From 62f6c877d130325748bf18724fc8166932605091 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Mon, 12 Feb 2024 18:50:29 -0500
Subject: [PATCH v10 01/17] BitmapHeapScan begin scan after bitmap creation

There is no reason for a BitmapHeapScan to begin the scan of the
underlying table in ExecInitBitmapHeapScan(). Instead, do so after
completing the index scan and building the bitmap.
---
 src/backend/access/table/tableam.c        |  1 -
 src/backend/executor/nodeBitmapHeapscan.c | 26 +++++++++++++++++------
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/src/backend/access/table/tableam.c b/src/backend/access/table/tableam.c
index e57a0b7ea3..e78d793f69 100644
--- a/src/backend/access/table/tableam.c
+++ b/src/backend/access/table/tableam.c
@@ -120,7 +120,6 @@ table_beginscan_catalog(Relation relation, int nkeys, struct ScanKeyData *key)
 											NULL, flags);
 }
 
-
 /* ----------------------------------------------------------------------------
  * Parallel table scan related functions.
  * ----------------------------------------------------------------------------
diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index cee7f45aab..93fdcd226b 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -178,6 +178,20 @@ BitmapHeapNext(BitmapHeapScanState *node)
 			}
 #endif							/* USE_PREFETCH */
 		}
+
+		/*
+		 * If this is the first scan of the underlying table, create the table
+		 * scan descriptor and begin the scan.
+		 */
+		if (!scan)
+		{
+			scan = node->ss.ss_currentScanDesc = table_beginscan_bm(
+																	node->ss.ss_currentRelation,
+																	node->ss.ps.state->es_snapshot,
+																	0,
+																	NULL);
+		}
+
 		node->initialized = true;
 	}
 
@@ -601,7 +615,8 @@ ExecReScanBitmapHeapScan(BitmapHeapScanState *node)
 	PlanState  *outerPlan = outerPlanState(node);
 
 	/* rescan to release any page pin */
-	table_rescan(node->ss.ss_currentScanDesc, NULL);
+	if (node->ss.ss_currentScanDesc)
+		table_rescan(node->ss.ss_currentScanDesc, NULL);
 
 	/* release bitmaps and buffers if any */
 	if (node->tbmiterator)
@@ -678,7 +693,9 @@ ExecEndBitmapHeapScan(BitmapHeapScanState *node)
 	/*
 	 * close heap scan
 	 */
-	table_endscan(scanDesc);
+	if (scanDesc)
+		table_endscan(scanDesc);
+
 }
 
 /* ----------------------------------------------------------------
@@ -783,11 +800,6 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
 
 	scanstate->ss.ss_currentRelation = currentRelation;
 
-	scanstate->ss.ss_currentScanDesc = table_beginscan_bm(currentRelation,
-														  estate->es_snapshot,
-														  0,
-														  NULL);
-
 	/*
 	 * all done.
 	 */
-- 
2.40.1