From f72a487d75f98d852a9da10b3fdd3db9aa2cbae4 Mon Sep 17 00:00:00 2001 From: Melanie Plageman Date: Fri, 25 Sep 2026 14:57:28 -0400 Subject: [PATCH v1 04/11] Repair visibility map corruption on empty pages lazy_scan_new_or_empty() only checked PD_ALL_VISIBLE before setting an empty page all-visible and all-frozen. If the VM bits were already set while PD_ALL_VISIBLE was clear, the corruption went unreported, and visibilitymap_set() could be a no-op, leaving the VM buffer clean when log_heap_prune_and_freeze() expects it to be dirty. Detect that case and repair it with heap_page_fix_vm_corruption() before setting the page all-visible. Also set the VM when PD_ALL_VISIBLE is already set but the VM bits are not both set. --- src/backend/access/heap/vacuumlazy.c | 45 ++++++++++++++++++++-------- 1 file changed, 33 insertions(+), 12 deletions(-) diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c index 997d84a77b3..ad9aa64be5a 100644 --- a/src/backend/access/heap/vacuumlazy.c +++ b/src/backend/access/heap/vacuumlazy.c @@ -1927,6 +1927,10 @@ lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, BlockNumber blkno, if (PageIsEmpty(page)) { + uint8 old_vmbits; + uint8 vmflags = VISIBILITYMAP_ALL_VISIBLE | + VISIBILITYMAP_ALL_FROZEN; + /* * It seems likely that caller will always be able to get a cleanup * lock on an empty page. But don't take any chances -- escalate to @@ -1952,7 +1956,21 @@ lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, BlockNumber blkno, * Unlike new pages, empty pages are always set all-visible and * all-frozen. */ - if (!PageIsAllVisible(page)) + old_vmbits = visibilitymap_get_status(vacrel->rel, blkno, &vmbuffer); + + /* + * If the VM is set but PD_ALL_VISIBLE is clear, fix that corruption + * first, so that we set both below in a single WAL-logged operation. + */ + if ((old_vmbits & VISIBILITYMAP_VALID_BITS) && !PageIsAllVisible(page)) + { + heap_page_fix_vm_corruption(vacrel->rel, buf, vmbuffer, + InvalidOffsetNumber, + VM_CORRUPT_MISSING_PAGE_HINT); + old_vmbits = 0; + } + + if (!PageIsAllVisible(page) || old_vmbits != vmflags) { /* Lock vmbuffer before entering critical section */ LockBuffer(vmbuffer, BUFFER_LOCK_EXCLUSIVE); @@ -1964,11 +1982,10 @@ lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, BlockNumber blkno, PageSetAllVisible(page); PageClearPrunable(page); - (void) visibilitymap_set(blkno, - vmbuffer, - VISIBILITYMAP_ALL_VISIBLE | - VISIBILITYMAP_ALL_FROZEN, - vacrel->rel->rd_locator); + + old_vmbits = visibilitymap_set(blkno, vmbuffer, vmflags, + vacrel->rel->rd_locator); + Assert(old_vmbits != vmflags); /* * Emit WAL for setting PD_ALL_VISIBLE on the heap page and @@ -1976,9 +1993,7 @@ lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, BlockNumber blkno, */ if (RelationNeedsWAL(vacrel->rel)) log_heap_prune_and_freeze(vacrel->rel, buf, - vmbuffer, - VISIBILITYMAP_ALL_VISIBLE | - VISIBILITYMAP_ALL_FROZEN, + vmbuffer, vmflags, InvalidTransactionId, /* conflict xid */ false, /* cleanup lock */ PRUNE_VACUUM_SCAN, /* reason */ @@ -1991,9 +2006,15 @@ lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, BlockNumber blkno, LockBuffer(vmbuffer, BUFFER_LOCK_UNLOCK); - /* Count the newly all-frozen pages for logging */ - vacrel->new_all_visible_pages++; - vacrel->new_all_visible_all_frozen_pages++; + /* Count only the VM bits that were newly set. */ + if (!(old_vmbits & VISIBILITYMAP_ALL_VISIBLE)) + { + vacrel->new_all_visible_pages++; + if (!(old_vmbits & VISIBILITYMAP_ALL_FROZEN)) + vacrel->new_all_visible_all_frozen_pages++; + } + else if (!(old_vmbits & VISIBILITYMAP_ALL_FROZEN)) + vacrel->new_all_frozen_pages++; } freespace = PageGetHeapFreeSpace(page); -- 2.43.0