From 8f47b1e0163028ec8928aaf02ce49d34bb89c647 Mon Sep 17 00:00:00 2001
From: David Rowley <dgrowley@gmail.com>
Date: Wed, 19 Oct 2022 08:55:45 +1300
Subject: [PATCH v2 4/5] heapam: WIP: cacheline prefetching for hot pruning.

Author: Andres Freund, with contributions from Dmitry Dolgov
---
 src/backend/access/heap/pruneheap.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/src/backend/access/heap/pruneheap.c b/src/backend/access/heap/pruneheap.c
index 91c5f5e9ef..a094ac18f5 100644
--- a/src/backend/access/heap/pruneheap.c
+++ b/src/backend/access/heap/pruneheap.c
@@ -302,6 +302,30 @@ heap_page_prune(Relation relation, Buffer buffer,
 	maxoff = PageGetMaxOffsetNumber(page);
 	tup.t_tableOid = RelationGetRelid(prstate.rel);
 
+#if 1
+	for (char *p = (char *) PageGetItemId(page, FirstOffsetNumber);
+		 p < (char *) PageGetItemId(page, maxoff);
+		 p += 64)
+	{
+		pg_prefetch_mem((ItemId)p);
+	}
+
+
+	for (offnum = FirstOffsetNumber;
+		 offnum <= maxoff;
+		 offnum = OffsetNumberNext(offnum))
+	{
+		ItemId		itemid;
+
+		itemid = PageGetItemId(page, offnum);
+		if (!ItemIdIsUsed(itemid) || ItemIdIsDead(itemid) || !ItemIdHasStorage(itemid))
+			continue;
+
+		pg_prefetch_mem((HeapTupleHeader) PageGetItem(page, itemid));
+		pg_prefetch_mem(PageGetItem(page, itemid) + sizeof(HeapTupleHeaderData) - 1);
+	}
+#endif
+
 	/*
 	 * Determine HTSV for all tuples.
 	 *
-- 
2.35.1.windows.2