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Reduce memory requirements for ORDER BY combined with LIMIT. Ticket #1586. (CVS 2887)

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FossilOrigin-Name: 55e703ecac6e03d7364c2d919ba18d7293d6b7f6
This commit is contained in:
drh
2006-01-08 05:02:54 +00:00
parent 76873ab240
commit d59ba6ce61
3 changed files with 42 additions and 17 deletions
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45
src/select.c
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@@ -12,7 +12,7 @@
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.286 2006/01/07 13:21:04 danielk1977 Exp $
** $Id: select.c,v 1.287 2006/01/08 05:02:55 drh Exp $
*/
#include "sqliteInt.h"
@@ -351,12 +351,28 @@ void sqlite3SelectDelete(Select *p){
** Insert code into "v" that will push the record on the top of the
** stack into the sorter.
*/
static void pushOntoSorter(Parse *pParse, Vdbe *v, ExprList *pOrderBy){
static void pushOntoSorter(
Parse *pParse, /* Parser context */
ExprList *pOrderBy, /* The ORDER BY clause */
Select *pSelect /* The whole SELECT statement */
){
Vdbe *v = pParse->pVdbe;
sqlite3ExprCodeExprList(pParse, pOrderBy);
sqlite3VdbeAddOp(v, OP_Sequence, pOrderBy->iECursor, 0);
sqlite3VdbeAddOp(v, OP_Pull, pOrderBy->nExpr + 1, 0);
sqlite3VdbeAddOp(v, OP_MakeRecord, pOrderBy->nExpr + 2, 0);
sqlite3VdbeAddOp(v, OP_IdxInsert, pOrderBy->iECursor, 0);
if( pSelect->iLimit>=0 ){
int addr1;
sqlite3VdbeAddOp(v, OP_MemIncr, pSelect->iLimit+1, 0);
addr1 = sqlite3VdbeAddOp(v, OP_IfMemPos, pSelect->iLimit+1, 0);
sqlite3VdbeAddOp(v, OP_Goto, 0, 0);
sqlite3VdbeJumpHere(v, addr1);
sqlite3VdbeAddOp(v, OP_Last, pOrderBy->iECursor, 0);
sqlite3VdbeAddOp(v, OP_Delete, pOrderBy->iECursor, 0);
sqlite3VdbeJumpHere(v, addr1+1);
pSelect->iLimit = -1;
}
}
/*
@@ -504,7 +520,7 @@ static int selectInnerLoop(
case SRT_VirtualTab: {
sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
if( pOrderBy ){
pushOntoSorter(pParse, v, pOrderBy);
pushOntoSorter(pParse, pOrderBy, p);
}else{
sqlite3VdbeAddOp(v, OP_NewRowid, iParm, 0);
sqlite3VdbeAddOp(v, OP_Pull, 1, 0);
@@ -531,7 +547,7 @@ static int selectInnerLoop(
** 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, v, pOrderBy);
pushOntoSorter(pParse, pOrderBy, p);
}else{
char aff = (iParm>>16)&0xFF;
aff = sqlite3CompareAffinity(pEList->a[0].pExpr, aff);
@@ -558,7 +574,7 @@ static int selectInnerLoop(
case SRT_Mem: {
assert( nColumn==1 );
if( pOrderBy ){
pushOntoSorter(pParse, v, pOrderBy);
pushOntoSorter(pParse, pOrderBy, p);
}else{
sqlite3VdbeAddOp(v, OP_MemStore, iParm, 1);
/* The LIMIT clause will jump out of the loop for us */
@@ -575,7 +591,7 @@ static int selectInnerLoop(
case SRT_Callback: {
if( pOrderBy ){
sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
pushOntoSorter(pParse, v, pOrderBy);
pushOntoSorter(pParse, pOrderBy, p);
}else if( eDest==SRT_Subroutine ){
sqlite3VdbeAddOp(v, OP_Gosub, 0, iParm);
}else{
@@ -1358,7 +1374,7 @@ Vdbe *sqlite3GetVdbe(Parse *pParse){
** the limit and offset. If there is no limit and/or offset, then
** iLimit and iOffset are negative.
**
** This routine changes the values if iLimit and iOffset only if
** This routine changes the values of iLimit and iOffset only if
** a limit or offset is defined by pLimit and pOffset. iLimit and
** iOffset should have been preset to appropriate default values
** (usually but not always -1) prior to calling this routine.
@@ -1375,13 +1391,14 @@ static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
** no rows.
*/
if( p->pLimit ){
int iMem = pParse->nMem++;
int iMem = pParse->nMem;
pParse->nMem += 2;
Vdbe *v = sqlite3GetVdbe(pParse);
if( v==0 ) return;
sqlite3ExprCode(pParse, p->pLimit);
sqlite3VdbeAddOp(v, OP_MustBeInt, 0, 0);
sqlite3VdbeAddOp(v, OP_Negative, 0, 0);
sqlite3VdbeAddOp(v, OP_MemStore, iMem, 1);
sqlite3VdbeAddOp(v, OP_MemStore, iMem, 0);
VdbeComment((v, "# LIMIT counter"));
sqlite3VdbeAddOp(v, OP_IfMemZero, iMem, iBreak);
p->iLimit = iMem;
@@ -1393,10 +1410,18 @@ static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
sqlite3ExprCode(pParse, p->pOffset);
sqlite3VdbeAddOp(v, OP_MustBeInt, 0, 0);
sqlite3VdbeAddOp(v, OP_Negative, 0, 0);
sqlite3VdbeAddOp(v, OP_MemStore, iMem, 1);
sqlite3VdbeAddOp(v, OP_MemStore, iMem, p->pLimit==0);
VdbeComment((v, "# OFFSET counter"));
if( p->pLimit ){
sqlite3VdbeAddOp(v, OP_Add, 0, 0);
}
p->iOffset = iMem;
}
if( p->pLimit ){
Vdbe *v = pParse->pVdbe;
sqlite3VdbeAddOp(v, OP_MemStore, p->iLimit+1, 1);
VdbeComment((v, "# LIMIT+OFFSET"));
}
}
/*