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Overview
| Comment: | Avoid adding an artifical "LIMIT 1" on scalar subqueries that do not need it. This seems like a pointless optimization as it makes minimal run-time difference but does increase code complexity. Parked on a branch for historical reference. |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | subquery-limit-opt |
| Files: | files | file ages | folders |
| SHA3-256: |
c21628e9c166d8481138e04cfbc2ea5a |
| User & Date: | drh 2017-06-17 19:06:17 |
Context
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2017-06-17
| ||
| 19:06 | Avoid adding an artifical "LIMIT 1" on scalar subqueries that do not need it. This seems like a pointless optimization as it makes minimal run-time difference but does increase code complexity. Parked on a branch for historical reference. Leaf check-in: c21628e9 user: drh tags: subquery-limit-opt | |
| 18:49 | Fix a missing comma in the previous check-in. check-in: f3db02f4 user: drh tags: trunk | |
Changes
Changes to src/expr.c.
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VdbeComment((v, "Init subquery result"));
}else{
dest.eDest = SRT_Exists;
sqlite3VdbeAddOp2(v, OP_Integer, 0, dest.iSDParm);
VdbeComment((v, "Init EXISTS result"));
}
sqlite3ExprDelete(pParse->db, pSel->pLimit);
pSel->pLimit = sqlite3ExprAlloc(pParse->db, TK_INTEGER,
&sqlite3IntTokens[1], 0);
pSel->iLimit = 0;
pSel->selFlags &= ~SF_MultiValue;
if( sqlite3Select(pParse, pSel, &dest) ){
return 0;
}
rReg = dest.iSDParm;
ExprSetVVAProperty(pExpr, EP_NoReduce);
|
> > > | | > |
2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 |
VdbeComment((v, "Init subquery result"));
}else{
dest.eDest = SRT_Exists;
sqlite3VdbeAddOp2(v, OP_Integer, 0, dest.iSDParm);
VdbeComment((v, "Init EXISTS result"));
}
sqlite3ExprDelete(pParse->db, pSel->pLimit);
if( (pSel->selFlags & SF_Aggregate)!=0 && pSel->pGroupBy==0 ){
pSel->pLimit = 0;
}else{
pSel->pLimit = sqlite3ExprAlloc(pParse->db, TK_INTEGER,
&sqlite3IntTokens[1], 0);
}
pSel->iLimit = 0;
pSel->selFlags &= ~SF_MultiValue;
if( sqlite3Select(pParse, pSel, &dest) ){
return 0;
}
rReg = dest.iSDParm;
ExprSetVVAProperty(pExpr, EP_NoReduce);
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