v36-0011-Track-which-relations-are-modified-by-a-query.patch

From 9f7098111d8520a955b0b4d6d4d62c4a79a5497c Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Wed, 3 Dec 2025 15:07:24 -0500
Subject: [PATCH v36 11/16] Track which relations are modified by a query

Save the relids in a bitmap in the estate. A later commit will pass this
information down to scan nodes to control whether or not the scan allows
setting the visibility map while on-access pruning. We don't want to set
the visibility map if the query is just going to modify the page
immediately after.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/F5CDD1B5-628C-44A1-9F85-3958C626F6A9%40gmail.com
---
 src/backend/executor/execMain.c  | 18 ++++++++++++++++++
 src/backend/executor/execUtils.c | 31 +++++++++++++++++++++++++++++++
 src/include/executor/executor.h  |  3 +++
 src/include/nodes/execnodes.h    |  6 ++++++
 4 files changed, 58 insertions(+)

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index bfd3ebc601e..57dcdeda056 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -920,6 +920,10 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 					break;
 			}
 
+			/* If it has a rowmark, the relation may be modified */
+			estate->es_modified_relids = bms_add_member(estate->es_modified_relids,
+														rc->rti);
+
 			/* Check that relation is a legal target for marking */
 			if (relation)
 				CheckValidRowMarkRel(relation, rc->markType);
@@ -990,6 +994,10 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 	 */
 	planstate = ExecInitNode(plan, estate, eflags);
 
+#ifdef USE_ASSERT_CHECKING
+	CrossCheckModifiedRelids(estate);
+#endif
+
 	/*
 	 * Get the tuple descriptor describing the type of tuples to return.
 	 */
@@ -3033,6 +3041,12 @@ EvalPlanQualStart(EPQState *epqstate, Plan *planTree)
 	rcestate->es_output_cid = parentestate->es_output_cid;
 	rcestate->es_queryEnv = parentestate->es_queryEnv;
 
+	/*
+	 * Use a deep copy to avoid stale pointers since bms_add_member() may
+	 * reallocate the bitmap.
+	 */
+	rcestate->es_modified_relids = bms_copy(parentestate->es_modified_relids);
+
 	/*
 	 * ResultRelInfos needed by subplans are initialized from scratch when the
 	 * subplans themselves are initialized.
@@ -3165,6 +3179,10 @@ EvalPlanQualStart(EPQState *epqstate, Plan *planTree)
 	 */
 	epqstate->recheckplanstate = ExecInitNode(planTree, rcestate, 0);
 
+#ifdef USE_ASSERT_CHECKING
+	CrossCheckModifiedRelids(rcestate);
+#endif
+
 	MemoryContextSwitchTo(oldcontext);
 }
 
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index cd4d5452cfb..0f8364b8720 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -123,6 +123,8 @@ CreateExecutorState(void)
 	estate->es_part_prune_results = NIL;
 	estate->es_unpruned_relids = NULL;
 
+	estate->es_modified_relids = NULL;
+
 	estate->es_junkFilter = NULL;
 
 	estate->es_output_cid = (CommandId) 0;
@@ -871,6 +873,33 @@ ExecGetRangeTableRelation(EState *estate, Index rti, bool isResultRel)
 	return rel;
 }
 
+#ifdef USE_ASSERT_CHECKING
+/*
+ * Assert that es_modified_relids includes all potentially modified RT
+ * indexes.
+ */
+void
+CrossCheckModifiedRelids(EState *estate)
+{
+	Bitmapset  *expected = NULL;
+	ListCell   *lc;
+
+	foreach(lc, estate->es_opened_result_relations)
+	{
+		ResultRelInfo *rri = lfirst_node(ResultRelInfo, lc);
+
+		expected = bms_add_member(expected, rri->ri_RangeTableIndex);
+	}
+	if (estate->es_rowmarks)
+	{
+		for (Index rti = 1; rti <= estate->es_range_table_size; rti++)
+			if (estate->es_rowmarks[rti - 1] != NULL)
+				expected = bms_add_member(expected, rti);
+	}
+	Assert(bms_is_subset(expected, estate->es_modified_relids));
+}
+#endif
+
 /*
  * ExecInitResultRelation
  *		Open relation given by the passed-in RT index and fill its
@@ -896,6 +925,8 @@ ExecInitResultRelation(EState *estate, ResultRelInfo *resultRelInfo,
 		estate->es_result_relations = (ResultRelInfo **)
 			palloc0(estate->es_range_table_size * sizeof(ResultRelInfo *));
 	estate->es_result_relations[rti - 1] = resultRelInfo;
+	estate->es_modified_relids = bms_add_member(estate->es_modified_relids,
+												rti);
 
 	/*
 	 * Saving in the list allows to avoid needlessly traversing the whole
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index d46ba59895d..05f032baeaa 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -703,6 +703,9 @@ extern Relation ExecGetRangeTableRelation(EState *estate, Index rti,
 										  bool isResultRel);
 extern void ExecInitResultRelation(EState *estate, ResultRelInfo *resultRelInfo,
 								   Index rti);
+#ifdef USE_ASSERT_CHECKING
+extern void CrossCheckModifiedRelids(EState *estate);
+#endif
 
 extern int	executor_errposition(EState *estate, int location);
 
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 63c067d5aae..610385df12b 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -679,6 +679,12 @@ typedef struct EState
 									 * ExecDoInitialPruning() */
 	const char *es_sourceText;	/* Source text from QueryDesc */
 
+	/*
+	 * RT indexes of relations modified by the query through a
+	 * UPDATE/DELETE/INSERT/MERGE or targeted by a SELECT FOR UPDATE.
+	 */
+	Bitmapset  *es_modified_relids;
+
 	JunkFilter *es_junkFilter;	/* top-level junk filter, if any */
 
 	/* If query can insert/delete tuples, the command ID to mark them with */
-- 
2.43.0