diff options
Diffstat (limited to 'src/backend/commands/vacuumlazy.c')
| -rw-r--r-- | src/backend/commands/vacuumlazy.c | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c index cc1852f65a1..891def15344 100644 --- a/src/backend/commands/vacuumlazy.c +++ b/src/backend/commands/vacuumlazy.c @@ -31,7 +31,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/commands/vacuumlazy.c,v 1.32 2003/09/25 06:57:59 petere Exp $ + * $Header: /cvsroot/pgsql/src/backend/commands/vacuumlazy.c,v 1.32.2.1 2005/05/07 21:33:21 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -254,8 +254,30 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats, if (PageIsNew(page)) { - /* Not sure we still need to handle this case, but... */ + /* + * An all-zeroes page could be left over if a backend extends + * the relation but crashes before initializing the page. + * Reclaim such pages for use. + * + * We have to be careful here because we could be looking at + * a page that someone has just added to the relation and not + * yet been able to initialize (see RelationGetBufferForTuple). + * To interlock against that, release the buffer read lock + * (which we must do anyway) and grab the relation extension + * lock before re-locking in exclusive mode. If the page is + * still uninitialized by then, it must be left over from a + * crashed backend, and we can initialize it. + * + * We don't really need the relation lock when this is a new + * or temp relation, but it's probably not worth the code space + * to check that, since this surely isn't a critical path. + * + * Note: the comparable code in vacuum.c need not do all this + * because it's got exclusive lock on the whole relation. + */ LockBuffer(buf, BUFFER_LOCK_UNLOCK); + LockPage(onerel, 0, ExclusiveLock); + UnlockPage(onerel, 0, ExclusiveLock); LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE); if (PageIsNew(page)) { |