postgres.git / summary / log / commit / refs

commit    e5d06f2b12a7c75f2b0c7fd2055a14efaa2b59ec
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Wed Dec 30 22:32:23 2015 +0000
First released in: 9.6.0

    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 a93d4a1f238..2a8cab746a9 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 */


[parent: e842908233bb]