From: Tom Lane Date: Mon, 22 Jun 2015 22:53:27 +0000 (-0400) Subject: Improve inheritance_planner()'s performance for large inheritance sets. X-Git-Tag: REL9_5_ALPHA1~40 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=2cb9ec1bcb35dd6b4cf7a4a325aaa9791444e69d;p=postgresql Improve inheritance_planner()'s performance for large inheritance sets. Commit c03ad5602f529787968fa3201b35c119bbc6d782 introduced a planner performance regression for UPDATE/DELETE on large inheritance sets. It required copying the append_rel_list (which is of size proportional to the number of inherited tables) once for each inherited table, thus resulting in O(N^2) time and memory consumption. While it's difficult to avoid that in general, the extra work only has to be done for append_rel_list entries that actually reference subquery RTEs, which inheritance-set entries will not. So we can buy back essentially all of the loss in cases without subqueries in FROM; and even for those, the added work is mainly proportional to the number of UNION ALL subqueries. Back-patch to 9.2, like the previous commit. Tom Lane and Dean Rasheed, per a complaint from Thomas Munro. --- diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c index 8afde2b7d5..a6ce96efc4 100644 --- a/src/backend/optimizer/plan/planner.c +++ b/src/backend/optimizer/plan/planner.c @@ -834,7 +834,9 @@ inheritance_planner(PlannerInfo *root) { Query *parse = root->parse; int parentRTindex = parse->resultRelation; - Bitmapset *resultRTindexes = NULL; + Bitmapset *resultRTindexes; + Bitmapset *subqueryRTindexes; + Bitmapset *modifiableARIindexes; int nominalRelation = -1; List *final_rtable = NIL; int save_rel_array_size = 0; @@ -845,6 +847,7 @@ inheritance_planner(PlannerInfo *root) List *returningLists = NIL; List *rowMarks; ListCell *lc; + Index rti; Assert(parse->commandType != CMD_INSERT); @@ -867,8 +870,10 @@ inheritance_planner(PlannerInfo *root) * subqueries during planning, and so we must create copies of them too, * except where they are target relations, which will each only be used in * a single plan. + * + * To begin with, we'll need a bitmapset of the target relation relids. */ - resultRTindexes = bms_add_member(resultRTindexes, parentRTindex); + resultRTindexes = bms_make_singleton(parentRTindex); foreach(lc, root->append_rel_list) { AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc); @@ -878,12 +883,57 @@ inheritance_planner(PlannerInfo *root) appinfo->child_relid); } + /* + * Now, generate a bitmapset of the relids of the subquery RTEs, including + * security-barrier RTEs that will become subqueries, as just explained. + */ + subqueryRTindexes = NULL; + rti = 1; + foreach(lc, parse->rtable) + { + RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc); + + if (rte->rtekind == RTE_SUBQUERY || + (rte->securityQuals != NIL && + !bms_is_member(rti, resultRTindexes))) + subqueryRTindexes = bms_add_member(subqueryRTindexes, rti); + rti++; + } + + /* + * Next, we want to identify which AppendRelInfo items contain references + * to any of the aforesaid subquery RTEs. These items will need to be + * copied and modified to adjust their subquery references; whereas the + * other ones need not be touched. It's worth being tense over this + * because we can usually avoid processing most of the AppendRelInfo + * items, thereby saving O(N^2) space and time when the target is a large + * inheritance tree. We can identify AppendRelInfo items by their + * child_relid, since that should be unique within the list. + */ + modifiableARIindexes = NULL; + if (subqueryRTindexes != NULL) + { + foreach(lc, root->append_rel_list) + { + AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc); + + if (bms_is_member(appinfo->parent_relid, subqueryRTindexes) || + bms_is_member(appinfo->child_relid, subqueryRTindexes) || + bms_overlap(pull_varnos((Node *) appinfo->translated_vars), + subqueryRTindexes)) + modifiableARIindexes = bms_add_member(modifiableARIindexes, + appinfo->child_relid); + } + } + + /* + * And now we can get on with generating a plan for each child table. + */ foreach(lc, root->append_rel_list) { AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc); PlannerInfo subroot; Plan *subplan; - Index rti; /* append_rel_list contains all append rels; ignore others */ if (appinfo->parent_relid != parentRTindex) @@ -917,9 +967,29 @@ inheritance_planner(PlannerInfo *root) /* * The append_rel_list likewise might contain references to subquery * RTEs (if any subqueries were flattenable UNION ALLs). So prepare - * to apply ChangeVarNodes to that, too. + * to apply ChangeVarNodes to that, too. As explained above, we only + * want to copy items that actually contain such references; the rest + * can just get linked into the subroot's append_rel_list. + * + * If we know there are no such references, we can just use the outer + * append_rel_list unmodified. */ - subroot.append_rel_list = (List *) copyObject(root->append_rel_list); + if (modifiableARIindexes != NULL) + { + ListCell *lc2; + + subroot.append_rel_list = NIL; + foreach(lc2, root->append_rel_list) + { + AppendRelInfo *appinfo2 = (AppendRelInfo *) lfirst(lc2); + + if (bms_is_member(appinfo2->child_relid, modifiableARIindexes)) + appinfo2 = (AppendRelInfo *) copyObject(appinfo2); + + subroot.append_rel_list = lappend(subroot.append_rel_list, + appinfo2); + } + } /* * Add placeholders to the child Query's rangetable list to fill the @@ -933,13 +1003,13 @@ inheritance_planner(PlannerInfo *root) /* * If this isn't the first child Query, generate duplicates of all - * subquery RTEs, and adjust Var numbering to reference the - * duplicates. To simplify the loop logic, we scan the original rtable - * not the copy just made by adjust_appendrel_attrs; that should be OK - * since subquery RTEs couldn't contain any references to the target - * rel. + * subquery (or subquery-to-be) RTEs, and adjust Var numbering to + * reference the duplicates. To simplify the loop logic, we scan the + * original rtable not the copy just made by adjust_appendrel_attrs; + * that should be OK since subquery RTEs couldn't contain any + * references to the target rel. */ - if (final_rtable != NIL) + if (final_rtable != NIL && subqueryRTindexes != NULL) { ListCell *lr; @@ -948,14 +1018,7 @@ inheritance_planner(PlannerInfo *root) { RangeTblEntry *rte = (RangeTblEntry *) lfirst(lr); - /* - * Copy subquery RTEs and RTEs with security barrier quals - * that will be turned into subqueries, except those that are - * target relations. - */ - if (rte->rtekind == RTE_SUBQUERY || - (rte->securityQuals != NIL && - !bms_is_member(rti, resultRTindexes))) + if (bms_is_member(rti, subqueryRTindexes)) { Index newrti; @@ -968,7 +1031,20 @@ inheritance_planner(PlannerInfo *root) newrti = list_length(subroot.parse->rtable) + 1; ChangeVarNodes((Node *) subroot.parse, rti, newrti, 0); ChangeVarNodes((Node *) subroot.rowMarks, rti, newrti, 0); - ChangeVarNodes((Node *) subroot.append_rel_list, rti, newrti, 0); + /* Skip processing unchanging parts of append_rel_list */ + if (modifiableARIindexes != NULL) + { + ListCell *lc2; + + foreach(lc2, subroot.append_rel_list) + { + AppendRelInfo *appinfo2 = (AppendRelInfo *) lfirst(lc2); + + if (bms_is_member(appinfo2->child_relid, + modifiableARIindexes)) + ChangeVarNodes((Node *) appinfo2, rti, newrti, 0); + } + } rte = copyObject(rte); ChangeVarNodes((Node *) rte->securityQuals, rti, newrti, 0); subroot.parse->rtable = lappend(subroot.parse->rtable,