diff options
| -rw-r--r-- | src/backend/postmaster/autovacuum.c | 21 | ||||
| -rw-r--r-- | src/backend/storage/lmgr/lmgr.c | 38 | ||||
| -rw-r--r-- | src/include/storage/lmgr.h | 2 |
3 files changed, 60 insertions, 1 deletions
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c index ae9be9b9113..7dd9345c617 100644 --- a/src/backend/postmaster/autovacuum.c +++ b/src/backend/postmaster/autovacuum.c @@ -76,6 +76,7 @@ #include "catalog/dependency.h" #include "catalog/namespace.h" #include "catalog/pg_database.h" +#include "catalog/pg_namespace.h" #include "commands/dbcommands.h" #include "commands/vacuum.h" #include "lib/ilist.h" @@ -2329,6 +2330,24 @@ do_autovacuum(void) continue; } + /* + * Try to lock the temp namespace, too. Even though we have lock on + * the table itself, there's a risk of deadlock against an incoming + * backend trying to clean out the temp namespace, in case this table + * has dependencies (such as sequences) that the backend's + * performDeletion call might visit in a different order. If we can + * get AccessShareLock on the namespace, that's sufficient to ensure + * we're not running concurrently with RemoveTempRelations. If we + * can't, back off and let RemoveTempRelations do its thing. + */ + if (!ConditionalLockDatabaseObject(NamespaceRelationId, + classForm->relnamespace, 0, + AccessShareLock)) + { + UnlockRelationOid(relid, AccessExclusiveLock); + continue; + } + /* OK, let's delete it */ ereport(LOG, (errmsg("autovacuum: dropping orphan temp table \"%s.%s.%s\"", @@ -2346,7 +2365,7 @@ do_autovacuum(void) /* * To commit the deletion, end current transaction and start a new - * one. Note this also releases the lock we took. + * one. Note this also releases the locks we took. */ CommitTransactionCommand(); StartTransactionCommand(); diff --git a/src/backend/storage/lmgr/lmgr.c b/src/backend/storage/lmgr/lmgr.c index ee9b89a6726..2da91eb492d 100644 --- a/src/backend/storage/lmgr/lmgr.c +++ b/src/backend/storage/lmgr/lmgr.c @@ -1020,6 +1020,44 @@ LockDatabaseObject(Oid classid, Oid objid, uint16 objsubid, } /* + * ConditionalLockDatabaseObject + * + * As above, but only lock if we can get the lock without blocking. + * Returns true iff the lock was acquired. + */ +bool +ConditionalLockDatabaseObject(Oid classid, Oid objid, uint16 objsubid, + LOCKMODE lockmode) +{ + LOCKTAG tag; + LOCALLOCK *locallock; + LockAcquireResult res; + + SET_LOCKTAG_OBJECT(tag, + MyDatabaseId, + classid, + objid, + objsubid); + + res = LockAcquireExtended(&tag, lockmode, false, true, true, &locallock); + + if (res == LOCKACQUIRE_NOT_AVAIL) + return false; + + /* + * Now that we have the lock, check for invalidation messages; see notes + * in LockRelationOid. + */ + if (res != LOCKACQUIRE_ALREADY_CLEAR) + { + AcceptInvalidationMessages(); + MarkLockClear(locallock); + } + + return true; +} + +/* * UnlockDatabaseObject */ void diff --git a/src/include/storage/lmgr.h b/src/include/storage/lmgr.h index 4ee91e3cf93..8ab833d1d4a 100644 --- a/src/include/storage/lmgr.h +++ b/src/include/storage/lmgr.h @@ -93,6 +93,8 @@ extern void SpeculativeInsertionWait(TransactionId xid, uint32 token); /* Lock a general object (other than a relation) of the current database */ extern void LockDatabaseObject(Oid classid, Oid objid, uint16 objsubid, LOCKMODE lockmode); +extern bool ConditionalLockDatabaseObject(Oid classid, Oid objid, + uint16 objsubid, LOCKMODE lockmode); extern void UnlockDatabaseObject(Oid classid, Oid objid, uint16 objsubid, LOCKMODE lockmode); |