diff options
| -rw-r--r-- | src/backend/access/transam/xlog.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index fa70ab72fea..1036365896f 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.156 2004/08/04 21:33:46 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.157 2004/08/08 03:22:08 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -2187,6 +2187,15 @@ MoveOfflineLogs(uint32 log, uint32 seg, XLogRecPtr endptr) * Restore the backup blocks present in an XLOG record, if any. * * We assume all of the record has been read into memory at *record. + * + * Note: when a backup block is available in XLOG, we restore it + * unconditionally, even if the page in the database appears newer. + * This is to protect ourselves against database pages that were partially + * or incorrectly written during a crash. We assume that the XLOG data + * must be good because it has passed a CRC check, while the database + * page might not be. This will force us to replay all subsequent + * modifications of the page that appear in XLOG, rather than possibly + * ignoring them as already applied, but that's not a huge drawback. */ static void RestoreBkpBlocks(XLogRecord *record, XLogRecPtr lsn) |