diff options
Diffstat (limited to 'src/backend/access/transam/clog.c')
| -rw-r--r-- | src/backend/access/transam/clog.c | 22 |
1 files changed, 19 insertions, 3 deletions
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c index 07581e4444a..a403838bd79 100644 --- a/src/backend/access/transam/clog.c +++ b/src/backend/access/transam/clog.c @@ -13,7 +13,7 @@ * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Header: /cvsroot/pgsql/src/backend/access/transam/clog.c,v 1.2 2001/08/25 23:24:39 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/transam/clog.c,v 1.3 2001/08/26 16:55:59 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -762,8 +762,12 @@ ExtendCLOG(TransactionId newestXact) { int pageno; - /* No work except at first XID of a page */ - if (TransactionIdToPgIndex(newestXact) != 0) + /* + * No work except at first XID of a page. But beware: just after + * wraparound, the first XID of page zero is FirstNormalTransactionId. + */ + if (TransactionIdToPgIndex(newestXact) != 0 && + !TransactionIdEquals(newestXact, FirstNormalTransactionId)) return; pageno = TransactionIdToPage(newestXact); @@ -818,6 +822,18 @@ TruncateCLOG(TransactionId oldestXact) S_LOCK(&(ClogCtl->control_lck)); restart:; + /* + * While we are holding the lock, make an important safety check: + * the planned cutoff point must be <= the current CLOG endpoint page. + * Otherwise we have already wrapped around, and proceeding with the + * truncation would risk removing the current CLOG segment. + */ + if (CLOGPagePrecedes(ClogCtl->latest_page_number, cutoffPage)) + { + S_UNLOCK(&(ClogCtl->control_lck)); + elog(LOG, "unable to truncate commit log: apparent wraparound"); + return; + } for (slotno = 0; slotno < NUM_CLOG_BUFFERS; slotno++) { |