From e5d06f2b12a7c75f2b0c7fd2055a14efaa2b59ec Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 30 Dec 2015 17:32:23 -0500 Subject: [PATCH] Dept of second thoughts: the !scan_all exit mustn't increase scanned_pages. In the extreme edge case where contended pages are the only ones that escape being scanned, the previous commit would have allowed us to think that relfrozenxid could be advanced, which is exactly wrong. --- src/backend/commands/vacuumlazy.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c index a93d4a1f23..2a8cab746a 100644 --- a/src/backend/commands/vacuumlazy.c +++ b/src/backend/commands/vacuumlazy.c @@ -666,7 +666,7 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats, * to use lazy_check_needs_freeze() for both situations, though. */ LockBuffer(buf, BUFFER_LOCK_SHARE); - if (!lazy_check_needs_freeze(buf, &hastup) || !scan_all) + if (!lazy_check_needs_freeze(buf, &hastup)) { UnlockReleaseBuffer(buf); vacrelstats->scanned_pages++; @@ -675,6 +675,18 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats, vacrelstats->nonempty_pages = blkno + 1; continue; } + if (!scan_all) + { + /* + * Here, we must not advance scanned_pages; that would amount + * to claiming that the page contains no freezable tuples. + */ + UnlockReleaseBuffer(buf); + vacrelstats->pinskipped_pages++; + if (hastup) + vacrelstats->nonempty_pages = blkno + 1; + continue; + } LockBuffer(buf, BUFFER_LOCK_UNLOCK); LockBufferForCleanup(buf); /* drop through to normal processing */