Thread

[PATCH 1/6] Pass the number of ScanKeys to scan_rescan()

Julien Tachoires <julien@tachoires.me> — 2025-08-25T15:01:57Z

The number of ScanKeys passed to the table AM API routine scan_rescan()
was not specified, forcing the table AM to keep in memory the initial
number of ScanKeys passed via scan_begin(). Currenlty, there isn't any
real use of the ScanKeys during a table scan, so, this is not an issue,
but it could become a blocking point in the future if we want to
implement quals push down - as ScanKeys - to the table AM. Due to
runtime keys evaluation, this number of ScanKeys can vary between the
initial call to scan_begin() and a potential further call
to scan_rescan().

table_rescan() is modified in order to reflect the changes on
scan_rescan().

table_beginscan_parallel() signature is slightly modified in order to
pass eventual ScanKeys and their numbers to scan_begin().

table_rescan_set_params() now takes the number of ScanKeys as a new
argument.
---
 src/backend/access/brin/brin.c            |  3 ++-
 src/backend/access/gin/gininsert.c        |  3 ++-
 src/backend/access/heap/heapam.c          |  2 +-
 src/backend/access/nbtree/nbtsort.c       |  3 ++-
 src/backend/access/table/tableam.c        |  5 +++--
 src/backend/executor/execReplication.c    |  4 ++--
 src/backend/executor/nodeBitmapHeapscan.c |  2 +-
 src/backend/executor/nodeSamplescan.c     |  2 +-
 src/backend/executor/nodeSeqscan.c        |  5 +++--
 src/backend/executor/nodeTidscan.c        |  2 +-
 src/include/access/heapam.h               |  5 +++--
 src/include/access/tableam.h              | 24 +++++++++++++----------
 12 files changed, 35 insertions(+), 25 deletions(-)

diff --git a/src/backend/access/brin/brin.c b/src/backend/access/brin/brin.c
index 7ff7467e462..5995bd1243e 100644
--- a/src/backend/access/brin/brin.c
+++ b/src/backend/access/brin/brin.c
@@ -2828,7 +2828,8 @@ _brin_parallel_scan_and_build(BrinBuildState *state,
 	indexInfo->ii_Concurrent = brinshared->isconcurrent;
 
 	scan = table_beginscan_parallel(heap,
-									ParallelTableScanFromBrinShared(brinshared));
+									ParallelTableScanFromBrinShared(brinshared),
+									0, NULL);
 
 	reltuples = table_index_build_scan(heap, index, indexInfo, true, true,
 									   brinbuildCallbackParallel, state, scan);
diff --git a/src/backend/access/gin/gininsert.c b/src/backend/access/gin/gininsert.c
index e9d4b27427e..deaa42cffa4 100644
--- a/src/backend/access/gin/gininsert.c
+++ b/src/backend/access/gin/gininsert.c
@@ -2030,7 +2030,8 @@ _gin_parallel_scan_and_build(GinBuildState *state,
 	indexInfo->ii_Concurrent = ginshared->isconcurrent;
 
 	scan = table_beginscan_parallel(heap,
-									ParallelTableScanFromGinBuildShared(ginshared));
+									ParallelTableScanFromGinBuildShared(ginshared),
+									0, NULL);
 
 	reltuples = table_index_build_scan(heap, index, indexInfo, true, progress,
 									   ginBuildCallbackParallel, state, scan);
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 7491cc3cb93..a5c74d8948e 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -1251,7 +1251,7 @@ heap_beginscan(Relation relation, Snapshot snapshot,
 }
 
 void
-heap_rescan(TableScanDesc sscan, ScanKey key, bool set_params,
+heap_rescan(TableScanDesc sscan, int nkeys, ScanKey key, bool set_params,
 			bool allow_strat, bool allow_sync, bool allow_pagemode)
 {
 	HeapScanDesc scan = (HeapScanDesc) sscan;
diff --git a/src/backend/access/nbtree/nbtsort.c b/src/backend/access/nbtree/nbtsort.c
index 8828a7a8f89..d576ba3a762 100644
--- a/src/backend/access/nbtree/nbtsort.c
+++ b/src/backend/access/nbtree/nbtsort.c
@@ -1927,7 +1927,8 @@ _bt_parallel_scan_and_sort(BTSpool *btspool, BTSpool *btspool2,
 	indexInfo = BuildIndexInfo(btspool->index);
 	indexInfo->ii_Concurrent = btshared->isconcurrent;
 	scan = table_beginscan_parallel(btspool->heap,
-									ParallelTableScanFromBTShared(btshared));
+									ParallelTableScanFromBTShared(btshared),
+									0, NULL);
 	reltuples = table_index_build_scan(btspool->heap, btspool->index, indexInfo,
 									   true, progress, _bt_build_callback,
 									   &buildstate, scan);
diff --git a/src/backend/access/table/tableam.c b/src/backend/access/table/tableam.c
index a56c5eceb14..46bed1614f0 100644
--- a/src/backend/access/table/tableam.c
+++ b/src/backend/access/table/tableam.c
@@ -163,7 +163,8 @@ table_parallelscan_initialize(Relation rel, ParallelTableScanDesc pscan,
 }
 
 TableScanDesc
-table_beginscan_parallel(Relation relation, ParallelTableScanDesc pscan)
+table_beginscan_parallel(Relation relation, ParallelTableScanDesc pscan,
+						 int nkeys, struct ScanKeyData *key)
 {
 	Snapshot	snapshot;
 	uint32		flags = SO_TYPE_SEQSCAN |
@@ -184,7 +185,7 @@ table_beginscan_parallel(Relation relation, ParallelTableScanDesc pscan)
 		snapshot = SnapshotAny;
 	}
 
-	return relation->rd_tableam->scan_begin(relation, snapshot, 0, NULL,
+	return relation->rd_tableam->scan_begin(relation, snapshot, nkeys, key,
 											pscan, flags);
 }
 
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index b409d4ecbf5..1b0c97243a5 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -388,7 +388,7 @@ RelationFindReplTupleSeq(Relation rel, LockTupleMode lockmode,
 retry:
 	found = false;
 
-	table_rescan(scan, NULL);
+	table_rescan(scan, 0, NULL);
 
 	/* Try to find the tuple */
 	while (table_scan_getnextslot(scan, ForwardScanDirection, scanslot))
@@ -604,7 +604,7 @@ RelationFindDeletedTupleInfoSeq(Relation rel, TupleTableSlot *searchslot,
 	scan = table_beginscan(rel, SnapshotAny, 0, NULL);
 	scanslot = table_slot_create(rel, NULL);
 
-	table_rescan(scan, NULL);
+	table_rescan(scan, 0, NULL);
 
 	/* Try to find the tuple */
 	while (table_scan_getnextslot(scan, ForwardScanDirection, scanslot))
diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index bf24f3d7fe0..fb778e0ae3b 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -239,7 +239,7 @@ ExecReScanBitmapHeapScan(BitmapHeapScanState *node)
 			tbm_end_iterate(&scan->st.rs_tbmiterator);
 
 		/* rescan to release any page pin */
-		table_rescan(node->ss.ss_currentScanDesc, NULL);
+		table_rescan(node->ss.ss_currentScanDesc, 0, NULL);
 	}
 
 	/* release bitmaps and buffers if any */
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
index 6b3db7548ed..a7e172d83a4 100644
--- a/src/backend/executor/nodeSamplescan.c
+++ b/src/backend/executor/nodeSamplescan.c
@@ -301,7 +301,7 @@ tablesample_init(SampleScanState *scanstate)
 	}
 	else
 	{
-		table_rescan_set_params(scanstate->ss.ss_currentScanDesc, NULL,
+		table_rescan_set_params(scanstate->ss.ss_currentScanDesc, 0, NULL,
 								scanstate->use_bulkread,
 								allow_sync,
 								scanstate->use_pagemode);
diff --git a/src/backend/executor/nodeSeqscan.c b/src/backend/executor/nodeSeqscan.c
index 94047d29430..c89aa6c6616 100644
--- a/src/backend/executor/nodeSeqscan.c
+++ b/src/backend/executor/nodeSeqscan.c
@@ -326,6 +326,7 @@ ExecReScanSeqScan(SeqScanState *node)
 
 	if (scan != NULL)
 		table_rescan(scan,		/* scan desc */
+					 0,			/* number of scan keys */
 					 NULL);		/* new scan keys */
 
 	ExecScanReScan((ScanState *) node);
@@ -374,7 +375,7 @@ ExecSeqScanInitializeDSM(SeqScanState *node,
 								  estate->es_snapshot);
 	shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, pscan);
 	node->ss.ss_currentScanDesc =
-		table_beginscan_parallel(node->ss.ss_currentRelation, pscan);
+		table_beginscan_parallel(node->ss.ss_currentRelation, pscan, 0, NULL);
 }
 
 /* ----------------------------------------------------------------
@@ -407,5 +408,5 @@ ExecSeqScanInitializeWorker(SeqScanState *node,
 
 	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(node->ss.ss_currentRelation, pscan, 0, NULL);
 }
diff --git a/src/backend/executor/nodeTidscan.c b/src/backend/executor/nodeTidscan.c
index 5e56e29a15f..6b37d1fcb74 100644
--- a/src/backend/executor/nodeTidscan.c
+++ b/src/backend/executor/nodeTidscan.c
@@ -454,7 +454,7 @@ ExecReScanTidScan(TidScanState *node)
 
 	/* not really necessary, but seems good form */
 	if (node->ss.ss_currentScanDesc)
-		table_rescan(node->ss.ss_currentScanDesc, NULL);
+		table_rescan(node->ss.ss_currentScanDesc, 0, NULL);
 
 	ExecScanReScan(&node->ss);
 }
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index a2bd5a897f8..252f5e661c1 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -293,8 +293,9 @@ extern TableScanDesc heap_beginscan(Relation relation, Snapshot snapshot,
 extern void heap_setscanlimits(TableScanDesc sscan, BlockNumber startBlk,
 							   BlockNumber numBlks);
 extern void heap_prepare_pagescan(TableScanDesc sscan);
-extern void heap_rescan(TableScanDesc sscan, ScanKey key, bool set_params,
-						bool allow_strat, bool allow_sync, bool allow_pagemode);
+extern void heap_rescan(TableScanDesc sscan, int nkeys, ScanKey key,
+						bool set_params, bool allow_strat, bool allow_sync,
+						bool allow_pagemode);
 extern void heap_endscan(TableScanDesc sscan);
 extern HeapTuple heap_getnext(TableScanDesc sscan, ScanDirection direction);
 extern bool heap_getnextslot(TableScanDesc sscan,
diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
index 1c9e802a6b1..6fa0fa55a33 100644
--- a/src/include/access/tableam.h
+++ b/src/include/access/tableam.h
@@ -334,9 +334,10 @@ typedef struct TableAmRoutine
 	 * Restart relation scan.  If set_params is set to true, allow_{strat,
 	 * sync, pagemode} (see scan_begin) changes should be taken into account.
 	 */
-	void		(*scan_rescan) (TableScanDesc scan, struct ScanKeyData *key,
-								bool set_params, bool allow_strat,
-								bool allow_sync, bool allow_pagemode);
+	void		(*scan_rescan) (TableScanDesc scan, int nkeys,
+								struct ScanKeyData *key, bool set_params,
+								bool allow_strat, bool allow_sync,
+								bool allow_pagemode);
 
 	/*
 	 * Return next tuple from `scan`, store in slot.
@@ -985,10 +986,10 @@ table_endscan(TableScanDesc scan)
  * Restart a relation scan.
  */
 static inline void
-table_rescan(TableScanDesc scan,
-			 struct ScanKeyData *key)
+table_rescan(TableScanDesc scan, int nkeys, struct ScanKeyData *key)
 {
-	scan->rs_rd->rd_tableam->scan_rescan(scan, key, false, false, false, false);
+	scan->rs_rd->rd_tableam->scan_rescan(scan, nkeys, key, false, false, false,
+										 false);
 }
 
 /*
@@ -1000,10 +1001,10 @@ table_rescan(TableScanDesc scan,
  * previously selected startblock will be kept.
  */
 static inline void
-table_rescan_set_params(TableScanDesc scan, struct ScanKeyData *key,
+table_rescan_set_params(TableScanDesc scan, int nkeys, struct ScanKeyData *key,
 						bool allow_strat, bool allow_sync, bool allow_pagemode)
 {
-	scan->rs_rd->rd_tableam->scan_rescan(scan, key, true,
+	scan->rs_rd->rd_tableam->scan_rescan(scan, nkeys, key, true,
 										 allow_strat, allow_sync,
 										 allow_pagemode);
 }
@@ -1068,7 +1069,8 @@ table_rescan_tidrange(TableScanDesc sscan, ItemPointer mintid,
 	/* Ensure table_beginscan_tidrange() was used. */
 	Assert((sscan->rs_flags & SO_TYPE_TIDRANGESCAN) != 0);
 
-	sscan->rs_rd->rd_tableam->scan_rescan(sscan, NULL, false, false, false, false);
+	sscan->rs_rd->rd_tableam->scan_rescan(sscan, 0, NULL, false, false, false,
+										  false);
 	sscan->rs_rd->rd_tableam->scan_set_tidrange(sscan, mintid, maxtid);
 }
 
@@ -1123,7 +1125,9 @@ extern void table_parallelscan_initialize(Relation rel,
  * Caller must hold a suitable lock on the relation.
  */
 extern TableScanDesc table_beginscan_parallel(Relation relation,
-											  ParallelTableScanDesc pscan);
+											  ParallelTableScanDesc pscan,
+											  int nkeys,
+											  struct ScanKeyData *key);
 
 /*
  * Restart a parallel scan.  Call this in the leader process.  Caller is
-- 
2.39.5


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