diff options
| author | Tom Lane | 2016-05-24 19:20:12 +0000 |
|---|---|---|
| committer | Tom Lane | 2016-05-24 19:20:36 +0000 |
| commit | 996d273978c6f21b8b66f7f3bdd979cc37736c7a (patch) | |
| tree | 1ed83bb05d282ccb28cc1a4e63a7a5fc3c6bf299 | |
| parent | 0c7cd45b6d702253c09427929bcceb6e7fe9029a (diff) | |
Avoid consuming an XID during vac_truncate_clog().
vac_truncate_clog() uses its own transaction ID as the comparison point in
a sanity check that no database's datfrozenxid has already wrapped around
"into the future". That was probably fine when written, but in a lazy
vacuum we won't have assigned an XID, so calling GetCurrentTransactionId()
causes an XID to be assigned when otherwise one would not be. Most of the
time that's not a big problem ... but if we are hard up against the
wraparound limit, consuming XIDs during antiwraparound vacuums is a very
bad thing.
Instead, use ReadNewTransactionId(), which not only avoids this problem
but is in itself a better comparison point to test whether wraparound
has already occurred.
Report and patch by Alexander Korotkov. Back-patch to all versions.
Report: <CAPpHfdspOkmiQsxh-UZw2chM6dRMwXAJGEmmbmqYR=yvM7-s6A@mail.gmail.com>
| -rw-r--r-- | src/backend/commands/vacuum.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c index 93361a0c99..9cda925032 100644 --- a/src/backend/commands/vacuum.c +++ b/src/backend/commands/vacuum.c @@ -1051,7 +1051,7 @@ vac_truncate_clog(TransactionId frozenXID, TransactionId lastSaneFrozenXid, MultiXactId lastSaneMinMulti) { - TransactionId myXID = GetCurrentTransactionId(); + TransactionId nextXID = ReadNewTransactionId(); Relation relation; HeapScanDesc scan; HeapTuple tuple; @@ -1100,7 +1100,7 @@ vac_truncate_clog(TransactionId frozenXID, MultiXactIdPrecedes(lastSaneMinMulti, dbform->datminmxid)) bogus = true; - if (TransactionIdPrecedes(myXID, dbform->datfrozenxid)) + if (TransactionIdPrecedes(nextXID, dbform->datfrozenxid)) frozenAlreadyWrapped = true; else if (TransactionIdPrecedes(dbform->datfrozenxid, frozenXID)) { |