v18-0002-Keep-all_frozen-updated-in-heap_page_prune_and_f.patch

From 4c3f113fbd62b553949b95cb352347767278e7dc Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Tue, 14 Oct 2025 14:55:40 -0400
Subject: [PATCH v18 02/12] Keep all_frozen updated in
 heap_page_prune_and_freeze

Previously, we relied on all_visible and all_frozen being used together
to ensure that all_frozen was correct, but it is better to keep both
fields updated.

Future changes will separate their usage, so we should not depend on
all_visible for the validity of all_frozen.
---
 src/backend/access/heap/pruneheap.c  | 22 +++++++++++-----------
 src/backend/access/heap/vacuumlazy.c |  9 ++++-----
 2 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/src/backend/access/heap/pruneheap.c b/src/backend/access/heap/pruneheap.c
index 450b2eb6494..daa719fc2a1 100644
--- a/src/backend/access/heap/pruneheap.c
+++ b/src/backend/access/heap/pruneheap.c
@@ -143,10 +143,6 @@ typedef struct
 	 * whether to freeze the page or not.  The all_visible and all_frozen
 	 * values returned to the caller are adjusted to include LP_DEAD items at
 	 * the end.
-	 *
-	 * all_frozen should only be considered valid if all_visible is also set;
-	 * we don't bother to clear the all_frozen flag every time we clear the
-	 * all_visible flag.
 	 */
 	bool		all_visible;
 	bool		all_frozen;
@@ -361,8 +357,10 @@ heap_page_will_freeze(Relation relation, Buffer buffer,
 		 * anymore.  The opportunistic freeze heuristic must be improved;
 		 * however, for now, try to approximate the old logic.
 		 */
-		if (prstate->all_visible && prstate->all_frozen && prstate->nfrozen > 0)
+		if (prstate->all_frozen && prstate->nfrozen > 0)
 		{
+			Assert(prstate->all_visible);
+
 			/*
 			 * Freezing would make the page all-frozen.  Have already emitted
 			 * an FPI or will do so anyway?
@@ -784,6 +782,8 @@ heap_page_prune_and_freeze(PruneFreezeParams *params,
 									  do_hint_prune,
 									  &prstate);
 
+	Assert(!prstate.all_frozen || prstate.all_visible);
+
 	/* Any error while applying the changes is critical */
 	START_CRIT_SECTION();
 
@@ -853,7 +853,7 @@ heap_page_prune_and_freeze(PruneFreezeParams *params,
 			 */
 			if (do_freeze)
 			{
-				if (prstate.all_visible && prstate.all_frozen)
+				if (prstate.all_frozen)
 					frz_conflict_horizon = prstate.visibility_cutoff_xid;
 				else
 				{
@@ -1418,7 +1418,7 @@ heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumb
 
 				if (!HeapTupleHeaderXminCommitted(htup))
 				{
-					prstate->all_visible = false;
+					prstate->all_visible = prstate->all_frozen = false;
 					break;
 				}
 
@@ -1440,7 +1440,7 @@ heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumb
 				Assert(prstate->cutoffs);
 				if (!TransactionIdPrecedes(xmin, prstate->cutoffs->OldestXmin))
 				{
-					prstate->all_visible = false;
+					prstate->all_visible = prstate->all_frozen = false;
 					break;
 				}
 
@@ -1453,7 +1453,7 @@ heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumb
 
 		case HEAPTUPLE_RECENTLY_DEAD:
 			prstate->recently_dead_tuples++;
-			prstate->all_visible = false;
+			prstate->all_visible = prstate->all_frozen = false;
 
 			/*
 			 * This tuple will soon become DEAD.  Update the hint field so
@@ -1472,7 +1472,7 @@ heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumb
 			 * assumption is a bit shaky, but it is what acquire_sample_rows()
 			 * does, so be consistent.
 			 */
-			prstate->all_visible = false;
+			prstate->all_visible = prstate->all_frozen = false;
 
 			/*
 			 * If we wanted to optimize for aborts, we might consider marking
@@ -1490,7 +1490,7 @@ heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumb
 			 * will commit and update the counters after we report.
 			 */
 			prstate->live_tuples++;
-			prstate->all_visible = false;
+			prstate->all_visible = prstate->all_frozen = false;
 
 			/*
 			 * This tuple may soon become DEAD.  Update the hint field so that
diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index 7db7c56311b..58de605ca09 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -2020,7 +2020,6 @@ lazy_scan_prune(LVRelState *vacrel,
 	 * agreement with heap_page_is_all_visible() using an assertion.
 	 */
 #ifdef USE_ASSERT_CHECKING
-	/* Note that all_frozen value does not matter when !all_visible */
 	if (presult.all_visible)
 	{
 		TransactionId debug_cutoff;
@@ -2074,6 +2073,7 @@ lazy_scan_prune(LVRelState *vacrel,
 	*has_lpdead_items = (presult.lpdead_items > 0);
 
 	Assert(!presult.all_visible || !(*has_lpdead_items));
+	Assert(!presult.all_frozen || presult.all_visible);
 
 	/*
 	 * Handle setting visibility map bit based on information from the VM (as
@@ -2179,11 +2179,10 @@ lazy_scan_prune(LVRelState *vacrel,
 
 	/*
 	 * If the all-visible page is all-frozen but not marked as such yet, mark
-	 * it as all-frozen.  Note that all_frozen is only valid if all_visible is
-	 * true, so we must check both all_visible and all_frozen.
+	 * it as all-frozen.
 	 */
-	else if (all_visible_according_to_vm && presult.all_visible &&
-			 presult.all_frozen && !VM_ALL_FROZEN(vacrel->rel, blkno, &vmbuffer))
+	else if (all_visible_according_to_vm && presult.all_frozen &&
+			 !VM_ALL_FROZEN(vacrel->rel, blkno, &vmbuffer))
 	{
 		uint8		old_vmbits;
 
-- 
2.43.0