v1-0001-Add-a-list-of-all-PlannerInfo-roots-to-PlannerGlo.patch

From 31f4e33142227bd31355aa2042ae0823937a36bd Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Mon, 8 Dec 2025 13:46:43 -0500
Subject: [PATCH v1 1/2] Add a list of all PlannerInfo "roots" to
 PlannerGlobal.

This can serve the same purpose as glob->subplanNames, namely, to make
sure that we don't assign the same name to more than one subplan, but it
also can be used to locate a given subplan name, which is something that
glob->subplanNames cannot do.

This commit does not remove glob->subplanNames, but it ensures that
glob->allroots and glob->subplanNames have equivalent contents at the
key point in the code, namely, the start of choose_plan_name.
---
 src/backend/optimizer/plan/planagg.c      |  1 +
 src/backend/optimizer/plan/planner.c      | 50 +++++++++++++++++++++--
 src/backend/optimizer/prep/prepjointree.c |  7 ++++
 src/include/nodes/pathnodes.h             |  3 ++
 src/include/optimizer/planner.h           |  1 +
 5 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/src/backend/optimizer/plan/planagg.c b/src/backend/optimizer/plan/planagg.c
index a2ac58d246e..f138f372e7d 100644
--- a/src/backend/optimizer/plan/planagg.c
+++ b/src/backend/optimizer/plan/planagg.c
@@ -341,6 +341,7 @@ build_minmax_path(PlannerInfo *root, MinMaxAggInfo *mminfo,
 	subroot->query_level++;
 	subroot->parent_root = root;
 	subroot->plan_name = choose_plan_name(root->glob, "minmax", true);
+	remember_plannerinfo(subroot);
 
 	/* reset subplan-related stuff */
 	subroot->plan_params = NIL;
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index fd77334e5fd..47b32b20e1a 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -745,6 +745,9 @@ subquery_planner(PlannerGlobal *glob, Query *parse, char *plan_name,
 		root->wt_param_id = -1;
 	root->non_recursive_path = NULL;
 
+	/* Add this PlanenrInfo to the PlannerGlobal's list */
+	remember_plannerinfo(root);
+
 	/*
 	 * Create the top-level join domain.  This won't have valid contents until
 	 * deconstruct_jointree fills it in, but the node needs to exist before
@@ -8968,6 +8971,18 @@ choose_plan_name(PlannerGlobal *glob, const char *name, bool always_number)
 {
 	unsigned	n;
 
+#ifdef USE_ASSERT_CHECKING
+	Assert(list_length(glob->allroots) == list_length(glob->subplanNames) + 1);
+	foreach_ptr(char, subplan_name, glob->subplanNames)
+	{
+		PlannerInfo *subroot;
+
+		subroot = list_nth(glob->allroots,
+						   foreach_current_index(subplan_name) + 1);
+		Assert(strcmp(subroot->plan_name, subplan_name) == 0);
+	}
+#endif
+
 	/*
 	 * If a numeric suffix is not required, then search the list of
 	 * previously-assigned names for a match. If none is found, then we can
@@ -8977,9 +8992,10 @@ choose_plan_name(PlannerGlobal *glob, const char *name, bool always_number)
 	{
 		bool		found = false;
 
-		foreach_ptr(char, subplan_name, glob->subplanNames)
+		foreach_ptr(PlannerInfo, subroot, glob->allroots)
 		{
-			if (strcmp(subplan_name, name) == 0)
+			if (subroot->plan_name != NULL &&
+				strcmp(subroot->plan_name, name) == 0)
 			{
 				found = true;
 				break;
@@ -9006,9 +9022,10 @@ choose_plan_name(PlannerGlobal *glob, const char *name, bool always_number)
 		char	   *proposed_name = psprintf("%s_%u", name, n);
 		bool		found = false;
 
-		foreach_ptr(char, subplan_name, glob->subplanNames)
+		foreach_ptr(PlannerInfo, subroot, glob->allroots)
 		{
-			if (strcmp(subplan_name, proposed_name) == 0)
+			if (subroot->plan_name != NULL &&
+				strcmp(subroot->plan_name, proposed_name) == 0)
 			{
 				found = true;
 				break;
@@ -9024,3 +9041,28 @@ choose_plan_name(PlannerGlobal *glob, const char *name, bool always_number)
 		pfree(proposed_name);
 	}
 }
+
+/*
+ * Add a new PlannerInfo to the PlannerGlobal's list of all subroots.
+ */
+void
+remember_plannerinfo(PlannerInfo *newroot)
+{
+	PlannerGlobal *glob = newroot->glob;
+
+#ifdef USE_ASSERT_CHECKING
+	/* Only the first PlannerInfo should be nameless. */
+	Assert(newroot->plan_name != NULL || glob->allroots == NIL);
+
+	/* PlannerInfo names should not be duplicated. */
+	foreach_node(PlannerInfo, root, glob->allroots)
+	{
+		if (root->plan_name == NULL)
+			continue;
+		Assert(strcmp(root->plan_name, newroot->plan_name) != 0);
+	}
+#endif
+
+	/* Add new PlannerInfo to list. */
+	glob->allroots = lappend(glob->allroots, newroot);
+}
diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c
index 7581695647d..86e1abe8524 100644
--- a/src/backend/optimizer/prep/prepjointree.c
+++ b/src/backend/optimizer/prep/prepjointree.c
@@ -1350,6 +1350,13 @@ pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
 	/*
 	 * Create a PlannerInfo data structure for this subquery.
 	 *
+	 * Unlike subquery_planner, the subroot we create here is only transient.
+	 * It inherits properties such as the query_level, plan_name, and
+	 * parent_root from the supplied root, rather than becoming a new query
+	 * level. Whether we succeed or fail in pulling up the subquery, this
+	 * subroot won't survive long-term and shouldn't be linked into any
+	 * long-lived planner data structures.
+	 *
 	 * NOTE: the next few steps should match the first processing in
 	 * subquery_planner().  Can we refactor to avoid code duplication, or
 	 * would that just make things uglier?
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index 46a8655621d..2707ca50019 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -110,6 +110,9 @@ typedef struct PlannerGlobal
 	/* PlannerInfos for SubPlan nodes */
 	List	   *subroots pg_node_attr(read_write_ignore);
 
+	/* every non-transient PlannerInfo (superset of subroots) */
+	List	   *allroots pg_node_attr(read_write_ignore);
+
 	/* names already used for subplans (list of C strings) */
 	List	   *subplanNames pg_node_attr(read_write_ignore);
 
diff --git a/src/include/optimizer/planner.h b/src/include/optimizer/planner.h
index 55d9b7940aa..76a7b7e9a2a 100644
--- a/src/include/optimizer/planner.h
+++ b/src/include/optimizer/planner.h
@@ -82,5 +82,6 @@ extern RelOptInfo *create_unique_paths(PlannerInfo *root, RelOptInfo *rel,
 
 extern char *choose_plan_name(PlannerGlobal *glob, const char *name,
 							  bool always_number);
+extern void remember_plannerinfo(PlannerInfo *newroot);
 
 #endif							/* PLANNER_H */
-- 
2.51.0