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Commitdcc685d

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Fix pull_up_sublinks' failure to handle nested pull-up opportunities.
After finding an EXISTS or ANY sub-select that can be converted to asemi-join or anti-join, we should recurse into the body of the sub-select.This allows cases such as EXISTS-within-EXISTS to be optimized properly.The original coding would leave the lower sub-select as a SubLink, whichis no better and often worse than what we can do with a join. Per examplefrom Wayne Conrad.Back-patch to 8.4. There is a related issue in older versions' handlingof pull_up_IN_clauses, but they're lame enough anyway about the whole areathat it seems not worth the extra work to try to fix.
1 parent52897e5 commitdcc685d

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2 files changed

+43
-3
lines changed

2 files changed

+43
-3
lines changed

‎src/backend/optimizer/plan/subselect.c‎

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1065,6 +1065,11 @@ SS_process_ctes(PlannerInfo *root)
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* (Notionally, we replace the SubLink with a constant TRUE, then elide the
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* redundant constant from the qual.)
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*
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* On success, the caller is also responsible for recursively applying
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* pull_up_sublinks processing to the rarg and quals of the returned JoinExpr.
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* (On failure, there is no need to do anything, since pull_up_sublinks will
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* be applied when we recursively plan the sub-select.)
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*
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* Side effects of a successful conversion include adding the SubLink's
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* subselect to the query's rangetable, so that it can be referenced in
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* the JoinExpr's rarg.

‎src/backend/optimizer/prep/prepjointree.c‎

Lines changed: 38 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -318,6 +318,7 @@ pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
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{
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SubLink*sublink= (SubLink*)node;
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JoinExpr*j;
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Relidschild_rels;
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/* Is it a convertible ANY or EXISTS clause? */
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if (sublink->subLinkType==ANY_SUBLINK)
@@ -326,7 +327,18 @@ pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
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available_rels);
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if (j)
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{
329-
/* Yes, insert the new join node into the join tree */
330+
/* Yes; recursively process what we pulled up */
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j->rarg=pull_up_sublinks_jointree_recurse(root,
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j->rarg,
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&child_rels);
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/* Pulled-up ANY/EXISTS quals can use those rels too */
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child_rels=bms_add_members(child_rels,available_rels);
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/* ... and any inserted joins get stacked onto j->rarg */
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j->quals=pull_up_sublinks_qual_recurse(root,
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j->quals,
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child_rels,
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&j->rarg);
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/* Now insert the new join node into the join tree */
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j->larg=*jtlink;
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*jtlink= (Node*)j;
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/* and return NULL representing constant TRUE */
@@ -339,7 +351,18 @@ pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
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available_rels);
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if (j)
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{
342-
/* Yes, insert the new join node into the join tree */
354+
/* Yes; recursively process what we pulled up */
355+
j->rarg=pull_up_sublinks_jointree_recurse(root,
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j->rarg,
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&child_rels);
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/* Pulled-up ANY/EXISTS quals can use those rels too */
359+
child_rels=bms_add_members(child_rels,available_rels);
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/* ... and any inserted joins get stacked onto j->rarg */
361+
j->quals=pull_up_sublinks_qual_recurse(root,
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j->quals,
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child_rels,
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&j->rarg);
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/* Now insert the new join node into the join tree */
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j->larg=*jtlink;
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*jtlink= (Node*)j;
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/* and return NULL representing constant TRUE */
@@ -354,6 +377,7 @@ pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
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/* If the immediate argument of NOT is EXISTS, try to convert */
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SubLink*sublink= (SubLink*)get_notclausearg((Expr*)node);
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JoinExpr*j;
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Relidschild_rels;
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if (sublink&&IsA(sublink,SubLink))
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{
@@ -363,7 +387,18 @@ pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
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available_rels);
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if (j)
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{
366-
/* Yes, insert the new join node into the join tree */
390+
/* Yes; recursively process what we pulled up */
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j->rarg=pull_up_sublinks_jointree_recurse(root,
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j->rarg,
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&child_rels);
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/* Pulled-up ANY/EXISTS quals can use those rels too */
395+
child_rels=bms_add_members(child_rels,available_rels);
396+
/* ... and any inserted joins get stacked onto j->rarg */
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j->quals=pull_up_sublinks_qual_recurse(root,
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j->quals,
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child_rels,
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&j->rarg);
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/* Now insert the new join node into the join tree */
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j->larg=*jtlink;
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*jtlink= (Node*)j;
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/* and return NULL representing constant TRUE */

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