v15-0022-Allow-on-access-pruning-to-set-pages-all-visible.patch

From 8df8cf1d9c5baa8d07e623e80dfaeb5ff4b25228 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Tue, 29 Jul 2025 14:34:30 -0400
Subject: [PATCH v15 22/23] Allow on-access pruning to set pages all-visible

Many queries do not modify the underlying relation. For such queries, if
on-access pruning occurs during the scan, we can check whether the page
has become all-visible and update the visibility map accordingly.
Previously, only vacuum marked pages as all-visible or all-frozen.

Supporting this requires passing information about whether the relation
is modified from the executor down to the scan descriptor.

This commit implements on-access VM setting for sequential scans as well
as for the underlying heap relation in index scans and bitmap heap
scans.
---
 src/backend/access/heap/heapam.c              | 15 +++-
 src/backend/access/heap/heapam_handler.c      | 15 +++-
 src/backend/access/heap/pruneheap.c           | 89 ++++++++++++++-----
 src/backend/access/index/indexam.c            | 46 ++++++++++
 src/backend/access/table/tableam.c            | 39 +++++++-
 src/backend/executor/execMain.c               |  4 +
 src/backend/executor/execUtils.c              |  2 +
 src/backend/executor/nodeBitmapHeapscan.c     |  7 +-
 src/backend/executor/nodeIndexscan.c          | 18 ++--
 src/backend/executor/nodeSeqscan.c            | 24 +++--
 src/include/access/genam.h                    | 11 +++
 src/include/access/heapam.h                   | 24 ++++-
 src/include/access/relscan.h                  |  6 ++
 src/include/access/tableam.h                  | 30 ++++++-
 src/include/nodes/execnodes.h                 |  6 ++
 .../t/035_standby_logical_decoding.pl         |  3 +-
 16 files changed, 292 insertions(+), 47 deletions(-)

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 14a2996b9ee..6181e355aaf 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -555,6 +555,7 @@ heap_prepare_pagescan(TableScanDesc sscan)
 	Buffer		buffer = scan->rs_cbuf;
 	BlockNumber block = scan->rs_cblock;
 	Snapshot	snapshot;
+	Buffer	   *vmbuffer = NULL;
 	Page		page;
 	int			lines;
 	bool		all_visible;
@@ -569,7 +570,9 @@ heap_prepare_pagescan(TableScanDesc sscan)
 	/*
 	 * Prune and repair fragmentation for the whole page, if possible.
 	 */
-	heap_page_prune_opt(scan->rs_base.rs_rd, buffer);
+	if (sscan->rs_flags & SO_ALLOW_VM_SET)
+		vmbuffer = &scan->rs_vmbuffer;
+	heap_page_prune_opt(scan->rs_base.rs_rd, buffer, vmbuffer);
 
 	/*
 	 * We must hold share lock on the buffer content while examining tuple
@@ -1246,6 +1249,7 @@ heap_beginscan(Relation relation, Snapshot snapshot,
 														  sizeof(TBMIterateResult));
 	}
 
+	scan->rs_vmbuffer = InvalidBuffer;
 
 	return (TableScanDesc) scan;
 }
@@ -1284,6 +1288,12 @@ heap_rescan(TableScanDesc sscan, ScanKey key, bool set_params,
 		scan->rs_cbuf = InvalidBuffer;
 	}
 
+	if (BufferIsValid(scan->rs_vmbuffer))
+	{
+		ReleaseBuffer(scan->rs_vmbuffer);
+		scan->rs_vmbuffer = InvalidBuffer;
+	}
+
 	/*
 	 * SO_TYPE_BITMAPSCAN would be cleaned up here, but it does not hold any
 	 * additional data vs a normal HeapScan
@@ -1316,6 +1326,9 @@ heap_endscan(TableScanDesc sscan)
 	if (BufferIsValid(scan->rs_cbuf))
 		ReleaseBuffer(scan->rs_cbuf);
 
+	if (BufferIsValid(scan->rs_vmbuffer))
+		ReleaseBuffer(scan->rs_vmbuffer);
+
 	/*
 	 * Must free the read stream before freeing the BufferAccessStrategy.
 	 */
diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index bcbac844bb6..f05b9e4968d 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -85,6 +85,7 @@ heapam_index_fetch_begin(Relation rel)
 
 	hscan->xs_base.rel = rel;
 	hscan->xs_cbuf = InvalidBuffer;
+	hscan->xs_vmbuffer = InvalidBuffer;
 
 	return &hscan->xs_base;
 }
@@ -99,6 +100,12 @@ heapam_index_fetch_reset(IndexFetchTableData *scan)
 		ReleaseBuffer(hscan->xs_cbuf);
 		hscan->xs_cbuf = InvalidBuffer;
 	}
+
+	if (BufferIsValid(hscan->xs_vmbuffer))
+	{
+		ReleaseBuffer(hscan->xs_vmbuffer);
+		hscan->xs_vmbuffer = InvalidBuffer;
+	}
 }
 
 static void
@@ -138,7 +145,8 @@ heapam_index_fetch_tuple(struct IndexFetchTableData *scan,
 		 * Prune page, but only if we weren't already on this page
 		 */
 		if (prev_buf != hscan->xs_cbuf)
-			heap_page_prune_opt(hscan->xs_base.rel, hscan->xs_cbuf);
+			heap_page_prune_opt(hscan->xs_base.rel, hscan->xs_cbuf,
+								scan->modifies_base_rel ? NULL : &hscan->xs_vmbuffer);
 	}
 
 	/* Obtain share-lock on the buffer so we can examine visibility */
@@ -2471,6 +2479,7 @@ BitmapHeapScanNextBlock(TableScanDesc scan,
 	TBMIterateResult *tbmres;
 	OffsetNumber offsets[TBM_MAX_TUPLES_PER_PAGE];
 	int			noffsets = -1;
+	Buffer	   *vmbuffer = NULL;
 
 	Assert(scan->rs_flags & SO_TYPE_BITMAPSCAN);
 	Assert(hscan->rs_read_stream);
@@ -2517,7 +2526,9 @@ BitmapHeapScanNextBlock(TableScanDesc scan,
 	/*
 	 * Prune and repair fragmentation for the whole page, if possible.
 	 */
-	heap_page_prune_opt(scan->rs_rd, buffer);
+	if (scan->rs_flags & SO_ALLOW_VM_SET)
+		vmbuffer = &hscan->rs_vmbuffer;
+	heap_page_prune_opt(scan->rs_rd, buffer, vmbuffer);
 
 	/*
 	 * We must hold share lock on the buffer content while examining tuple
diff --git a/src/backend/access/heap/pruneheap.c b/src/backend/access/heap/pruneheap.c
index e64addfdf5d..0d8fea346c5 100644
--- a/src/backend/access/heap/pruneheap.c
+++ b/src/backend/access/heap/pruneheap.c
@@ -45,6 +45,8 @@ typedef struct
 	bool		mark_unused_now;
 	/* whether to attempt freezing tuples */
 	bool		attempt_freeze;
+	/* whether or not to attempt updating the VM */
+	bool		attempt_update_vm;
 	const struct VacuumCutoffs *cutoffs;
 
 	/*-------------------------------------------------------
@@ -185,9 +187,13 @@ static void page_verify_redirects(Page page);
  * if there's not any use in pruning.
  *
  * Caller must have pin on the buffer, and must *not* have a lock on it.
+ *
+ * If vmbuffer is not NULL, it is okay for pruning to set the visibility map if
+ * the page is all visible. We will take care of pinning and, if needed,
+ * reading in the page of the visibility map.
  */
 void
-heap_page_prune_opt(Relation relation, Buffer buffer)
+heap_page_prune_opt(Relation relation, Buffer buffer, Buffer *vmbuffer)
 {
 	Page		page = BufferGetPage(buffer);
 	TransactionId prune_xid;
@@ -251,6 +257,13 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
 		{
 			OffsetNumber dummy_off_loc;
 			PruneFreezeResult presult;
+			int			options = 0;
+
+			if (vmbuffer)
+			{
+				visibilitymap_pin(relation, BufferGetBlockNumber(buffer), vmbuffer);
+				options = HEAP_PAGE_PRUNE_UPDATE_VIS;
+			}
 
 			/*
 			 * For now, pass mark_unused_now as false regardless of whether or
@@ -258,8 +271,9 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
 			 * that during on-access pruning with the current implementation.
 			 */
 			heap_page_prune_and_freeze(relation, buffer,
-									   InvalidBuffer, false,
-									   PRUNE_ON_ACCESS, 0, NULL,
+									   vmbuffer ? *vmbuffer : InvalidBuffer,
+									   false,	/* blk_known_av */
+									   PRUNE_ON_ACCESS, options, NULL,
 									   vistest, &presult, &dummy_off_loc, NULL, NULL);
 
 			/*
@@ -443,6 +457,8 @@ heap_page_will_set_vis(Relation relation,
 					   Buffer heap_buf,
 					   Buffer vmbuffer,
 					   bool blk_known_av,
+					   PruneReason reason,
+					   bool do_prune, bool do_freeze,
 					   PruneState *prstate,
 					   uint8 *vmflags,
 					   bool *do_set_pd_vis)
@@ -450,6 +466,32 @@ heap_page_will_set_vis(Relation relation,
 	Page		heap_page = BufferGetPage(heap_buf);
 	bool		do_set_vm = false;
 
+	*do_set_pd_vis = false;
+
+	if (!prstate->attempt_update_vm)
+	{
+		Assert(!prstate->all_visible && !prstate->all_frozen);
+		Assert(*vmflags == 0);
+		return false;
+	}
+
+	/*
+	 * If this is an on-access call and we're not actually pruning, avoid
+	 * setting the visibility map if it would newly dirty the heap page or, if
+	 * the page is already dirty, if doing so would require including a
+	 * full-page image (FPI) of the heap page in the WAL. This situation
+	 * should be rare, as on-access pruning is only attempted when
+	 * pd_prune_xid is valid.
+	 */
+	if (reason == PRUNE_ON_ACCESS &&
+		prstate->all_visible &&
+		!do_prune && !do_freeze &&
+		(!BufferIsDirty(heap_buf) || XLogCheckBufferNeedsBackup(heap_buf)))
+	{
+		prstate->all_visible = prstate->all_frozen = false;
+		return false;
+	}
+
 	if (prstate->all_visible && !PageIsAllVisible(heap_page))
 		*do_set_pd_vis = true;
 
@@ -473,6 +515,9 @@ heap_page_will_set_vis(Relation relation,
 	 * page-level bit is clear.  However, it's possible that in vacuum the bit
 	 * got cleared after heap_vac_scan_next_block() was called, so we must
 	 * recheck with buffer lock before concluding that the VM is corrupt.
+	 *
+	 * XXX: This will never trigger for on-access pruning because it passes
+	 * blk_known_av as false. Should we remove that condition here?
 	 */
 	else if (blk_known_av && !PageIsAllVisible(heap_page) &&
 			 visibilitymap_get_status(relation, heap_blk, &vmbuffer) != 0)
@@ -615,6 +660,7 @@ heap_page_prune_and_freeze(Relation relation, Buffer buffer,
 	prstate.vistest = vistest;
 	prstate.mark_unused_now = (options & HEAP_PAGE_PRUNE_MARK_UNUSED_NOW) != 0;
 	prstate.attempt_freeze = (options & HEAP_PAGE_PRUNE_FREEZE) != 0;
+	prstate.attempt_update_vm = (options & HEAP_PAGE_PRUNE_UPDATE_VIS) != 0;
 	prstate.cutoffs = cutoffs;
 
 	/*
@@ -692,7 +738,7 @@ heap_page_prune_and_freeze(Relation relation, Buffer buffer,
 		prstate.all_visible = true;
 		prstate.all_frozen = true;
 	}
-	else if ((options & HEAP_PAGE_PRUNE_UPDATE_VIS) != 0)
+	else if (prstate.attempt_update_vm)
 	{
 		prstate.all_visible = true;
 		prstate.all_frozen = false;
@@ -906,6 +952,14 @@ heap_page_prune_and_freeze(Relation relation, Buffer buffer,
 		prstate.ndead > 0 ||
 		prstate.nunused > 0;
 
+	/*
+	 * Even if we don't prune anything, if we found a new value for the
+	 * pd_prune_xid field or the page was marked full, we will update the hint
+	 * bit.
+	 */
+	do_hint_prune = ((PageHeader) page)->pd_prune_xid != prstate.new_prune_xid ||
+		PageIsFull(page);
+
 	/*
 	 * After processing all the live tuples on the page, if the newest xmin
 	 * amongst them is not visible to everyone, the page cannot be
@@ -916,14 +970,6 @@ heap_page_prune_and_freeze(Relation relation, Buffer buffer,
 		!GlobalVisXidVisibleToAll(prstate.vistest, prstate.visibility_cutoff_xid))
 		prstate.all_visible = prstate.all_frozen = false;
 
-	/*
-	 * Even if we don't prune anything, if we found a new value for the
-	 * pd_prune_xid field or the page was marked full, we will update the hint
-	 * bit.
-	 */
-	do_hint_prune = ((PageHeader) page)->pd_prune_xid != prstate.new_prune_xid ||
-		PageIsFull(page);
-
 	/*
 	 * Decide if we want to go ahead with freezing according to the freeze
 	 * plans we prepared, or not.
@@ -951,8 +997,6 @@ heap_page_prune_and_freeze(Relation relation, Buffer buffer,
 	if (prstate.lpdead_items > 0)
 		prstate.all_visible = prstate.all_frozen = false;
 
-	Assert(!prstate.all_frozen || prstate.all_visible);
-
 	/*
 	 * Determine whether or not to set the page level PD_ALL_VISIBLE and the
 	 * visibility map bits based on information from the VM and from
@@ -968,12 +1012,12 @@ heap_page_prune_and_freeze(Relation relation, Buffer buffer,
 	 * As such, it is possible to only update the VM when PD_ALL_VISIBLE is
 	 * already set.
 	 */
-	do_set_pd_vis = false;
-	do_set_vm = false;
-	if ((options & HEAP_PAGE_PRUNE_UPDATE_VIS) != 0)
-		do_set_vm = heap_page_will_set_vis(relation,
-										   blockno, buffer, vmbuffer, blk_known_av,
-										   &prstate, &new_vmbits, &do_set_pd_vis);
+	do_set_vm = heap_page_will_set_vis(relation,
+									   blockno, buffer, vmbuffer, blk_known_av,
+									   reason, do_prune, do_freeze,
+									   &prstate, &new_vmbits, &do_set_pd_vis);
+
+	Assert(!prstate.all_frozen || prstate.all_visible);
 
 	/* Lock vmbuffer before entering a critical section */
 	if (do_set_vm)
@@ -1134,7 +1178,6 @@ heap_page_prune_and_freeze(Relation relation, Buffer buffer,
 		bool		debug_all_frozen;
 
 		Assert(prstate.lpdead_items == 0);
-		Assert(prstate.cutoffs);
 
 		if (!heap_page_is_all_visible(relation, buffer,
 									  prstate.vistest,
@@ -2299,8 +2342,8 @@ heap_log_freeze_plan(HeapTupleFreeze *tuples, int ntuples,
  * - Reaping: During vacuum phase III, items that are already LP_DEAD are
  *   marked as unused.
  *
- * - VM updates: After vacuum phases I and III, the heap page may be marked
- *   all-visible and all-frozen.
+ * - VM updates: After vacuum phases I and III and on-access, the heap page
+ *   may be marked all-visible and all-frozen.
  *
  * These changes all happen together, so we use a single WAL record for them
  * all.
diff --git a/src/backend/access/index/indexam.c b/src/backend/access/index/indexam.c
index 0492d92d23b..8d582a8eafd 100644
--- a/src/backend/access/index/indexam.c
+++ b/src/backend/access/index/indexam.c
@@ -289,6 +289,32 @@ index_beginscan(Relation heapRelation,
 	return scan;
 }
 
+/*
+ * Similar to index_beginscan(), but allows the caller to indicate whether the
+ * query modifies the underlying base relation. This is used when the caller
+ * wants to attempt marking pages in the base relation as all-visible in the
+ * visibility map during on-access pruning.
+ */
+IndexScanDesc
+index_beginscan_vmset(Relation heapRelation,
+					  Relation indexRelation,
+					  Snapshot snapshot,
+					  IndexScanInstrumentation *instrument,
+					  int nkeys, int norderbys, bool modifies_base_rel)
+{
+	IndexScanDesc scan;
+
+	scan = index_beginscan(heapRelation,
+						   indexRelation,
+						   snapshot,
+						   instrument,
+						   nkeys, norderbys);
+
+	scan->xs_heapfetch->modifies_base_rel = modifies_base_rel;
+
+	return scan;
+}
+
 /*
  * index_beginscan_bitmap - start a scan of an index with amgetbitmap
  *
@@ -620,6 +646,26 @@ index_beginscan_parallel(Relation heaprel, Relation indexrel,
 	return scan;
 }
 
+/*
+ * Parallel version of index_beginscan_vmset()
+ */
+IndexScanDesc
+index_beginscan_parallel_vmset(Relation heaprel, Relation indexrel,
+							   IndexScanInstrumentation *instrument,
+							   int nkeys, int norderbys,
+							   ParallelIndexScanDesc pscan,
+							   bool modifies_base_rel)
+{
+	IndexScanDesc scan;
+
+	scan = index_beginscan_parallel(heaprel, indexrel,
+									instrument,
+									nkeys, norderbys,
+									pscan);
+	scan->xs_heapfetch->modifies_base_rel = modifies_base_rel;
+	return scan;
+}
+
 /* ----------------
  * index_getnext_tid - get the next TID from a scan
  *
diff --git a/src/backend/access/table/tableam.c b/src/backend/access/table/tableam.c
index a56c5eceb14..67dbf99f5b5 100644
--- a/src/backend/access/table/tableam.c
+++ b/src/backend/access/table/tableam.c
@@ -49,6 +49,10 @@
 char	   *default_table_access_method = DEFAULT_TABLE_ACCESS_METHOD;
 bool		synchronize_seqscans = true;
 
+/* Helper for table_beginscan_parallel() and table_beginscan_parallel_vmset() */
+static TableScanDesc table_beginscan_parallel_common(Relation relation, ParallelTableScanDesc pscan,
+													 uint32 flags);
+
 
 /* ----------------------------------------------------------------------------
  * Slot functions.
@@ -162,12 +166,14 @@ table_parallelscan_initialize(Relation rel, ParallelTableScanDesc pscan,
 	}
 }
 
-TableScanDesc
-table_beginscan_parallel(Relation relation, ParallelTableScanDesc pscan)
+/*
+ * Common helper for table_beginscan_parallel() and table_beginscan_parallel_vmset()
+ */
+static TableScanDesc
+table_beginscan_parallel_common(Relation relation, ParallelTableScanDesc pscan,
+								uint32 flags)
 {
 	Snapshot	snapshot;
-	uint32		flags = SO_TYPE_SEQSCAN |
-		SO_ALLOW_STRAT | SO_ALLOW_SYNC | SO_ALLOW_PAGEMODE;
 
 	Assert(RelFileLocatorEquals(relation->rd_locator, pscan->phs_locator));
 
@@ -188,6 +194,31 @@ table_beginscan_parallel(Relation relation, ParallelTableScanDesc pscan)
 											pscan, flags);
 }
 
+TableScanDesc
+table_beginscan_parallel(Relation relation, ParallelTableScanDesc pscan)
+{
+	uint32		flags = SO_TYPE_SEQSCAN |
+		SO_ALLOW_STRAT | SO_ALLOW_SYNC | SO_ALLOW_PAGEMODE;
+
+	return table_beginscan_parallel_common(relation, pscan, flags);
+}
+
+/*
+ * Parallel version of table_beginscan_vmset()
+ */
+TableScanDesc
+table_beginscan_parallel_vmset(Relation relation, ParallelTableScanDesc pscan,
+							   bool modifies_rel)
+{
+	uint32		flags = SO_TYPE_SEQSCAN |
+		SO_ALLOW_STRAT | SO_ALLOW_SYNC | SO_ALLOW_PAGEMODE;
+
+	if (!modifies_rel)
+		flags |= SO_ALLOW_VM_SET;
+
+	return table_beginscan_parallel_common(relation, pscan, flags);
+}
+
 
 /* ----------------------------------------------------------------------------
  * Index scan related functions.
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 831c55ce787..15be318fd41 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -916,6 +916,10 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 					break;
 			}
 
+			/* If it has a rowmark, the relation is 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);
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index fdc65c2b42b..28a06dcd244 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -893,6 +893,8 @@ 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/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index bf24f3d7fe0..af6db9f7919 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -105,11 +105,16 @@ BitmapTableScanSetup(BitmapHeapScanState *node)
 	 */
 	if (!node->ss.ss_currentScanDesc)
 	{
+		bool		modifies_rel =
+			bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+						  node->ss.ps.state->es_modified_relids);
+
 		node->ss.ss_currentScanDesc =
 			table_beginscan_bm(node->ss.ss_currentRelation,
 							   node->ss.ps.state->es_snapshot,
 							   0,
-							   NULL);
+							   NULL,
+							   modifies_rel);
 	}
 
 	node->ss.ss_currentScanDesc->st.rs_tbmiterator = tbmiterator;
diff --git a/src/backend/executor/nodeIndexscan.c b/src/backend/executor/nodeIndexscan.c
index 7fcaa37fe62..c2ffbd3b08e 100644
--- a/src/backend/executor/nodeIndexscan.c
+++ b/src/backend/executor/nodeIndexscan.c
@@ -102,16 +102,22 @@ IndexNext(IndexScanState *node)
 
 	if (scandesc == NULL)
 	{
+
+		bool		modifies_base_rel =
+			bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+						  estate->es_modified_relids);
+
 		/*
 		 * 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.
 		 */
-		scandesc = index_beginscan(node->ss.ss_currentRelation,
-								   node->iss_RelationDesc,
-								   estate->es_snapshot,
-								   &node->iss_Instrument,
-								   node->iss_NumScanKeys,
-								   node->iss_NumOrderByKeys);
+		scandesc = index_beginscan_vmset(node->ss.ss_currentRelation,
+										 node->iss_RelationDesc,
+										 estate->es_snapshot,
+										 &node->iss_Instrument,
+										 node->iss_NumScanKeys,
+										 node->iss_NumOrderByKeys,
+										 modifies_base_rel);
 
 		node->iss_ScanDesc = scandesc;
 
diff --git a/src/backend/executor/nodeSeqscan.c b/src/backend/executor/nodeSeqscan.c
index 94047d29430..fd69275c181 100644
--- a/src/backend/executor/nodeSeqscan.c
+++ b/src/backend/executor/nodeSeqscan.c
@@ -65,13 +65,18 @@ SeqNext(SeqScanState *node)
 
 	if (scandesc == NULL)
 	{
+		bool		modifies_rel =
+			bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+						  estate->es_modified_relids);
+
 		/*
 		 * 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);
+		scandesc = table_beginscan_vmset(node->ss.ss_currentRelation,
+										 estate->es_snapshot,
+										 0, NULL, modifies_rel);
+
 		node->ss.ss_currentScanDesc = scandesc;
 	}
 
@@ -366,6 +371,7 @@ ExecSeqScanInitializeDSM(SeqScanState *node,
 						 ParallelContext *pcxt)
 {
 	EState	   *estate = node->ss.ps.state;
+	bool		modifies_rel;
 	ParallelTableScanDesc pscan;
 
 	pscan = shm_toc_allocate(pcxt->toc, node->pscan_len);
@@ -373,8 +379,11 @@ ExecSeqScanInitializeDSM(SeqScanState *node,
 								  pscan,
 								  estate->es_snapshot);
 	shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, pscan);
+	modifies_rel = bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+								 estate->es_modified_relids);
 	node->ss.ss_currentScanDesc =
-		table_beginscan_parallel(node->ss.ss_currentRelation, pscan);
+		table_beginscan_parallel_vmset(node->ss.ss_currentRelation, pscan,
+									   modifies_rel);
 }
 
 /* ----------------------------------------------------------------
@@ -404,8 +413,13 @@ ExecSeqScanInitializeWorker(SeqScanState *node,
 							ParallelWorkerContext *pwcxt)
 {
 	ParallelTableScanDesc pscan;
+	bool		modifies_rel =
+		bms_is_member(((Scan *) node->ss.ps.plan)->scanrelid,
+					  node->ss.ps.state->es_modified_relids);
 
 	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);
+		table_beginscan_parallel_vmset(node->ss.ss_currentRelation,
+									   pscan,
+									   modifies_rel);
 }
diff --git a/src/include/access/genam.h b/src/include/access/genam.h
index 0831c33b038..87827127d96 100644
--- a/src/include/access/genam.h
+++ b/src/include/access/genam.h
@@ -174,6 +174,11 @@ extern IndexScanDesc index_beginscan(Relation heapRelation,
 									 Snapshot snapshot,
 									 IndexScanInstrumentation *instrument,
 									 int nkeys, int norderbys);
+extern IndexScanDesc index_beginscan_vmset(Relation heapRelation,
+										   Relation indexRelation,
+										   Snapshot snapshot,
+										   IndexScanInstrumentation *instrument,
+										   int nkeys, int norderbys, bool modifies_heap_rel);
 extern IndexScanDesc index_beginscan_bitmap(Relation indexRelation,
 											Snapshot snapshot,
 											IndexScanInstrumentation *instrument,
@@ -200,6 +205,12 @@ extern IndexScanDesc index_beginscan_parallel(Relation heaprel,
 											  IndexScanInstrumentation *instrument,
 											  int nkeys, int norderbys,
 											  ParallelIndexScanDesc pscan);
+
+extern IndexScanDesc index_beginscan_parallel_vmset(Relation heaprel, Relation indexrel,
+													IndexScanInstrumentation *instrument,
+													int nkeys, int norderbys,
+													ParallelIndexScanDesc pscan,
+													bool modifies_rel);
 extern ItemPointer index_getnext_tid(IndexScanDesc scan,
 									 ScanDirection direction);
 struct TupleTableSlot;
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 34ee323a423..9dcf8d29496 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -94,6 +94,13 @@ typedef struct HeapScanDescData
 	 */
 	ParallelBlockTableScanWorkerData *rs_parallelworkerdata;
 
+	/*
+	 * For sequential scans and bitmap heap scans. If the relation is not
+	 * being modified, on-access pruning may read in the current heap page's
+	 * corresponding VM block to this buffer.
+	 */
+	Buffer		rs_vmbuffer;
+
 	/* these fields only used in page-at-a-time mode and for bitmap scans */
 	uint32		rs_cindex;		/* current tuple's index in vistuples */
 	uint32		rs_ntuples;		/* number of visible tuples on page */
@@ -116,8 +123,18 @@ typedef struct IndexFetchHeapData
 {
 	IndexFetchTableData xs_base;	/* AM independent part of the descriptor */
 
-	Buffer		xs_cbuf;		/* current heap buffer in scan, if any */
-	/* NB: if xs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
+	/*
+	 * Current heap buffer in scan, if any. NB: if xs_cbuf is not
+	 * InvalidBuffer, we hold a pin on that buffer.
+	 */
+	Buffer		xs_cbuf;
+
+	/*
+	 * For index scans that do not modify the underlying heap table, on-access
+	 * pruning may read in the current heap page's corresponding VM block to
+	 * this buffer.
+	 */
+	Buffer		xs_vmbuffer;
 } IndexFetchHeapData;
 
 /* Result codes for HeapTupleSatisfiesVacuum */
@@ -363,7 +380,8 @@ extern TransactionId heap_index_delete_tuples(Relation rel,
 
 /* in heap/pruneheap.c */
 struct GlobalVisState;
-extern void heap_page_prune_opt(Relation relation, Buffer buffer);
+extern void heap_page_prune_opt(Relation relation, Buffer buffer,
+								Buffer *vmbuffer);
 extern void heap_page_prune_and_freeze(Relation relation, Buffer buffer,
 									   Buffer vmbuffer, bool blk_known_av,
 									   PruneReason reason,
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index b5e0fb386c0..f496e0b4939 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -121,6 +121,12 @@ typedef struct ParallelBlockTableScanWorkerData *ParallelBlockTableScanWorker;
 typedef struct IndexFetchTableData
 {
 	Relation	rel;
+
+	/*
+	 * Some optimizations can only be performed if the query does not modify
+	 * the underlying relation. Track that here.
+	 */
+	bool		modifies_base_rel;
 } IndexFetchTableData;
 
 struct IndexScanInstrumentation;
diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
index 77eb41eb6dc..6f5d4f9bb65 100644
--- a/src/include/access/tableam.h
+++ b/src/include/access/tableam.h
@@ -62,6 +62,8 @@ typedef enum ScanOptions
 
 	/* unregister snapshot at scan end? */
 	SO_TEMP_SNAPSHOT = 1 << 9,
+	/* whether or not scan should attempt to set the VM */
+	SO_ALLOW_VM_SET = 1 << 10,
 }			ScanOptions;
 
 /*
@@ -881,6 +883,25 @@ table_beginscan(Relation rel, Snapshot snapshot,
 	return rel->rd_tableam->scan_begin(rel, snapshot, nkeys, key, NULL, flags);
 }
 
+/*
+ * Similar to table_beginscan(), but allows the caller to indicate whether the
+ * query modifies the relation. This is used when the caller wants to attempt
+ * marking pages in the relation as all-visible in the visibility map during
+ * on-access pruning.
+ */
+static inline TableScanDesc
+table_beginscan_vmset(Relation rel, Snapshot snapshot,
+					  int nkeys, struct ScanKeyData *key, bool modifies_rel)
+{
+	uint32		flags = SO_TYPE_SEQSCAN |
+		SO_ALLOW_STRAT | SO_ALLOW_SYNC | SO_ALLOW_PAGEMODE;
+
+	if (!modifies_rel)
+		flags |= SO_ALLOW_VM_SET;
+
+	return rel->rd_tableam->scan_begin(rel, snapshot, nkeys, key, NULL, flags);
+}
+
 /*
  * Like table_beginscan(), but for scanning catalog. It'll automatically use a
  * snapshot appropriate for scanning catalog relations.
@@ -918,10 +939,13 @@ table_beginscan_strat(Relation rel, Snapshot snapshot,
  */
 static inline TableScanDesc
 table_beginscan_bm(Relation rel, Snapshot snapshot,
-				   int nkeys, struct ScanKeyData *key)
+				   int nkeys, struct ScanKeyData *key, bool modifies_rel)
 {
 	uint32		flags = SO_TYPE_BITMAPSCAN | SO_ALLOW_PAGEMODE;
 
+	if (!modifies_rel)
+		flags |= SO_ALLOW_VM_SET;
+
 	return rel->rd_tableam->scan_begin(rel, snapshot, nkeys, key,
 									   NULL, flags);
 }
@@ -1130,6 +1154,10 @@ extern void table_parallelscan_initialize(Relation rel,
 extern TableScanDesc table_beginscan_parallel(Relation relation,
 											  ParallelTableScanDesc pscan);
 
+extern TableScanDesc table_beginscan_parallel_vmset(Relation relation,
+													ParallelTableScanDesc pscan,
+													bool modifies_rel);
+
 /*
  * Restart a parallel scan.  Call this in the leader process.  Caller is
  * responsible for making sure that all workers have finished the scan
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 3a920cc7d17..c854be93436 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -676,6 +676,12 @@ typedef struct EState
 									 * ExecDoInitialPruning() */
 	const char *es_sourceText;	/* Source text from QueryDesc */
 
+	/*
+	 * RT indexes of relations modified by the query either through
+	 * UPDATE/DELETE/INSERT/MERGE or 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 */
diff --git a/src/test/recovery/t/035_standby_logical_decoding.pl b/src/test/recovery/t/035_standby_logical_decoding.pl
index c9c182892cf..f5c0c65b260 100644
--- a/src/test/recovery/t/035_standby_logical_decoding.pl
+++ b/src/test/recovery/t/035_standby_logical_decoding.pl
@@ -296,6 +296,7 @@ wal_level = 'logical'
 max_replication_slots = 4
 max_wal_senders = 4
 autovacuum = off
+hot_standby_feedback = on
 });
 $node_primary->dump_info;
 $node_primary->start;
@@ -745,7 +746,7 @@ check_pg_recvlogical_stderr($handle,
 $logstart = -s $node_standby->logfile;
 
 reactive_slots_change_hfs_and_wait_for_xmins('shared_row_removal_',
-	'no_conflict_', 0, 1);
+	'no_conflict_', 1, 0);
 
 # This should not trigger a conflict
 wait_until_vacuum_can_remove(
-- 
2.43.0