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Overview
| Comment: | An experimental optimization to DISTINCT that causes an immediate exit of the inner loop of a join following each output row if the inner loop does not contribute any columns to the result set. |
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| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | distinct-early-out |
| Files: | files | file ages | folders |
| SHA3-256: |
a33f88acd7e02361fac1874c71dae1db |
| User & Date: | drh 2017-11-21 23:47:42.367 |
Context
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2017-11-21
| ||
| 23:47 | An experimental optimization to DISTINCT that causes an immediate exit of the inner loop of a join following each output row if the inner loop does not contribute any columns to the result set. (Leaf check-in: a33f88acd7 user: drh tags: distinct-early-out) | |
| 23:38 | Fix the skip-ahead-distinct optimization on joins for cases there the table in the inner loop of the join does not contribute any columns to the result set. Proposed fix for ticket [ef9318757b152e3a2] (check-in: 2dcef5a9ae user: drh tags: trunk) | |
Changes
Changes to src/where.c.
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Parse *pParse = pWInfo->pParse;
Vdbe *v = pParse->pVdbe;
int i;
WhereLevel *pLevel;
WhereLoop *pLoop;
SrcList *pTabList = pWInfo->pTabList;
sqlite3 *db = pParse->db;
/* Generate loop termination code.
*/
VdbeModuleComment((v, "End WHERE-core"));
sqlite3ExprCacheClear(pParse);
for(i=pWInfo->nLevel-1; i>=0; i--){
int addr;
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Parse *pParse = pWInfo->pParse;
Vdbe *v = pParse->pVdbe;
int i;
WhereLevel *pLevel;
WhereLoop *pLoop;
SrcList *pTabList = pWInfo->pTabList;
sqlite3 *db = pParse->db;
/* For a DISTINCT join in which no columns of inner loops appear in
** the result set, put a jump right after the inner loop body that
** causes the unused inner loops to exit.
*/
if( pWInfo->eDistinct==WHERE_DISTINCT_ORDERED
&& pWInfo->nLevel>1
){
Bitmask tabUsed;
tabUsed = sqlite3WhereExprListUsage(&pWInfo->sMaskSet, pWInfo->pResultSet);
for(i=pWInfo->nLevel-1; i>=0; i--){
pLoop = pWInfo->a[i].pWLoop;
if( (tabUsed & pLoop->maskSelf)!=0 ) break;
}
if( i<pWInfo->nLevel-1 ){
sqlite3VdbeGoto(v, pWInfo->a[i].addrCont);
}
}
/* Generate loop termination code.
*/
VdbeModuleComment((v, "End WHERE-core"));
sqlite3ExprCacheClear(pParse);
for(i=pWInfo->nLevel-1; i>=0; i--){
int addr;
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