SQLite

      }
      if( !pColl ){
        pColl = pParse->db->pDfltColl;
      }
      if( regHit==0 && pAggInfo->nAccumulator ) regHit = ++pParse->nMem;
      sqlite3VdbeAddOp4(v, OP_CollSeq, regHit, 0, 0, (char *)pColl, P4_COLLSEQ);
    }
    sqlite3VdbeAddOp3(v, OP_AggStep0, 0, regAgg, pF->iMem);
    sqlite3VdbeAddOp3(v, OP_AggStep, 0, regAgg, pF->iMem);
    sqlite3VdbeAppendP4(v, pF->pFunc, P4_FUNCDEF);
    sqlite3VdbeChangeP5(v, (u8)nArg);
    sqlite3ExprCacheAffinityChange(pParse, regAgg, nArg);
    sqlite3ReleaseTempRange(pParse, regAgg, nArg);
    if( addrNext ){
      sqlite3VdbeResolveLabel(v, addrNext);
      sqlite3ExprCacheClear(pParse);

  if( pIn1->u.i>SMALLEST_INT64 ) pIn1->u.i--;
  VdbeBranchTaken(pIn1->u.i==0, 2);
  if( pIn1->u.i==0 ) goto jump_to_p2;
  break;
}


/* Opcode: AggStep0 P1 P2 P3 P4 P5
/* Opcode: AggStep * P2 P3 P4 P5
** Synopsis: accum=r[P3] step(r[P2@P5])
**
** Execute the xStep (if P1==0) or xInverse (if P1!=0) function for an
** aggregate.  The function has P5 arguments.  P4 is a pointer to the 
** Execute the xStep function for an aggregate.
** The function has P5 arguments.  P4 is a pointer to the 
** FuncDef structure that specifies the function.  Register P3 is the
** accumulator.
**
** The P5 arguments are taken from register P2 and its
** successors.
*/
/* Opcode: AggInverse * P2 P3 P4 P5
** Synopsis: accum=r[P3] inverse(r[P2@P5])
**
** Execute the xInverse function for an aggregate.
** The function has P5 arguments.  P4 is a pointer to the 
** FuncDef structure that specifies the function.  Register P3 is the
** accumulator.
**
** The P5 arguments are taken from register P2 and its
** successors.
*/
/* Opcode: AggStep P1 P2 P3 P4 P5
/* Opcode: AggStep1 P1 P2 P3 P4 P5
** Synopsis: accum=r[P3] step(r[P2@P5])
**
** Execute the xStep (if P1==0) or xInverse (if P1!=0) function for an
** aggregate.  The function has P5 arguments.  P4 is a pointer to the 
** FuncDef structure that specifies the function.  Register P3 is the
** accumulator.
**
** The P5 arguments are taken from register P2 and its
** successors.
**
** This opcode is initially coded as OP_AggStep0.  On first evaluation,
** the FuncDef stored in P4 is converted into an sqlite3_context and
** the opcode is changed.  In this way, the initialization of the
** sqlite3_context only happens once, instead of on each call to the
** step function.
*/
case OP_AggInverse:
case OP_AggStep0: {
case OP_AggStep: {
  int n;
  sqlite3_context *pCtx;

  assert( pOp->p4type==P4_FUNCDEF );
  n = pOp->p5;
  assert( pOp->p3>0 && pOp->p3<=(p->nMem+1 - p->nCursor) );
  assert( n==0 || (pOp->p2>0 && pOp->p2+n<=(p->nMem+1 - p->nCursor)+1) );

  pCtx->iOp = (int)(pOp - aOp);
  pCtx->pVdbe = p;
  pCtx->skipFlag = 0;
  pCtx->isError = 0;
  pCtx->argc = n;
  pOp->p4type = P4_FUNCCTX;
  pOp->p4.pCtx = pCtx;
  assert( pOp->p1==(pOp->opcode==OP_AggInverse) );
  pOp->opcode = OP_AggStep;
  pOp->opcode = OP_AggStep1;
  /* Fall through into OP_AggStep */
}
case OP_AggStep: {
case OP_AggStep1: {
  int i;
  sqlite3_context *pCtx;
  Mem *pMem;

  assert( pOp->p4type==P4_FUNCCTX );
  pCtx = pOp->p4.pCtx;
  pMem = &aMem[pOp->p3];

    if( rc ) goto abort_due_to_error;
  }
  assert( pCtx->pOut->flags==MEM_Null );
  assert( pCtx->skipFlag==0 );
  break;
}

/* Opcode: AggFinal P1 P2 P3 P4 *
/* Opcode: AggFinal P1 P2 * P4 *
** Synopsis: accum=r[P1] N=P2
**
** P1 is the memory location that is the accumulator for an aggregate
** or window function. If P3 is zero, then execute the finalizer function 
** for an aggregate and store the result in P1. Or, if P3 is non-zero,
** invoke the xValue() function and store the result in register P3.
** or window function.  Execute the finalizer function 
** for an aggregate and store the result in P1.
**
** P2 is the number of arguments that the step function takes and
** P4 is a pointer to the FuncDef for this function.  The P2
** argument is not used by this opcode.  It is only there to disambiguate
** functions that can take varying numbers of arguments.  The
** P4 argument is only needed for the case where
** the step function was not previously called.
*/
/* Opcode: AggValue * P2 P3 P4 *
** Synopsis: r[P3]=value N=P2
**
** Invoke the xValue() function and store the result in register P3.
**
** P2 is the number of arguments that the step function takes and
** P4 is a pointer to the FuncDef for this function.  The P2
** argument is not used by this opcode.  It is only there to disambiguate
** functions that can take varying numbers of arguments.  The
** P4 argument is only needed for the case where
** the step function was not previously called.
*/
case OP_AggValue:
case OP_AggFinal: {
  Mem *pMem;
  assert( pOp->p1>0 && pOp->p1<=(p->nMem+1 - p->nCursor) );
  assert( pOp->p3==0 || pOp->opcode==OP_AggValue );
  pMem = &aMem[pOp->p1];
  assert( (pMem->flags & ~(MEM_Null|MEM_Agg))==0 );
#ifndef SQLITE_OMIT_WINDOWFUNC
  if( pOp->p3 ){
    rc = sqlite3VdbeMemAggValue(pMem, &aMem[pOp->p3], pOp->p4.pFunc);
    pMem = &aMem[pOp->p3];
  }else
#endif
  {
  rc = sqlite3VdbeMemFinalize(pMem, pOp->p4.pFunc);
    rc = sqlite3VdbeMemFinalize(pMem, pOp->p4.pFunc);
  }
  
  if( rc ){
    sqlite3VdbeError(p, "%s", sqlite3_value_text(pMem));
    goto abort_due_to_error;
  }
  sqlite3VdbeChangeEncoding(pMem, encoding);
  UPDATE_MAX_BLOBSIZE(pMem);

  assert( pFunc->xValue!=0 );
  assert( (pAccum->flags & MEM_Null)!=0 || pFunc==pAccum->u.pDef );
  assert( pAccum->db==0 || sqlite3_mutex_held(pAccum->db->mutex) );
  memset(&ctx, 0, sizeof(ctx));
  memset(&t, 0, sizeof(t));
  t.flags = MEM_Null;
  t.db = pAccum->db;
  sqlite3VdbeMemSetNull(pOut);
  ctx.pOut = pOut;
  ctx.pMem = pAccum;
  ctx.pFunc = pFunc;
  pFunc->xValue(&ctx);
  return ctx.isError;
}
#endif /* SQLITE_OMIT_WINDOWFUNC */

** 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.
** array of registers before invoking OP_AggStep or OP_AggInverse
**
** 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.
*/

        }
      }
      if( pWin->pFunc->funcFlags & SQLITE_FUNC_NEEDCOLL ){
        CollSeq *pColl;
        pColl = sqlite3ExprNNCollSeq(pParse, pWin->pOwner->x.pList->a[0].pExpr);
        sqlite3VdbeAddOp4(v, OP_CollSeq, 0,0,0, (const char*)pColl, P4_COLLSEQ);
      }
      sqlite3VdbeAddOp3(v, bInverse? OP_AggInverse : OP_AggStep, 
      sqlite3VdbeAddOp3(v, OP_AggStep0, bInverse, regArg, pWin->regAccum);
                        bInverse, regArg, pWin->regAccum);
      sqlite3VdbeAppendP4(v, pWin->pFunc, P4_FUNCDEF);
      sqlite3VdbeChangeP5(v, (u8)nArg);
      if( addrIf ) sqlite3VdbeJumpHere(v, addrIf);
    }
  }
}

      sqlite3VdbeAddOp3(v, OP_Column, pWin->csrApp, 0, pWin->regResult);
      sqlite3VdbeJumpHere(v, sqlite3VdbeCurrentAddr(v)-2);
      if( bFinal ){
        sqlite3VdbeAddOp1(v, OP_ResetSorter, pWin->csrApp);
      }
    }else if( pWin->regApp ){
    }else{
      if( bFinal==0 ){
      if( bFinal ){
        sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regResult);
      }
      sqlite3VdbeAddOp2(v, OP_AggFinal, pWin->regAccum, windowArgCount(pWin));
      sqlite3VdbeAppendP4(v, pWin->pFunc, P4_FUNCDEF);
        sqlite3VdbeAddOp2(v, OP_AggFinal, pWin->regAccum, windowArgCount(pWin));
        sqlite3VdbeAppendP4(v, pWin->pFunc, P4_FUNCDEF);
      if( bFinal ){
        sqlite3VdbeAddOp2(v, OP_Copy, pWin->regAccum, pWin->regResult);
        sqlite3VdbeAddOp2(v, OP_Null, 0, pWin->regAccum);
      }else{
        sqlite3VdbeAddOp3(v, OP_AggValue, pWin->regAccum, windowArgCount(pWin),
        sqlite3VdbeChangeP3(v, -1, pWin->regResult);
                             pWin->regResult);
        sqlite3VdbeAppendP4(v, pWin->pFunc, P4_FUNCDEF);
      }
    }
  }
}

/*
** This function generates VM code to invoke the sub-routine at address

** from the Window.iEphCsr temp table. This routine generates VM code
** similar to:
**
**   while( regCtr>0 ){
**     regCtr--;
**     windowReturnOneRow()
**     if( bInverse ){
**       AggStep (xInverse)
**       AggInverse
**     }
**     Next (Window.iEphCsr)
**   }
*/
static void windowReturnRows(
  Parse *pParse,
  Window *pMWin,                  /* List of window functions */

**       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 ){
**           AggStep (csrStart, xInverse)
**           AggInverse (csrStart)
**           Next(csrStart)
**         }
**       }
**   flush_partition_done:
**     ResetSorter (csr)
**     Return
**

**       Aggstep (csrEnd)
**     }
**     while( 1 ){
**       AggFinal (xValue)
**       Gosub addrGosub
**       Next(csr)                     // if EOF goto flush_partition_done
**       if( (regStart--)<=0 ){
**         AggStep (csrStart, xInverse)
**         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).
**

**       while( 1 ){
**         regPeer++
**         Gosub addrGosub
**         Next(csr)                     // if EOF goto flush_partition_done
**         if( new peer ) break;
**       }
**       while( (regPeer--)>0 ){
**         AggStep (csrStart, xInverse)
**         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
**       }
**       AggStep (csrStart, xInverse)
**       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 ){
**       AggStep (csr2, xInverse)
**       AggInverse (csr2)
**       Next (csr2)
**     }
**
*/
static void windowCodeRowExprStep(
  Parse *pParse, 
  Select *p,

**
** RANGE BETWEEN CURRENT ROW AND CURRENT ROW 
**
**   As above, except that each of the for() loops becomes:
**
**         for(i=0; i<ctr; i++){
**           Gosub addrGosub
**           AggStep (xInverse, iEphCsr)
**           AggInverse (iEphCsr)
**           Next iEphCsr
**         }
**
** RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
**
**   flush_partition:
**     Once {

**     Rewind (csrLead)
**     Integer ctr 0
**     foreach row (csrLead){
**       if( new peer ){
**         AggFinal (xValue)
**         for(i=0; i<ctr; i++){
**           Gosub addrGosub
**           AggStep (xInverse, iEphCsr)
**           AggInverse (iEphCsr)
**           Next iEphCsr
**         }
**         Integer ctr 0
**       }
**       Incr ctr
**     }
**