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Overview
| Comment: | Put a limit counter on the query planner that restricts the number of index+constraint options that can be considered for each table in a join. This prevents certain pathological queries from taking up too much time in the query planner. |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA3-256: |
8690b5a0cc08eeb175230de45d4ca9b9 |
| User & Date: | drh 2018-09-21 18:43:51 |
Context
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2018-09-21
| ||
| 19:06 | Comment typo fixed. No code changes. (check-in: 7e68cdab user: drh tags: trunk) | |
| 18:43 | Put a limit counter on the query planner that restricts the number of index+constraint options that can be considered for each table in a join. This prevents certain pathological queries from taking up too much time in the query planner. (check-in: 8690b5a0 user: drh tags: trunk) | |
| 13:07 | Optimization to the OP_MakeRecord opcode makes speed-check.sh run about 1.1 million cycles faster, and results in a slightly smaller library. (check-in: d10e6362 user: drh tags: trunk) | |
Changes
Changes to src/where.c.
2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 .... 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 .... 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 |
** (4) The template has the same or lower cost than the current loop
*/
static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
WhereLoop **ppPrev, *p;
WhereInfo *pWInfo = pBuilder->pWInfo;
sqlite3 *db = pWInfo->pParse->db;
int rc;
/* If pBuilder->pOrSet is defined, then only keep track of the costs
** and prereqs.
*/
if( pBuilder->pOrSet!=0 ){
if( pTemplate->nLTerm ){
#if WHERETRACE_ENABLED
................................................................................
int rc = SQLITE_OK;
WhereLoop *pNew;
u8 priorJointype = 0;
/* Loop over the tables in the join, from left to right */
pNew = pBuilder->pNew;
whereLoopInit(pNew);
for(iTab=0, pItem=pTabList->a; pItem<pEnd; iTab++, pItem++){
Bitmask mUnusable = 0;
pNew->iTab = iTab;
pNew->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, pItem->iCursor);
if( ((pItem->fg.jointype|priorJointype) & (JT_LEFT|JT_CROSS))!=0 ){
/* This condition is true when pItem is the FROM clause term on the
** right-hand-side of a LEFT or CROSS JOIN. */
mPrereq = mPrior;
}
priorJointype = pItem->fg.jointype;
................................................................................
{
rc = whereLoopAddBtree(pBuilder, mPrereq);
}
if( rc==SQLITE_OK && pBuilder->pWC->hasOr ){
rc = whereLoopAddOr(pBuilder, mPrereq, mUnusable);
}
mPrior |= pNew->maskSelf;
if( rc || db->mallocFailed ) break;
}
whereLoopClear(db, pNew);
return rc;
}
/*
|
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2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 .... 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 .... 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 |
** (4) The template has the same or lower cost than the current loop
*/
static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
WhereLoop **ppPrev, *p;
WhereInfo *pWInfo = pBuilder->pWInfo;
sqlite3 *db = pWInfo->pParse->db;
int rc;
/* Stop the search once we hit the query planner search limit */
if( pBuilder->iPlanLimit==0 ) return SQLITE_DONE;
pBuilder->iPlanLimit--;
/* If pBuilder->pOrSet is defined, then only keep track of the costs
** and prereqs.
*/
if( pBuilder->pOrSet!=0 ){
if( pTemplate->nLTerm ){
#if WHERETRACE_ENABLED
................................................................................
int rc = SQLITE_OK;
WhereLoop *pNew;
u8 priorJointype = 0;
/* Loop over the tables in the join, from left to right */
pNew = pBuilder->pNew;
whereLoopInit(pNew);
/* Some pathological queries provide an unreasonable number of indexing
** options. The iPlanLimit value prevents these queries from taking up
** too much time in the planner. When iPlanLimit reaches zero, no further
** index+constraint options are considered. Seed iPlanLimit to 10K but
** also add an extra 1K to each table of the join, to ensure that each
** table at least gets 1K opportunities. */
pBuilder->iPlanLimit = 10000;
for(iTab=0, pItem=pTabList->a; pItem<pEnd; iTab++, pItem++){
Bitmask mUnusable = 0;
pNew->iTab = iTab;
pBuilder->iPlanLimit += 1000; /* 1000 bonus for each table in the join */
pNew->maskSelf = sqlite3WhereGetMask(&pWInfo->sMaskSet, pItem->iCursor);
if( ((pItem->fg.jointype|priorJointype) & (JT_LEFT|JT_CROSS))!=0 ){
/* This condition is true when pItem is the FROM clause term on the
** right-hand-side of a LEFT or CROSS JOIN. */
mPrereq = mPrior;
}
priorJointype = pItem->fg.jointype;
................................................................................
{
rc = whereLoopAddBtree(pBuilder, mPrereq);
}
if( rc==SQLITE_OK && pBuilder->pWC->hasOr ){
rc = whereLoopAddOr(pBuilder, mPrereq, mUnusable);
}
mPrior |= pNew->maskSelf;
if( rc || db->mallocFailed ){
if( rc==SQLITE_DONE ){
/* We hit the query planner search limit set by iPlanLimit */
rc = SQLITE_OK;
}else{
break;
}
}
}
whereLoopClear(db, pNew);
return rc;
}
/*
|
Changes to src/whereInt.h.
398 399 400 401 402 403 404 405 406 407 408 409 410 411 |
WhereLoop *pNew; /* Template WhereLoop */ WhereOrSet *pOrSet; /* Record best loops here, if not NULL */ #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 UnpackedRecord *pRec; /* Probe for stat4 (if required) */ int nRecValid; /* Number of valid fields currently in pRec */ #endif unsigned int bldFlags; /* SQLITE_BLDF_* flags */ }; /* Allowed values for WhereLoopBuider.bldFlags */ #define SQLITE_BLDF_INDEXED 0x0001 /* An index is used */ #define SQLITE_BLDF_UNIQUE 0x0002 /* All keys of a UNIQUE index used */ /* |
> |
398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 |
WhereLoop *pNew; /* Template WhereLoop */
WhereOrSet *pOrSet; /* Record best loops here, if not NULL */
#ifdef SQLITE_ENABLE_STAT3_OR_STAT4
UnpackedRecord *pRec; /* Probe for stat4 (if required) */
int nRecValid; /* Number of valid fields currently in pRec */
#endif
unsigned int bldFlags; /* SQLITE_BLDF_* flags */
unsigned int iPlanLimit; /* Search limiter */
};
/* Allowed values for WhereLoopBuider.bldFlags */
#define SQLITE_BLDF_INDEXED 0x0001 /* An index is used */
#define SQLITE_BLDF_UNIQUE 0x0002 /* All keys of a UNIQUE index used */
/*
|