From: Robert Haas Date: Mon, 20 Oct 2025 18:23:42 +0000 (-0400) Subject: Store information about elided nodes in the final plan. X-Git-Url: http://git.postgresql.org/gitweb/static/close/reject?a=commitdiff_plain;h=94f6396adb94363b5c4bdfc0aea38e5593f82d36;p=users%2Frhaas%2Fpostgres.git Store information about elided nodes in the final plan. An extension (or core code) might want to reconstruct the planner's choice of join order from the final plan. To do so, it must be possible to find all of the RTIs that were part of the join problem in that plan. The previous commit, together with the earlier work in 8c49a484e8ebb0199fba4bd68eaaedaf49b48ed0, is enough to let us match up RTIs we see in the final plan with RTIs that we see during the planning cycle, but we still have a problem if the planner decides to drop some RTIs out of the final plan altogether. To fix that, when setrefs.c removes a SubqueryScan, single-child Append, or single-child MergeAppend from the final Plan tree, record the type of the removed node and the RTIs that the removed node would have scanned in the final plan tree. It would be natural to record this information on the child of the removed plan node, but that would require adding an additional pointer field to type Plan, which seems undesirable. So, instead, store the information in a separate list that the executor need never consult, and use the plan_node_id to identify the plan node with which the removed node is logically associated. Also, update pg_overexplain to display these details. --- diff --git a/contrib/pg_overexplain/expected/pg_overexplain.out b/contrib/pg_overexplain/expected/pg_overexplain.out index 55d34666d8..ca9a23ea61 100644 --- a/contrib/pg_overexplain/expected/pg_overexplain.out +++ b/contrib/pg_overexplain/expected/pg_overexplain.out @@ -452,6 +452,8 @@ SELECT * FROM vegetables WHERE genus = 'daucus'; Seq Scan on daucus vegetables Filter: (genus = 'daucus'::text) Scan RTI: 2 + Elided Node Type: Append + Elided Node RTIs: 1 RTI 1 (relation, inherited, in-from-clause): Eref: vegetables (id, name, genus) Relation: vegetables @@ -465,7 +467,7 @@ SELECT * FROM vegetables WHERE genus = 'daucus'; Relation Kind: relation Relation Lock Mode: AccessShareLock Unprunable RTIs: 1 2 -(16 rows) +(18 rows) -- Also test a case that involves a write. EXPLAIN (RANGE_TABLE, COSTS OFF) diff --git a/contrib/pg_overexplain/pg_overexplain.c b/contrib/pg_overexplain/pg_overexplain.c index 5dc707d69e..fa907fa472 100644 --- a/contrib/pg_overexplain/pg_overexplain.c +++ b/contrib/pg_overexplain/pg_overexplain.c @@ -191,6 +191,8 @@ overexplain_per_node_hook(PlanState *planstate, List *ancestors, */ if (options->range_table) { + bool opened_elided_nodes = false; + switch (nodeTag(plan)) { case T_SeqScan: @@ -251,6 +253,43 @@ overexplain_per_node_hook(PlanState *planstate, List *ancestors, default: break; } + + foreach_node(ElidedNode, n, es->pstmt->elidedNodes) + { + char *elidednodetag; + + if (n->plan_node_id != plan->plan_node_id) + continue; + + if (!opened_elided_nodes) + { + ExplainOpenGroup("Elided Nodes", "Elided Nodes", false, es); + opened_elided_nodes = true; + } + + switch (n->elided_type) + { + case T_Append: + elidednodetag = "Append"; + break; + case T_MergeAppend: + elidednodetag = "MergeAppend"; + break; + case T_SubqueryScan: + elidednodetag = "SubqueryScan"; + break; + default: + elidednodetag = psprintf("%d", n->elided_type); + break; + } + + ExplainOpenGroup("Elided Node", NULL, true, es); + ExplainPropertyText("Elided Node Type", elidednodetag, es); + overexplain_bitmapset("Elided Node RTIs", n->relids, es); + ExplainCloseGroup("Elided Node", NULL, true, es); + } + if (opened_elided_nodes) + ExplainCloseGroup("Elided Nodes", "Elided Nodes", false, es); } } diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c index 0e6b3f60f3..9d5262651e 100644 --- a/src/backend/optimizer/plan/planner.c +++ b/src/backend/optimizer/plan/planner.c @@ -618,6 +618,7 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions, result->paramExecTypes = glob->paramExecTypes; /* utilityStmt should be null, but we might as well copy it */ result->utilityStmt = parse->utilityStmt; + result->elidedNodes = glob->elidedNodes; result->stmt_location = parse->stmt_location; result->stmt_len = parse->stmt_len; diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c index adabae09a2..23a00d452b 100644 --- a/src/backend/optimizer/plan/setrefs.c +++ b/src/backend/optimizer/plan/setrefs.c @@ -211,6 +211,9 @@ static List *set_windowagg_runcondition_references(PlannerInfo *root, List *runcondition, Plan *plan); +static void record_elided_node(PlannerGlobal *glob, int plan_node_id, + NodeTag elided_type, Bitmapset *relids); + /***************************************************************************** * @@ -1460,10 +1463,17 @@ set_subqueryscan_references(PlannerInfo *root, if (trivial_subqueryscan(plan)) { + Index scanrelid; + /* * We can omit the SubqueryScan node and just pull up the subplan. */ result = clean_up_removed_plan_level((Plan *) plan, plan->subplan); + + /* Remember that we removed a SubqueryScan */ + scanrelid = plan->scan.scanrelid + rtoffset; + record_elided_node(root->glob, plan->subplan->plan_node_id, + T_SubqueryScan, bms_make_singleton(scanrelid)); } else { @@ -1891,7 +1901,17 @@ set_append_references(PlannerInfo *root, Plan *p = (Plan *) linitial(aplan->appendplans); if (p->parallel_aware == aplan->plan.parallel_aware) - return clean_up_removed_plan_level((Plan *) aplan, p); + { + Plan *result; + + result = clean_up_removed_plan_level((Plan *) aplan, p); + + /* Remember that we removed an Append */ + record_elided_node(root->glob, p->plan_node_id, T_Append, + offset_relid_set(aplan->apprelids, rtoffset)); + + return result; + } } /* @@ -1959,7 +1979,17 @@ set_mergeappend_references(PlannerInfo *root, Plan *p = (Plan *) linitial(mplan->mergeplans); if (p->parallel_aware == mplan->plan.parallel_aware) - return clean_up_removed_plan_level((Plan *) mplan, p); + { + Plan *result; + + result = clean_up_removed_plan_level((Plan *) mplan, p); + + /* Remember that we removed a MergeAppend */ + record_elided_node(root->glob, p->plan_node_id, T_MergeAppend, + offset_relid_set(mplan->apprelids, rtoffset)); + + return result; + } } /* @@ -3774,3 +3804,21 @@ extract_query_dependencies_walker(Node *node, PlannerInfo *context) return expression_tree_walker(node, extract_query_dependencies_walker, context); } + +/* + * Record some details about a node removed from the plan during setrefs + * procesing, for the benefit of code trying to reconstruct planner decisions + * from examination of the final plan tree. + */ +static void +record_elided_node(PlannerGlobal *glob, int plan_node_id, + NodeTag elided_type, Bitmapset *relids) +{ + ElidedNode *n = makeNode(ElidedNode); + + n->plan_node_id = plan_node_id; + n->elided_type = elided_type; + n->relids = relids; + + glob->elidedNodes = lappend(glob->elidedNodes, n); +} diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h index a3a800869d..cf3a16b8b0 100644 --- a/src/include/nodes/pathnodes.h +++ b/src/include/nodes/pathnodes.h @@ -159,6 +159,9 @@ typedef struct PlannerGlobal /* type OIDs for PARAM_EXEC Params */ List *paramExecTypes; + /* info about nodes elided from the plan during setrefs processing */ + List *elidedNodes; + /* highest PlaceHolderVar ID assigned */ Index lastPHId; diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h index 1526dd2ec6..5d0520d5e5 100644 --- a/src/include/nodes/plannodes.h +++ b/src/include/nodes/plannodes.h @@ -152,6 +152,9 @@ typedef struct PlannedStmt /* non-null if this is utility stmt */ Node *utilityStmt; + /* info about nodes elided from the plan during setrefs processing */ + List *elidedNodes; + /* * DefElem objects added by extensions, e.g. using planner_shutdown_hook * @@ -1838,4 +1841,18 @@ typedef struct SubPlanRTInfo bool dummy; } SubPlanRTInfo; +/* + * ElidedNode + * + * Information about nodes elided from the final plan tree: trivial subquery + * scans, and single-child Append and MergeAppend nodes. + */ +typedef struct ElidedNode +{ + NodeTag type; + int plan_node_id; + NodeTag elided_type; + Bitmapset *relids; +} ElidedNode; + #endif /* PLANNODES_H */ diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 60aa0b0937..4ff47115ca 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -698,6 +698,7 @@ EachState Edge EditableObjectType ElementsState +ElidedNode EnableTimeoutParams EndDataPtrType EndDirectModify_function