From 86073a2b7acc58fce8701a9207a46adb41fbd8cc Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Wed, 29 Feb 2012 15:22:49 +0200 Subject: [PATCH] Correctly detect SSI conflicts of prepared transactions after crash. A prepared transaction can get new conflicts in and out after preparing, so we cannot rely on the in- and out-flags stored in the statefile at prepare- time. As a quick fix, make the conservative assumption that after a restart, all prepared transactions are considered to have both in- and out-conflicts. That can lead to unnecessary rollbacks after a crash, but that shouldn't be a big problem in practice; you don't want prepared transactions to hang around for a long time anyway. Dan Ports --- src/backend/storage/lmgr/predicate.c | 31 ++++++++++++++-------------- 1 file changed, 15 insertions(+), 16 deletions(-) diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c index 27124672da..532dedf959 100644 --- a/src/backend/storage/lmgr/predicate.c +++ b/src/backend/storage/lmgr/predicate.c @@ -4659,14 +4659,11 @@ AtPrepare_PredicateLocks(void) xactRecord->flags = MySerializableXact->flags; /* - * Tweak the flags. Since we're not going to output the inConflicts and - * outConflicts lists, if they're non-empty we'll represent that by - * setting the appropriate summary conflict flags. + * Note that we don't include the list of conflicts in our out in + * the statefile, because new conflicts can be added even after the + * transaction prepares. We'll just make a conservative assumption + * during recovery instead. */ - if (!SHMQueueEmpty(&MySerializableXact->inConflicts)) - xactRecord->flags |= SXACT_FLAG_SUMMARY_CONFLICT_IN; - if (!SHMQueueEmpty(&MySerializableXact->outConflicts)) - xactRecord->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT; RegisterTwoPhaseRecord(TWOPHASE_RM_PREDICATELOCK_ID, 0, &record, sizeof(record)); @@ -4801,15 +4798,6 @@ predicatelock_twophase_recover(TransactionId xid, uint16 info, sxact->SeqNo.lastCommitBeforeSnapshot = RecoverySerCommitSeqNo; - - /* - * We don't need the details of a prepared transaction's conflicts, - * just whether it had conflicts in or out (which we get from the - * flags) - */ - SHMQueueInit(&(sxact->outConflicts)); - SHMQueueInit(&(sxact->inConflicts)); - /* * Don't need to track this; no transactions running at the time the * recovered xact started are still active, except possibly other @@ -4831,6 +4819,17 @@ predicatelock_twophase_recover(TransactionId xid, uint16 info, (MaxBackends + max_prepared_xacts)); } + /* + * We don't know whether the transaction had any conflicts or + * not, so we'll conservatively assume that it had both a + * conflict in and a conflict out, and represent that with the + * summary conflict flags. + */ + SHMQueueInit(&(sxact->outConflicts)); + SHMQueueInit(&(sxact->inConflicts)); + sxact->flags |= SXACT_FLAG_SUMMARY_CONFLICT_IN; + sxact->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT; + /* Register the transaction's xid */ sxidtag.xid = xid; sxid = (SERIALIZABLEXID *) hash_search(SerializableXidHash, -- 2.40.0