v38-0010-Pass-down-information-on-table-modification-to-s.patch

From 3a6b08fc3219afd79dc81a5219e6a543d67036f6 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Mon, 2 Mar 2026 16:31:33 -0500
Subject: [PATCH v38 10/12] Pass down information on table modification to scan
 node

Pass down information to sequential scan, index [only] scan, bitmap
table scan, sample scan, and TID range scan nodes on whether or not the
query modifies the relation being scanned. A later commit will use this
information to update the VM during on-access pruning only if the
relation is not modified by the query.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Andrey Borodin <x4mmm@yandex-team.ru>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/4379FDA3-9446-4E2C-9C15-32EFE8D4F31B%40yandex-team.ru
---
 src/backend/access/heap/heapam_handler.c  |  1 +
 src/backend/executor/nodeBitmapHeapscan.c |  9 ++++++-
 src/backend/executor/nodeIndexonlyscan.c  | 25 +++++++++++++++---
 src/backend/executor/nodeIndexscan.c      | 32 ++++++++++++++++++++---
 src/backend/executor/nodeSamplescan.c     |  8 +++++-
 src/backend/executor/nodeSeqscan.c        | 26 +++++++++++++++---
 src/backend/executor/nodeTidrangescan.c   | 24 ++++++++++++++---
 src/include/access/heapam.h               |  6 +++++
 src/include/access/tableam.h              |  3 +++
 9 files changed, 119 insertions(+), 15 deletions(-)

diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index 6122603d11e..d35b688d751 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -86,6 +86,7 @@ heapam_index_fetch_begin(Relation rel, uint32 flags)
 	hscan->xs_base.rel = rel;
 	hscan->xs_cbuf = InvalidBuffer;
 	hscan->xs_vmbuffer = InvalidBuffer;
+	hscan->modifies_base_rel = !(flags & SO_HINT_REL_READ_ONLY);
 
 	return &hscan->xs_base;
 }
diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index 620fc7e259a..a5ab5e2b37f 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -104,11 +104,18 @@ BitmapTableScanSetup(BitmapHeapScanState *node)
 	 */
 	if (!node->ss.ss_currentScanDesc)
 	{
+		uint32		flags = 0;
+
+		if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+						   node->ss.ps.state->es_modified_relids))
+			flags |= SO_HINT_REL_READ_ONLY;
+
 		node->ss.ss_currentScanDesc =
 			table_beginscan_bm(node->ss.ss_currentRelation,
 							   node->ss.ps.state->es_snapshot,
 							   0,
-							   NULL, 0);
+							   NULL,
+							   flags);
 	}
 
 	node->ss.ss_currentScanDesc->st.rs_tbmiterator = tbmiterator;
diff --git a/src/backend/executor/nodeIndexonlyscan.c b/src/backend/executor/nodeIndexonlyscan.c
index aefb792ee6e..6d7a32c1cb8 100644
--- a/src/backend/executor/nodeIndexonlyscan.c
+++ b/src/backend/executor/nodeIndexonlyscan.c
@@ -84,6 +84,12 @@ IndexOnlyNext(IndexOnlyScanState *node)
 
 	if (scandesc == NULL)
 	{
+		uint32		flags = 0;
+
+		if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+						   estate->es_modified_relids))
+			flags |= SO_HINT_REL_READ_ONLY;
+
 		/*
 		 * We reach here if the index only scan is not parallel, or if we're
 		 * serially executing an index only scan that was planned to be
@@ -94,7 +100,8 @@ IndexOnlyNext(IndexOnlyScanState *node)
 								   estate->es_snapshot,
 								   &node->ioss_Instrument,
 								   node->ioss_NumScanKeys,
-								   node->ioss_NumOrderByKeys, 0);
+								   node->ioss_NumOrderByKeys,
+								   flags);
 
 		node->ioss_ScanDesc = scandesc;
 
@@ -761,6 +768,7 @@ ExecIndexOnlyScanInitializeDSM(IndexOnlyScanState *node,
 	ParallelIndexScanDesc piscan;
 	bool		instrument = node->ss.ps.instrument != NULL;
 	bool		parallel_aware = node->ss.ps.plan->parallel_aware;
+	uint32		flags = 0;
 
 	if (!instrument && !parallel_aware)
 	{
@@ -782,13 +790,18 @@ ExecIndexOnlyScanInitializeDSM(IndexOnlyScanState *node,
 		return;
 	}
 
+	if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+					   estate->es_modified_relids))
+		flags |= SO_HINT_REL_READ_ONLY;
+
 	node->ioss_ScanDesc =
 		index_beginscan_parallel(node->ss.ss_currentRelation,
 								 node->ioss_RelationDesc,
 								 &node->ioss_Instrument,
 								 node->ioss_NumScanKeys,
 								 node->ioss_NumOrderByKeys,
-								 piscan, 0);
+								 piscan, flags);
+
 	node->ioss_ScanDesc->xs_want_itup = true;
 	node->ioss_VMBuffer = InvalidBuffer;
 
@@ -829,6 +842,7 @@ ExecIndexOnlyScanInitializeWorker(IndexOnlyScanState *node,
 	ParallelIndexScanDesc piscan;
 	bool		instrument = node->ss.ps.instrument != NULL;
 	bool		parallel_aware = node->ss.ps.plan->parallel_aware;
+	uint32		flags = 0;
 
 	if (!instrument && !parallel_aware)
 	{
@@ -848,13 +862,18 @@ ExecIndexOnlyScanInitializeWorker(IndexOnlyScanState *node,
 		return;
 	}
 
+	if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+					   node->ss.ps.state->es_modified_relids))
+		flags |= SO_HINT_REL_READ_ONLY;
+
 	node->ioss_ScanDesc =
 		index_beginscan_parallel(node->ss.ss_currentRelation,
 								 node->ioss_RelationDesc,
 								 &node->ioss_Instrument,
 								 node->ioss_NumScanKeys,
 								 node->ioss_NumOrderByKeys,
-								 piscan, 0);
+								 piscan, flags);
+
 	node->ioss_ScanDesc->xs_want_itup = true;
 
 	/*
diff --git a/src/backend/executor/nodeIndexscan.c b/src/backend/executor/nodeIndexscan.c
index 477cd4fcf99..52b7fc46593 100644
--- a/src/backend/executor/nodeIndexscan.c
+++ b/src/backend/executor/nodeIndexscan.c
@@ -102,6 +102,12 @@ IndexNext(IndexScanState *node)
 
 	if (scandesc == NULL)
 	{
+		uint32		flags = 0;
+
+		if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+						   estate->es_modified_relids))
+			flags |= SO_HINT_REL_READ_ONLY;
+
 		/*
 		 * We reach here if the index scan is not parallel, or if we're
 		 * serially executing an index scan that was planned to be parallel.
@@ -111,7 +117,8 @@ IndexNext(IndexScanState *node)
 								   estate->es_snapshot,
 								   &node->iss_Instrument,
 								   node->iss_NumScanKeys,
-								   node->iss_NumOrderByKeys, 0);
+								   node->iss_NumOrderByKeys,
+								   flags);
 
 		node->iss_ScanDesc = scandesc;
 
@@ -198,6 +205,12 @@ IndexNextWithReorder(IndexScanState *node)
 
 	if (scandesc == NULL)
 	{
+		uint32		flags = 0;
+
+		if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+						   estate->es_modified_relids))
+			flags |= SO_HINT_REL_READ_ONLY;
+
 		/*
 		 * We reach here if the index scan is not parallel, or if we're
 		 * serially executing an index scan that was planned to be parallel.
@@ -207,7 +220,8 @@ IndexNextWithReorder(IndexScanState *node)
 								   estate->es_snapshot,
 								   &node->iss_Instrument,
 								   node->iss_NumScanKeys,
-								   node->iss_NumOrderByKeys, 0);
+								   node->iss_NumOrderByKeys,
+								   flags);
 
 		node->iss_ScanDesc = scandesc;
 
@@ -1696,6 +1710,7 @@ ExecIndexScanInitializeDSM(IndexScanState *node,
 	ParallelIndexScanDesc piscan;
 	bool		instrument = node->ss.ps.instrument != NULL;
 	bool		parallel_aware = node->ss.ps.plan->parallel_aware;
+	uint32		flags = 0;
 
 	if (!instrument && !parallel_aware)
 	{
@@ -1717,13 +1732,17 @@ ExecIndexScanInitializeDSM(IndexScanState *node,
 		return;
 	}
 
+	if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+					   estate->es_modified_relids))
+		flags |= SO_HINT_REL_READ_ONLY;
+
 	node->iss_ScanDesc =
 		index_beginscan_parallel(node->ss.ss_currentRelation,
 								 node->iss_RelationDesc,
 								 &node->iss_Instrument,
 								 node->iss_NumScanKeys,
 								 node->iss_NumOrderByKeys,
-								 piscan, 0);
+								 piscan, flags);
 
 	/*
 	 * If no run-time keys to calculate or they are ready, go ahead and pass
@@ -1762,6 +1781,7 @@ ExecIndexScanInitializeWorker(IndexScanState *node,
 	ParallelIndexScanDesc piscan;
 	bool		instrument = node->ss.ps.instrument != NULL;
 	bool		parallel_aware = node->ss.ps.plan->parallel_aware;
+	uint32		flags = 0;
 
 	if (!instrument && !parallel_aware)
 	{
@@ -1781,13 +1801,17 @@ ExecIndexScanInitializeWorker(IndexScanState *node,
 		return;
 	}
 
+	if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+					   node->ss.ps.state->es_modified_relids))
+		flags |= SO_HINT_REL_READ_ONLY;
+
 	node->iss_ScanDesc =
 		index_beginscan_parallel(node->ss.ss_currentRelation,
 								 node->iss_RelationDesc,
 								 &node->iss_Instrument,
 								 node->iss_NumScanKeys,
 								 node->iss_NumOrderByKeys,
-								 piscan, 0);
+								 piscan, flags);
 
 	/*
 	 * If no run-time keys to calculate or they are ready, go ahead and pass
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
index 47660baf2fa..62eff19bc4f 100644
--- a/src/backend/executor/nodeSamplescan.c
+++ b/src/backend/executor/nodeSamplescan.c
@@ -291,13 +291,19 @@ tablesample_init(SampleScanState *scanstate)
 	/* Now we can create or reset the HeapScanDesc */
 	if (scanstate->ss.ss_currentScanDesc == NULL)
 	{
+		uint32		flags = 0;
+
+		if (!bms_is_member(((Scan *) scanstate->ss.ps.plan)->scanrelid,
+						   scanstate->ss.ps.state->es_modified_relids))
+			flags |= SO_HINT_REL_READ_ONLY;
+
 		scanstate->ss.ss_currentScanDesc =
 			table_beginscan_sampling(scanstate->ss.ss_currentRelation,
 									 scanstate->ss.ps.state->es_snapshot,
 									 0, NULL,
 									 scanstate->use_bulkread,
 									 allow_sync,
-									 scanstate->use_pagemode, 0);
+									 scanstate->use_pagemode, flags);
 	}
 	else
 	{
diff --git a/src/backend/executor/nodeSeqscan.c b/src/backend/executor/nodeSeqscan.c
index d9d7ec0516a..65349ea9c54 100644
--- a/src/backend/executor/nodeSeqscan.c
+++ b/src/backend/executor/nodeSeqscan.c
@@ -65,13 +65,20 @@ SeqNext(SeqScanState *node)
 
 	if (scandesc == NULL)
 	{
+		uint32		flags = 0;
+
+		if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+						   estate->es_modified_relids))
+			flags |= SO_HINT_REL_READ_ONLY;
+
 		/*
 		 * We reach here if the scan is not parallel, or if we're serially
 		 * executing a scan that was planned to be parallel.
 		 */
 		scandesc = table_beginscan(node->ss.ss_currentRelation,
 								   estate->es_snapshot,
-								   0, NULL, 0);
+								   0, NULL, flags);
+
 		node->ss.ss_currentScanDesc = scandesc;
 	}
 
@@ -367,14 +374,20 @@ ExecSeqScanInitializeDSM(SeqScanState *node,
 {
 	EState	   *estate = node->ss.ps.state;
 	ParallelTableScanDesc pscan;
+	uint32		flags = 0;
 
 	pscan = shm_toc_allocate(pcxt->toc, node->pscan_len);
 	table_parallelscan_initialize(node->ss.ss_currentRelation,
 								  pscan,
 								  estate->es_snapshot);
 	shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, pscan);
+	if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+					   estate->es_modified_relids))
+		flags |= SO_HINT_REL_READ_ONLY;
+
 	node->ss.ss_currentScanDesc =
-		table_beginscan_parallel(node->ss.ss_currentRelation, pscan, 0);
+		table_beginscan_parallel(node->ss.ss_currentRelation, pscan,
+								 flags);
 }
 
 /* ----------------------------------------------------------------
@@ -404,8 +417,15 @@ ExecSeqScanInitializeWorker(SeqScanState *node,
 							ParallelWorkerContext *pwcxt)
 {
 	ParallelTableScanDesc pscan;
+	uint32		flags = 0;
+
+	if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+					   node->ss.ps.state->es_modified_relids))
+		flags |= SO_HINT_REL_READ_ONLY;
 
 	pscan = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
 	node->ss.ss_currentScanDesc =
-		table_beginscan_parallel(node->ss.ss_currentRelation, pscan, 0);
+		table_beginscan_parallel(node->ss.ss_currentRelation,
+								 pscan,
+								 flags);
 }
diff --git a/src/backend/executor/nodeTidrangescan.c b/src/backend/executor/nodeTidrangescan.c
index 461edb8893b..7fbdf401734 100644
--- a/src/backend/executor/nodeTidrangescan.c
+++ b/src/backend/executor/nodeTidrangescan.c
@@ -242,10 +242,16 @@ TidRangeNext(TidRangeScanState *node)
 
 		if (scandesc == NULL)
 		{
+			uint32		flags = 0;
+
+			if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+							   estate->es_modified_relids))
+				flags |= SO_HINT_REL_READ_ONLY;
+
 			scandesc = table_beginscan_tidrange(node->ss.ss_currentRelation,
 												estate->es_snapshot,
 												&node->trss_mintid,
-												&node->trss_maxtid, 0);
+												&node->trss_maxtid, flags);
 			node->ss.ss_currentScanDesc = scandesc;
 		}
 		else
@@ -451,15 +457,21 @@ ExecTidRangeScanInitializeDSM(TidRangeScanState *node, ParallelContext *pcxt)
 {
 	EState	   *estate = node->ss.ps.state;
 	ParallelTableScanDesc pscan;
+	uint32		flags = 0;
 
 	pscan = shm_toc_allocate(pcxt->toc, node->trss_pscanlen);
 	table_parallelscan_initialize(node->ss.ss_currentRelation,
 								  pscan,
 								  estate->es_snapshot);
 	shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, pscan);
+
+	if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+					   estate->es_modified_relids))
+		flags |= SO_HINT_REL_READ_ONLY;
+
 	node->ss.ss_currentScanDesc =
 		table_beginscan_parallel_tidrange(node->ss.ss_currentRelation,
-										  pscan, 0);
+										  pscan, flags);
 }
 
 /* ----------------------------------------------------------------
@@ -489,9 +501,15 @@ ExecTidRangeScanInitializeWorker(TidRangeScanState *node,
 								 ParallelWorkerContext *pwcxt)
 {
 	ParallelTableScanDesc pscan;
+	uint32		flags = 0;
 
 	pscan = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
+
+	if (!bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+					   node->ss.ps.state->es_modified_relids))
+		flags |= SO_HINT_REL_READ_ONLY;
+
 	node->ss.ss_currentScanDesc =
 		table_beginscan_parallel_tidrange(node->ss.ss_currentRelation,
-										  pscan, 0);
+										  pscan, flags);
 }
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index c2621dc2fac..978ea90ffa2 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -131,6 +131,12 @@ typedef struct IndexFetchHeapData
 
 	/* Current heap block's corresponding page in the visibility map */
 	Buffer		xs_vmbuffer;
+
+	/*
+	 * Some optimizations can only be performed if the query does not modify
+	 * the underlying relation. Track that here.
+	 */
+	bool		modifies_base_rel;
 } IndexFetchHeapData;
 
 /* Result codes for HeapTupleSatisfiesVacuum */
diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
index f1065e30638..57ce94a386f 100644
--- a/src/include/access/tableam.h
+++ b/src/include/access/tableam.h
@@ -63,6 +63,9 @@ typedef enum ScanOptions
 
 	/* unregister snapshot at scan end? */
 	SO_TEMP_SNAPSHOT = 1 << 9,
+
+	/* set if the query doesn't modify the relation */
+	SO_HINT_REL_READ_ONLY = 1 << 10,
 }			ScanOptions;
 
 /*
-- 
2.43.0