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Overview
| Comment: | Adjustments to the implementation of LIMIT so that it uses fewer opcodes. |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
39d5b292d27faf00ab58ff4074f91f7a |
| User & Date: | drh 2009-11-12 03:13:26.000 |
Context
|
2009-11-12
| ||
| 03:46 | Suppress excess OP_Null opcodes caused by binary IS or IS NOT operators that are converted into unary ISNULL or NOTNULL operators. (check-in: cff1b36ab2 user: drh tags: trunk) | |
| 03:13 | Adjustments to the implementation of LIMIT so that it uses fewer opcodes. (check-in: 39d5b292d2 user: drh tags: trunk) | |
|
2009-11-11
| ||
| 23:58 | If the sector size is unspecified (initially 0) then set it to 512, not to 32. (check-in: 8861b5c160 user: drh tags: trunk) | |
Changes
Changes to src/select.c.
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}
/* Jump to the end of the loop if the LIMIT is reached.
*/
if( p->iLimit ){
assert( pOrderBy==0 ); /* If there is an ORDER BY, the call to
** pushOntoSorter() would have cleared p->iLimit */
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}
/* Jump to the end of the loop if the LIMIT is reached.
*/
if( p->iLimit ){
assert( pOrderBy==0 ); /* If there is an ORDER BY, the call to
** pushOntoSorter() would have cleared p->iLimit */
sqlite3VdbeAddOp3(v, OP_IfZero, p->iLimit, iBreak, -1);
}
}
/*
** Given an expression list, generate a KeyInfo structure that records
** the collating sequence for each expression in that expression list.
**
|
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** the reuse of the same limit and offset registers across multiple
** SELECT statements.
*/
static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
Vdbe *v = 0;
int iLimit = 0;
int iOffset;
| | > > > > > > > > | | | | > | 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 |
** the reuse of the same limit and offset registers across multiple
** SELECT statements.
*/
static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
Vdbe *v = 0;
int iLimit = 0;
int iOffset;
int addr1, n;
if( p->iLimit ) return;
/*
** "LIMIT -1" always shows all rows. There is some
** contraversy about what the correct behavior should be.
** The current implementation interprets "LIMIT 0" to mean
** no rows.
*/
sqlite3ExprCacheClear(pParse);
assert( p->pOffset==0 || p->pLimit!=0 );
if( p->pLimit ){
p->iLimit = iLimit = ++pParse->nMem;
v = sqlite3GetVdbe(pParse);
if( NEVER(v==0) ) return; /* VDBE should have already been allocated */
if( sqlite3ExprIsInteger(p->pLimit, &n) ){
if( n==0 ){
sqlite3VdbeAddOp2(v, OP_Goto, 0, iBreak);
}else{
sqlite3VdbeAddOp2(v, OP_Integer, n, iLimit);
VdbeComment((v, "LIMIT counter"));
}
}else{
sqlite3ExprCode(pParse, p->pLimit, iLimit);
sqlite3VdbeAddOp1(v, OP_MustBeInt, iLimit);
VdbeComment((v, "LIMIT counter"));
sqlite3VdbeAddOp2(v, OP_IfZero, iLimit, iBreak);
}
if( p->pOffset ){
p->iOffset = iOffset = ++pParse->nMem;
pParse->nMem++; /* Allocate an extra register for limit+offset */
sqlite3ExprCode(pParse, p->pOffset, iOffset);
sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset);
VdbeComment((v, "OFFSET counter"));
addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iOffset);
|
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break;
}
}
/* Jump to the end of the loop if the LIMIT is reached.
*/
if( p->iLimit ){
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break;
}
}
/* Jump to the end of the loop if the LIMIT is reached.
*/
if( p->iLimit ){
sqlite3VdbeAddOp3(v, OP_IfZero, p->iLimit, iBreak, -1);
}
/* Generate the subroutine return
*/
sqlite3VdbeResolveLabel(v, iContinue);
sqlite3VdbeAddOp1(v, OP_Return, regReturn);
|
| ︙ | ︙ |
Changes to src/vdbe.c.
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assert( pIn1->flags&MEM_Int );
if( pIn1->u.i<0 ){
pc = pOp->p2 - 1;
}
break;
}
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assert( pIn1->flags&MEM_Int );
if( pIn1->u.i<0 ){
pc = pOp->p2 - 1;
}
break;
}
/* Opcode: IfZero P1 P2 P3 * *
**
** The register P1 must contain an integer. Add literal P3 to the
** value in register P1. If the result is exactly 0, jump to P2.
**
** It is illegal to use this instruction on a register that does
** not contain an integer. An assertion fault will result if you try.
*/
case OP_IfZero: { /* jump, in1 */
assert( pIn1->flags&MEM_Int );
pIn1->u.i += pOp->p3;
if( pIn1->u.i==0 ){
pc = pOp->p2 - 1;
}
break;
}
/* Opcode: AggStep * P2 P3 P4 P5
|
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