From: Tomas Vondra <tomas.vondra@postgresql.org>
Date: Sat, 6 Apr 2024 21:56:46 +0000 (+0200)
Subject: BitmapHeapScan: postpone setting can_skip_fetch
X-Git-Tag: REL_17_BETA1~370
X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=fe1431e39cdde5f65cb52f068bc86a7490f8a4e3;p=postgresql.git

BitmapHeapScan: postpone setting can_skip_fetch

Set BitmapHeapScanState->can_skip_fetch in BitmapHeapNext() instead of
in ExecInitBitmapHeapScan(). This is a preliminary step to pushing the
skip fetch optimization into heap AM code.

Author: Melanie Plageman
Reviewed-by: Tomas Vondra, Andres Freund, Heikki Linnakangas
Discussion: https://postgr.es/m/CAAKRu_ZwCwWFeL_H3ia26bP2e7HiKLWt0ZmGXPVwPO6uXq0vaA%40mail.gmail.com
---

diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index c8c466e3c5c..2148a21531a 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -105,6 +105,16 @@ BitmapHeapNext(BitmapHeapScanState *node)
 	 */
 	if (!node->initialized)
 	{
+		/*
+		 * We can potentially skip fetching heap pages if we do not need any
+		 * columns of the table, either for checking non-indexable quals or
+		 * for returning data.  This test is a bit simplistic, as it checks
+		 * the stronger condition that there's no qual or return tlist at all.
+		 * But in most cases it's probably not worth working harder than that.
+		 */
+		node->can_skip_fetch = (node->ss.ps.plan->qual == NIL &&
+								node->ss.ps.plan->targetlist == NIL);
+
 		if (!pstate)
 		{
 			tbm = (TIDBitmap *) MultiExecProcNode(outerPlanState(node));
@@ -743,16 +753,7 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
 	scanstate->shared_tbmiterator = NULL;
 	scanstate->shared_prefetch_iterator = NULL;
 	scanstate->pstate = NULL;
-
-	/*
-	 * We can potentially skip fetching heap pages if we do not need any
-	 * columns of the table, either for checking non-indexable quals or for
-	 * returning data.  This test is a bit simplistic, as it checks the
-	 * stronger condition that there's no qual or return tlist at all.  But in
-	 * most cases it's probably not worth working harder than that.
-	 */
-	scanstate->can_skip_fetch = (node->scan.plan.qual == NIL &&
-								 node->scan.plan.targetlist == NIL);
+	scanstate->can_skip_fetch = false;
 
 	/*
 	 * Miscellaneous initialization