v1-0002-Simplify-vacuum-VM-update-logging-counters.patch

From 6cbbdd359ae4de835bbd77369b598885e8a279b2 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Wed, 18 Jun 2025 16:12:15 -0400
Subject: [PATCH v1 02/14] Simplify vacuum VM update logging counters

We can simplify the VM counters added in dc6acfd910b8 to
lazy_vacuum_heap_page() and lazy_scan_new_or_empty().

We won't invoke lazy_vacuum_heap_page() unless there are dead line
pointers, so we know the page can't be all-visible.

In lazy_scan_new_or_empty(), we only update the VM if the page-level
hint PD_ALL_VISIBLE is clear, and the VM bit cannot be set if the page
level bit is clear because a subsequent page update would fail to clear
the visibility map bit.

Simplify the logic for determining which log counters to increment based
on this knowledge.
---
 src/backend/access/heap/vacuumlazy.c | 32 +++++++++++-----------------
 1 file changed, 12 insertions(+), 20 deletions(-)

diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index 09416450af9..c8da2f835c4 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -1900,17 +1900,12 @@ lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, BlockNumber blkno,
 										   VISIBILITYMAP_ALL_FROZEN);
 			END_CRIT_SECTION();
 
-			/*
-			 * If the page wasn't already set all-visible and/or all-frozen in
-			 * the VM, count it as newly set for logging.
-			 */
-			if ((old_vmbits & VISIBILITYMAP_ALL_VISIBLE) == 0)
-			{
-				vacrel->vm_new_visible_pages++;
-				vacrel->vm_new_visible_frozen_pages++;
-			}
-			else if ((old_vmbits & VISIBILITYMAP_ALL_FROZEN) == 0)
-				vacrel->vm_new_frozen_pages++;
+			/* VM bits cannot have been set if PD_ALL_VISIBLE was clear */
+			Assert((old_vmbits & VISIBILITYMAP_VALID_BITS) == 0);
+			(void) old_vmbits; /* Silence compiler */
+			/* Count the newly all-frozen pages for logging. */
+			vacrel->vm_new_visible_pages++;
+			vacrel->vm_new_visible_frozen_pages++;
 		}
 
 		freespace = PageGetHeapFreeSpace(page);
@@ -2930,20 +2925,17 @@ lazy_vacuum_heap_page(LVRelState *vacrel, BlockNumber blkno, Buffer buffer,
 									   vmbuffer, visibility_cutoff_xid,
 									   flags);
 
-		/*
-		 * If the page wasn't already set all-visible and/or all-frozen in the
-		 * VM, count it as newly set for logging.
-		 */
-		if ((old_vmbits & VISIBILITYMAP_ALL_VISIBLE) == 0)
+		/* We know the page should not have been all-visible */
+		Assert((old_vmbits & VISIBILITYMAP_VALID_BITS) == 0);
+		(void) old_vmbits; /* Silence compiler */
+
+		/* Count the newly set VM page for logging */
+		if ((flags & VISIBILITYMAP_ALL_VISIBLE) != 0)
 		{
 			vacrel->vm_new_visible_pages++;
 			if (all_frozen)
 				vacrel->vm_new_visible_frozen_pages++;
 		}
-
-		else if ((old_vmbits & VISIBILITYMAP_ALL_FROZEN) == 0 &&
-				 all_frozen)
-			vacrel->vm_new_frozen_pages++;
 	}
 
 	/* Revert to the previous phase information for error traceback */
-- 
2.34.1