;
  if( p ){
    pNew = sqlite3DbMallocZero(db, sizeof(Window));
    if( pNew ){
      pNew->pFilter = sqlite3ExprDup(db, p->pFilter, 0);
      pNew->pPartition = sqlite3ExprListDup(db, p->pPartition, 0);
................................................................................
  Parse *pParse,                  /* Parse context */
  Select *p,                      /* Rewritten SELECT statement */
  WhereInfo *pWInfo,              /* Context returned by sqlite3WhereBegin() */
  int regGosub,                   /* Register for OP_Gosub */
  int addrGosub                   /* OP_Gosub here to return each row */
){
  Window *pMWin = p->pWin;
  Window *pWin;

  /* Call windowCodeRowExprStep() for all window modes *except*:
  **
  **   RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
  **   RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
  **   RANGE BETWEEN CURRENT ROW AND CURRENT ROW
  **   ROWS  BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
  */
  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;



  }




  /* Call windowCodeCacheStep() if there is a window function that requires
  ** that the entire partition be cached in a temp table before any rows
  ** are returned.  */
  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
    FuncDef *pFunc = pWin->pFunc;
    if( (pFunc->funcFlags & SQLITE_FUNC_WINDOW_SIZE)
     || (pFunc->xSFunc==nth_valueStepFunc)
     || (pFunc->xSFunc==first_valueStepFunc)
     || (pFunc->xSFunc==leadStepFunc)
     || (pFunc->xSFunc==lagStepFunc)
    ){
      windowCodeCacheStep(pParse, p, pWInfo, regGosub, addrGosub);
      return;
    }
  }


  /* Otherwise, call windowCodeDefaultStep().  */



  windowCodeDefaultStep(pParse, p, pWInfo, regGosub, addrGosub);
}

  }else{
    sqlite3WindowDelete(pParse->db, pWin);
  }
}

/*
** Return 0 if the two window objects are identical, or non-zero otherwise.
** Identical window objects can be processed in a single scan.
*/
int sqlite3WindowCompare(Parse *pParse, Window *p1, Window *p2){
  if( p1->eType!=p2->eType ) return 1;
  if( p1->eStart!=p2->eStart ) return 1;
  if( p1->eEnd!=p2->eEnd ) return 1;
  if( sqlite3ExprCompare(pParse, p1->pStart, p2->pStart, -1) ) return 1;
  if( sqlite3ExprCompare(pParse, p1->pEnd, p2->pEnd, -1) ) return 1;
  if( sqlite3ExprListCompare(p1->pPartition, p2->pPartition, -1) ) return 1;
  if( sqlite3ExprListCompare(p1->pOrderBy, p2->pOrderBy, -1) ) return 1;
  return 0;
}


/*
** This is called by code in select.c before it calls sqlite3WhereBegin()
** to begin iterating through the sub-query results. It is used to allocate
** and initialize registers and cursors used by sqlite3WindowCodeStep().
*/
void sqlite3WindowCodeInit(Parse *pParse, Window *pMWin){
  Window *pWin;

  Vdbe *v = sqlite3GetVdbe(pParse);
  int nPart = (pMWin->pPartition ? pMWin->pPartition->nExpr : 0);
  nPart += (pMWin->pOrderBy ? pMWin->pOrderBy->nExpr : 0);
  if( nPart ){
    pMWin->regPart = pParse->nMem+1;
    pParse->nMem += nPart;
    sqlite3VdbeAddOp3(v, OP_Null, 0, pMWin->regPart, pMWin->regPart+nPart-1);
  }

  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
    FuncDef *p = pWin->pFunc;
    if( (p->funcFlags & SQLITE_FUNC_MINMAX) && pWin->eStart!=TK_UNBOUNDED ){
      ExprList *pList = pWin->pOwner->x.pList;
      KeyInfo *pKeyInfo = sqlite3KeyInfoFromExprList(pParse, pList, 0, 0);
      pWin->csrApp = pParse->nTab++;
      pWin->regApp = pParse->nMem+1;
      pParse->nMem += 3;
................................................................................
      assert( pMWin->iEphCsr );
      pWin->csrApp = pParse->nTab++;
      sqlite3VdbeAddOp2(v, OP_OpenDup, pWin->csrApp, pMWin->iEphCsr);
    }
  }
}


/*
** A "PRECEDING <expr>" (bEnd==0) or "FOLLOWING <expr>" (bEnd==1) has just 
** been evaluated and the result left in register reg. This function generates
** VM code to check that the value is a non-negative integer and throws
** an exception if it is not.







*/
static void windowCheckFrameValue(Parse *pParse, int reg, int bEnd){
  static const char *azErr[] = {
    "frame starting offset must be a non-negative integer",
    "frame ending offset must be a non-negative integer"
  };
  Vdbe *v = sqlite3GetVdbe(pParse);
  int regZero = sqlite3GetTempReg(pParse);

  sqlite3VdbeAddOp2(v, OP_Integer, 0, regZero);
  sqlite3VdbeAddOp2(v, OP_MustBeInt, reg, sqlite3VdbeCurrentAddr(v)+2);
  sqlite3VdbeAddOp3(v, OP_Ge, regZero, sqlite3VdbeCurrentAddr(v)+2, reg);
  sqlite3VdbeAddOp2(v, OP_Halt, SQLITE_ERROR, OE_Abort);
  sqlite3VdbeAppendP4(v, (void*)azErr[bEnd], P4_STATIC);
  sqlite3ReleaseTempReg(pParse, regZero);
}

/*
** Return the number of arguments passed to the window-function associated
** with the object passed as the only argument to this function.
*/
static int windowArgCount(Window *pWin){
  ExprList *pList = pWin->pOwner->x.pList;
  return (pList ? pList->nExpr : 0);
}

/*
** Generate VM code to invoke either xStep() (if bInverse is 0) or 
** xInverse (if bInverse is non-zero) for each window function in the 
** linked list starting at pMWin. Or, for built-in window functions
** that do not use the standard function API, generate the required
** inline VM code.
**
** If argument csr is greater than or equal to 0, then argument reg is
** the first register in an array of registers guaranteed to be large
** enough to hold the array of arguments for each function. In this case
** the arguments are extracted from the current row of csr into the
** array of registers before invoking OP_AggStep.
**
** Or, if csr is less than zero, then the array of registers at reg is
** already populated with all columns from the current row of the sub-query.
**
** If argument regPartSize is non-zero, then it is a register containing the
** number of rows in the current partition.
*/
static void windowAggStep(
  Parse *pParse, 




  Window *pMWin,                  /* Linked list of window functions */
  int csr,                        /* Read arguments from this cursor */
  int bInverse,                   /* True to invoke xInverse instead of xStep */
  int reg,                        /* Array of registers */
  int regPartSize                 /* Register containing size of partition */
){
  Vdbe *v = sqlite3GetVdbe(pParse);
  Window *pWin;
  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
    int flags = pWin->pFunc->funcFlags;
    int regArg;
................................................................................
      sqlite3VdbeAppendP4(v, pWin->pFunc, P4_FUNCDEF);
      sqlite3VdbeChangeP5(v, (u8)nArg);
      if( addrIf ) sqlite3VdbeJumpHere(v, addrIf);
    }
  }
}

/*
** Generate VM code to invoke either xValue() (bFinal==0) or xFinalize()
** (bFinal==1) for each window function in the linked list starting at
** pMWin. Or, for built-in window-functions that do not use the standard
** API, generate the equivalent VM code.
*/
static void windowAggFinal(Parse *pParse, Window *pMWin, int bFinal){
  Vdbe *v = sqlite3GetVdbe(pParse);
  Window *pWin;

  for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
    if( (pWin->pFunc->funcFlags & SQLITE_FUNC_MINMAX) 
     && pWin->eStart!=TK_UNBOUNDED 
................................................................................
      }else{
        sqlite3VdbeChangeP3(v, -1, pWin->regResult);
      }
    }
  }
}

/*
** This function generates VM code to invoke the sub-routine at address
** lblFlushPart once for each partition with the entire partition cached in
** the Window.iEphCsr temp table.
*/
static void windowPartitionCache(
  Parse *pParse,

  Select *p,                      /* The rewritten SELECT statement */
  WhereInfo *pWInfo,              /* WhereInfo to call WhereEnd() on */
  int regFlushPart,               /* Register to use with Gosub lblFlushPart */
  int lblFlushPart,               /* Subroutine to Gosub to */

  int *pRegSize                   /* OUT: Register containing partition size */
){
  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;
................................................................................
  /* End of the input loop */
  sqlite3WhereEnd(pWInfo);

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

/*
** Invoke the sub-routine at regGosub (generated by code in select.c) to
** return the current row of Window.iEphCsr. If all window functions are
** aggregate window functions that use the standard API, a single
** OP_Gosub instruction is all that this routine generates. Extra VM code
** for per-row processing is only generated for the following built-in window
** functions:
**
**   nth_value()
**   first_value()
**   lag()
**   lead()
*/
static void windowReturnOneRow(
  Parse *pParse,
  Window *pMWin,
  int regGosub,
  int addrGosub
){
  Vdbe *v = sqlite3GetVdbe(pParse);
................................................................................
      sqlite3VdbeResolveLabel(v, lbl);
      sqlite3ReleaseTempReg(pParse, tmpReg);
    }
  }
  sqlite3VdbeAddOp2(v, OP_Gosub, regGosub, addrGosub);
}

/*
** Invoke the code generated by windowReturnOneRow() and, optionally, the
** xInverse() function for each window function, for one or more rows
** from the Window.iEphCsr temp table. This routine generates VM code
** similar to:
**
**   while( regCtr>0 ){
**     regCtr--;
**     windowReturnOneRow()
**     if( bInverse ){
**       AggStep (xInverse)
**     }
**     Next (Window.iEphCsr)
**   }
*/
static void windowReturnRows(
  Parse *pParse,
  Window *pMWin,                  /* List of window functions */
  int regCtr,                     /* Register containing number of rows */
  int regGosub,                   /* Register for Gosub addrGosub */
  int addrGosub,                  /* Address of sub-routine for ReturnOneRow */
  int regInvArg,                  /* Array of registers for xInverse args */
  int regInvSize                  /* Register containing size of partition */
){
  int addr;
  Vdbe *v = sqlite3GetVdbe(pParse);
  windowAggFinal(pParse, pMWin, 0);
  addr = sqlite3VdbeAddOp3(v, OP_IfPos, regCtr, sqlite3VdbeCurrentAddr(v)+2 ,1);
  sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
  windowReturnOneRow(pParse, pMWin, regGosub, addrGosub);
................................................................................
  int addrIfPos1;
  int addrIfPos2;

  int regPeer = 0;                 /* Number of peers in current group */
  int regPeerVal = 0;              /* Array of values identifying peer group */
  int iPeer = 0;                   /* Column offset in eph-table of peer vals */
  int nPeerVal;                    /* Number of peer values */

  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(v);
  lblFlushDone = sqlite3VdbeMakeLabel(v);

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

  if( pMWin->eEnd==TK_FOLLOWING ){
    addrIfPos1 = sqlite3VdbeAddOp3(v, OP_IfPos, regEnd, 0 , 1);
  }
  if( pMWin->eStart==TK_FOLLOWING ){
    addrIfPos2 = sqlite3VdbeAddOp3(v, OP_IfPos, regStart, 0 , 1);
  }













  windowAggFinal(pParse, pMWin, 0);



  windowReturnOneRow(pParse, pMWin, regGosub, addrGosub);
  sqlite3VdbeAddOp2(v, OP_Next, pMWin->iEphCsr, sqlite3VdbeCurrentAddr(v)+2);
  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 addrJumpHere = 0;
    if( pMWin->eStart==TK_PRECEDING ){
      addrJumpHere = sqlite3VdbeAddOp3(v, OP_IfPos, regStart, 0 , 1);
    }




    sqlite3VdbeAddOp2(v, OP_Next, csrStart, sqlite3VdbeCurrentAddr(v)+1);
    windowAggStep(pParse, pMWin, csrStart, 1, regArg, regSize);



    if( addrJumpHere ){
      sqlite3VdbeJumpHere(v, addrJumpHere);
    }
  }
  if( pMWin->eEnd==TK_FOLLOWING ){
    sqlite3VdbeJumpHere(v, addrIfPos1);
  }
................................................................................
**
**     ResetSorter (csr)
**     Return
**
** ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
** RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
** RANGE BETWEEN CURRENT ROW AND CURRENT ROW 


*/
static void windowCodeCacheStep(
  Parse *pParse, 
  Select *p,
  WhereInfo *pWInfo,
  int regGosub, 
  int addrGosub
................................................................................
  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 addrNext;                   /* Jump here for next iteration of loop */
  int regFlushPart;
  int lblFlushPart;
  int csrLead;
  int regCtr;
  int regArg;                     /* Register array to martial function args */
  int regSize;
  int nArg;
  int bReverse;
  int lblEmpty;

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

  lblEmpty = sqlite3VdbeMakeLabel(v);
  bReverse = (pMWin->eStart==TK_CURRENT && pMWin->eEnd==TK_UNBOUNDED);
  regNewPeer = pParse->nMem+1;
  pParse->nMem += nPeer;

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

................................................................................
  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 */
  regArg = windowInitAccum(pParse, pMWin);

  sqlite3VdbeAddOp2(v, OP_Integer, 0, regCtr);
  sqlite3VdbeAddOp2(v, OP_Rewind, csrLead, lblEmpty);
  sqlite3VdbeAddOp2(v, OP_Rewind, pMWin->iEphCsr, lblEmpty);

  if( bReverse ){
    int addr = sqlite3VdbeCurrentAddr(v);
    windowAggStep(pParse, pMWin, csrLead, 0, regArg, regSize);
    sqlite3VdbeAddOp2(v, OP_Next, csrLead, addr);
    sqlite3VdbeAddOp2(v, OP_Rewind, csrLead, lblEmpty);
  }
  addrNext = sqlite3VdbeCurrentAddr(v);

  if( pOrderBy && (pMWin->eEnd==TK_CURRENT || pMWin->eStart==TK_CURRENT) ){
    int bCurrent = (pMWin->eStart==TK_CURRENT);
    int addrJump = 0;             /* Address of OP_Jump below */
    if( pMWin->eType==TK_RANGE ){
      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);
    }

    windowReturnRows(pParse, pMWin, regCtr, regGosub, addrGosub, 
        (bCurrent ? regArg : 0), (bCurrent ? regSize : 0)
    );
    if( addrJump ) sqlite3VdbeJumpHere(v, addrJump);
  }

  if( bReverse==0 ){
    windowAggStep(pParse, pMWin, csrLead, 0, regArg, regSize);
  }
  sqlite3VdbeAddOp2(v, OP_AddImm, regCtr, 1);
  sqlite3VdbeAddOp2(v, OP_Next, csrLead, addrNext);

  windowReturnRows(pParse, pMWin, regCtr, regGosub, addrGosub, 0, 0);



  sqlite3VdbeResolveLabel(v, lblEmpty);
  sqlite3VdbeAddOp1(v, OP_ResetSorter, pMWin->iEphCsr);
  sqlite3VdbeAddOp1(v, OP_Return, regFlushPart);

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

................................................................................

  windowAggFinal(pParse, pMWin, 1);
  sqlite3VdbeAddOp2(v, OP_Rewind, pMWin->iEphCsr,sqlite3VdbeCurrentAddr(v)+3);
  sqlite3VdbeAddOp2(v, OP_Gosub, regGosub, addrGosub);
  sqlite3VdbeAddOp2(v, OP_Next, pMWin->iEphCsr, sqlite3VdbeCurrentAddr(v)-1);
}

/*
** Allocate and return a duplicate of the Window object indicated by the
** third argument. Set the Window.pOwner field of the new object to
** pOwner.
*/
Window *sqlite3WindowDup(sqlite3 *db, Expr *pOwner, Window *p){
  Window *pNew = 0;
  if( p ){
    pNew = sqlite3DbMallocZero(db, sizeof(Window));
    if( pNew ){
      pNew->pFilter = sqlite3ExprDup(db, p->pFilter, 0);
      pNew->pPartition = sqlite3ExprListDup(db, p->pPartition, 0);
................................................................................
  Parse *pParse,                  /* Parse context */
  Select *p,                      /* Rewritten SELECT statement */
  WhereInfo *pWInfo,              /* Context returned by sqlite3WhereBegin() */
  int regGosub,                   /* Register for OP_Gosub */
  int addrGosub                   /* OP_Gosub here to return each row */
){
  Window *pMWin = p->pWin;
  ExprList *pOrderBy = pMWin->pOrderBy;

  /* Call windowCodeRowExprStep() for all "ROWS" window modes except:
  **
  **   ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW



  */
  if( (pMWin->eType==TK_ROWS 
   && (pMWin->eStart!=TK_UNBOUNDED || pMWin->eEnd!=TK_CURRENT || !pOrderBy))

  ){
    windowCodeRowExprStep(pParse, p, pWInfo, regGosub, addrGosub);

  }else{
    Window *pWin;
    int bCache = 0;


    if( pMWin->eStart==TK_CURRENT && pMWin->eEnd==TK_UNBOUNDED && pOrderBy ){
      bCache = 1;
    }else{
      /* Call windowCodeCacheStep() if there is a window function that requires
      ** that the entire partition be cached in a temp table before any rows
      ** are returned.  */
      for(pWin=pMWin; pWin; pWin=pWin->pNextWin){
        FuncDef *pFunc = pWin->pFunc;
        if( (pFunc->funcFlags & SQLITE_FUNC_WINDOW_SIZE)
            || (pFunc->xSFunc==nth_valueStepFunc)
            || (pFunc->xSFunc==first_valueStepFunc)
            || (pFunc->xSFunc==leadStepFunc)
            || (pFunc->xSFunc==lagStepFunc)
          ){
          bCache = 1;
          break;
        }
      }
    }

    /* Otherwise, call windowCodeDefaultStep().  */
    if( bCache ){
      windowCodeCacheStep(pParse, p, pWInfo, regGosub, addrGosub);
    }else{
      windowCodeDefaultStep(pParse, p, pWInfo, regGosub, addrGosub);
    }
  }
}

execsql_test 4.2 {
  SELECT max(b) OVER (ORDER BY max(c)) FROM ttt GROUP BY b;
}

execsql_test 4.3 {
  SELECT abs(max(b) OVER (ORDER BY b)) FROM ttt GROUP BY b;
}








finish_test

execsql_test 4.2 {
  SELECT max(b) OVER (ORDER BY max(c)) FROM ttt GROUP BY b;
}

execsql_test 4.3 {
  SELECT abs(max(b) OVER (ORDER BY b)) FROM ttt GROUP BY b;
}

execsql_test 4.4 {
  SELECT sum(b) OVER (
    ORDER BY a RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING
  ) FROM ttt;
}


finish_test

  SELECT max(b) OVER (ORDER BY max(c)) FROM ttt GROUP BY b;
} {1   2   3}

do_execsql_test 4.3 {
  SELECT abs(max(b) OVER (ORDER BY b)) FROM ttt GROUP BY b;
} {1   2   3}







finish_test

  SELECT max(b) OVER (ORDER BY max(c)) FROM ttt GROUP BY b;
} {1   2   3}

do_execsql_test 4.3 {
  SELECT abs(max(b) OVER (ORDER BY b)) FROM ttt GROUP BY b;
} {1   2   3}

do_execsql_test 4.4 {
  SELECT sum(b) OVER (
    ORDER BY a RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING
  ) FROM ttt;
} {18   17   15   12   11   9   6   5   3}

finish_test