Now that we've rearranged relation open to get a lock before touching
the rel, it's easy to get rid of the narrow race-condition window that used to exist in VACUUM and CLUSTER. Did some minor code-beautification work in the same area, too.
This commit is contained in:
Tom Lane
parent
e91600d1c2
commit
7aa772f03e
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.218 2006/07/31 20:08:59 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.219 2006/08/18 16:09:08 tgl Exp $
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*
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*
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* INTERFACE ROUTINES
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@ -53,6 +53,7 @@
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#include "utils/inval.h"
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#include "utils/lsyscache.h"
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#include "utils/relcache.h"
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#include "utils/syscache.h"
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static XLogRecPtr log_heap_update(Relation reln, Buffer oldbuf,
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@ -702,14 +703,56 @@ relation_open(Oid relationId, LOCKMODE lockmode)
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}
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/* ----------------
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* conditional_relation_open - open with option not to wait
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* try_relation_open - open any relation by relation OID
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*
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* As above, but if nowait is true, then throw an error rather than
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* waiting when the lock is not immediately obtainable.
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* Same as relation_open, except return NULL instead of failing
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* if the relation does not exist.
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* ----------------
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*/
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Relation
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conditional_relation_open(Oid relationId, LOCKMODE lockmode, bool nowait)
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try_relation_open(Oid relationId, LOCKMODE lockmode)
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{
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Relation r;
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Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
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/* Get the lock first */
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if (lockmode != NoLock)
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LockRelationOid(relationId, lockmode);
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/*
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* Now that we have the lock, probe to see if the relation really
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* exists or not.
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*/
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if (!SearchSysCacheExists(RELOID,
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ObjectIdGetDatum(relationId),
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0, 0, 0))
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{
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/* Release useless lock */
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if (lockmode != NoLock)
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UnlockRelationOid(relationId, lockmode);
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return NULL;
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}
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/* Should be safe to do a relcache load */
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r = RelationIdGetRelation(relationId);
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if (!RelationIsValid(r))
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elog(ERROR, "could not open relation with OID %u", relationId);
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return r;
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}
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/* ----------------
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* relation_open_nowait - open but don't wait for lock
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*
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* Same as relation_open, except throw an error instead of waiting
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* when the requested lock is not immediately obtainable.
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* ----------------
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*/
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Relation
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relation_open_nowait(Oid relationId, LOCKMODE lockmode)
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{
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Relation r;
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@ -718,27 +761,22 @@ conditional_relation_open(Oid relationId, LOCKMODE lockmode, bool nowait)
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/* Get the lock before trying to open the relcache entry */
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if (lockmode != NoLock)
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{
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if (nowait)
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if (!ConditionalLockRelationOid(relationId, lockmode))
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{
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if (!ConditionalLockRelationOid(relationId, lockmode))
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{
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/* try to throw error by name; relation could be deleted... */
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char *relname = get_rel_name(relationId);
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/* try to throw error by name; relation could be deleted... */
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char *relname = get_rel_name(relationId);
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if (relname)
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ereport(ERROR,
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(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
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errmsg("could not obtain lock on relation \"%s\"",
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relname)));
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else
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ereport(ERROR,
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(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
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errmsg("could not obtain lock on relation with OID %u",
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relationId)));
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}
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if (relname)
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ereport(ERROR,
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(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
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errmsg("could not obtain lock on relation \"%s\"",
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relname)));
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else
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ereport(ERROR,
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(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
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errmsg("could not obtain lock on relation with OID %u",
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relationId)));
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}
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else
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LockRelationOid(relationId, lockmode);
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}
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/* The relcache does all the real work... */
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/* ----------------
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* relation_openrv - open any relation specified by a RangeVar
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*
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* As above, but the relation is specified by a RangeVar.
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* Same as relation_open, but the relation is specified by a RangeVar.
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* ----------------
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*/
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Relation
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.96 2006/07/14 14:52:18 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.97 2006/08/18 16:09:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -129,20 +129,16 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt)
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CHECK_FOR_INTERRUPTS();
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/*
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* Race condition -- if the pg_class tuple has gone away since the last
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* time we saw it, we don't need to process it.
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* Open the relation, getting only a read lock on it. If the rel has
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* been dropped since we last saw it, we don't need to process it.
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*/
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if (!SearchSysCacheExists(RELOID,
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ObjectIdGetDatum(relid),
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0, 0, 0))
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onerel = try_relation_open(relid, AccessShareLock);
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if (!onerel)
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return;
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/*
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* Open the class, getting only a read lock on it, and check permissions.
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* Permissions check should match vacuum's check!
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* Check permissions --- this should match vacuum's check!
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*/
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onerel = relation_open(relid, AccessShareLock);
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if (!(pg_class_ownercheck(RelationGetRelid(onerel), GetUserId()) ||
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(pg_database_ownercheck(MyDatabaseId, GetUserId()) && !onerel->rd_rel->relisshared)))
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{
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@ -11,7 +11,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.152 2006/07/31 20:09:00 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.153 2006/08/18 16:09:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -239,6 +239,18 @@ cluster_rel(RelToCluster *rvtc, bool recheck)
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/* Check for user-requested abort. */
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CHECK_FOR_INTERRUPTS();
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/*
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* We grab exclusive access to the target rel and index for the duration
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* of the transaction. (This is redundant for the single-transaction
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* case, since cluster() already did it.) The index lock is taken inside
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* check_index_is_clusterable.
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*/
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OldHeap = try_relation_open(rvtc->tableOid, AccessExclusiveLock);
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/* If the table has gone away, we can skip processing it */
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if (!OldHeap)
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return;
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/*
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* Since we may open a new transaction for each relation, we have to check
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* that the relation still is what we think it is.
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@ -252,20 +264,23 @@ cluster_rel(RelToCluster *rvtc, bool recheck)
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HeapTuple tuple;
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Form_pg_index indexForm;
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/*
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* Check if the relation and index still exist before opening them
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*/
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if (!SearchSysCacheExists(RELOID,
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ObjectIdGetDatum(rvtc->tableOid),
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0, 0, 0) ||
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!SearchSysCacheExists(RELOID,
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ObjectIdGetDatum(rvtc->indexOid),
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0, 0, 0))
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return;
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/* Check that the user still owns the relation */
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if (!pg_class_ownercheck(rvtc->tableOid, GetUserId()))
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{
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relation_close(OldHeap, AccessExclusiveLock);
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return;
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}
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/*
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* Check that the index still exists
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*/
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if (!SearchSysCacheExists(RELOID,
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ObjectIdGetDatum(rvtc->indexOid),
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0, 0, 0))
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{
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relation_close(OldHeap, AccessExclusiveLock);
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return;
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}
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/*
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* Check that the index is still the one with indisclustered set.
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@ -273,25 +288,21 @@ cluster_rel(RelToCluster *rvtc, bool recheck)
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tuple = SearchSysCache(INDEXRELID,
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ObjectIdGetDatum(rvtc->indexOid),
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0, 0, 0);
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if (!HeapTupleIsValid(tuple))
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return; /* could have gone away... */
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if (!HeapTupleIsValid(tuple)) /* probably can't happen */
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{
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relation_close(OldHeap, AccessExclusiveLock);
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return;
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}
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indexForm = (Form_pg_index) GETSTRUCT(tuple);
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if (!indexForm->indisclustered)
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{
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ReleaseSysCache(tuple);
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relation_close(OldHeap, AccessExclusiveLock);
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return;
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}
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ReleaseSysCache(tuple);
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}
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/*
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* We grab exclusive access to the target rel and index for the duration
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* of the transaction. (This is redundant for the single- transaction
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* case, since cluster() already did it.) The index lock is taken inside
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* check_index_is_clusterable.
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*/
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OldHeap = heap_open(rvtc->tableOid, AccessExclusiveLock);
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/* Check index is valid to cluster on */
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check_index_is_clusterable(OldHeap, rvtc->indexOid, recheck);
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/lockcmds.c,v 1.14 2006/03/05 15:58:24 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/commands/lockcmds.c,v 1.15 2006/08/18 16:09:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -59,7 +59,10 @@ LockTableCommand(LockStmt *lockstmt)
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aclcheck_error(aclresult, ACL_KIND_CLASS,
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get_rel_name(reloid));
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rel = conditional_relation_open(reloid, lockstmt->mode, lockstmt->nowait);
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if (lockstmt->nowait)
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rel = relation_open_nowait(reloid, lockstmt->mode);
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else
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rel = relation_open(reloid, lockstmt->mode);
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/* Currently, we only allow plain tables to be locked */
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if (rel->rd_rel->relkind != RELKIND_RELATION)
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@ -13,7 +13,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.337 2006/07/31 20:09:00 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.338 2006/08/18 16:09:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -1041,31 +1041,12 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
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MyProc->inVacuum = true;
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}
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/*
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* Tell the cache replacement strategy that vacuum is causing all
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* following IO
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*/
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StrategyHintVacuum(true);
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/*
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* Check for user-requested abort. Note we want this to be inside a
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* transaction, so xact.c doesn't issue useless WARNING.
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*/
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CHECK_FOR_INTERRUPTS();
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/*
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* Race condition -- if the pg_class tuple has gone away since the last
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* time we saw it, we don't need to vacuum it.
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*/
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if (!SearchSysCacheExists(RELOID,
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ObjectIdGetDatum(relid),
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0, 0, 0))
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{
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StrategyHintVacuum(false);
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CommitTransactionCommand();
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||||
return;
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||||
}
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|
||||
/*
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||||
* Determine the type of lock we want --- hard exclusive lock for a FULL
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* vacuum, but just ShareUpdateExclusiveLock for concurrent vacuum. Either
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@ -1074,7 +1055,21 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
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lmode = vacstmt->full ? AccessExclusiveLock : ShareUpdateExclusiveLock;
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/*
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* Open the class, get an appropriate lock on it, and check permissions.
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* Open the relation and get the appropriate lock on it.
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*
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||||
* There's a race condition here: the rel may have gone away since
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* the last time we saw it. If so, we don't need to vacuum it.
|
||||
*/
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onerel = try_relation_open(relid, lmode);
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||||
|
||||
if (!onerel)
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||||
{
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CommitTransactionCommand();
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||||
return;
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||||
}
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||||
|
||||
/*
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||||
* Check permissions.
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||||
*
|
||||
* We allow the user to vacuum a table if he is superuser, the table
|
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* owner, or the database owner (but in the latter case, only if it's not
|
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@ -1083,8 +1078,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
|
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* Note we choose to treat permissions failure as a WARNING and keep
|
||||
* trying to vacuum the rest of the DB --- is this appropriate?
|
||||
*/
|
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onerel = relation_open(relid, lmode);
|
||||
|
||||
if (!(pg_class_ownercheck(RelationGetRelid(onerel), GetUserId()) ||
|
||||
(pg_database_ownercheck(MyDatabaseId, GetUserId()) && !onerel->rd_rel->relisshared)))
|
||||
{
|
||||
|
|
@ -1092,7 +1085,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
|
|||
(errmsg("skipping \"%s\" --- only table or database owner can vacuum it",
|
||||
RelationGetRelationName(onerel))));
|
||||
relation_close(onerel, lmode);
|
||||
StrategyHintVacuum(false);
|
||||
CommitTransactionCommand();
|
||||
return;
|
||||
}
|
||||
|
|
@ -1107,7 +1099,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
|
|||
(errmsg("skipping \"%s\" --- cannot vacuum indexes, views, or special system tables",
|
||||
RelationGetRelationName(onerel))));
|
||||
relation_close(onerel, lmode);
|
||||
StrategyHintVacuum(false);
|
||||
CommitTransactionCommand();
|
||||
return;
|
||||
}
|
||||
|
|
@ -1122,7 +1113,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
|
|||
if (isOtherTempNamespace(RelationGetNamespace(onerel)))
|
||||
{
|
||||
relation_close(onerel, lmode);
|
||||
StrategyHintVacuum(false);
|
||||
CommitTransactionCommand();
|
||||
return; /* assume no long-lived data in temp tables */
|
||||
}
|
||||
|
|
@ -1145,6 +1135,12 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
|
|||
*/
|
||||
toast_relid = onerel->rd_rel->reltoastrelid;
|
||||
|
||||
/*
|
||||
* Tell the cache replacement strategy that vacuum is causing all
|
||||
* following IO
|
||||
*/
|
||||
StrategyHintVacuum(true);
|
||||
|
||||
/*
|
||||
* Do the actual work --- either FULL or "lazy" vacuum
|
||||
*/
|
||||
|
|
@ -1153,13 +1149,14 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
|
|||
else
|
||||
lazy_vacuum_rel(onerel, vacstmt);
|
||||
|
||||
StrategyHintVacuum(false);
|
||||
|
||||
/* all done with this class, but hold lock until commit */
|
||||
relation_close(onerel, NoLock);
|
||||
|
||||
/*
|
||||
* Complete the transaction and free all temporary memory used.
|
||||
*/
|
||||
StrategyHintVacuum(false);
|
||||
CommitTransactionCommand();
|
||||
|
||||
/*
|
||||
|
|
|
|||
|
|
@ -8,7 +8,7 @@
|
|||
*
|
||||
*
|
||||
* IDENTIFICATION
|
||||
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.86 2006/07/31 20:09:05 tgl Exp $
|
||||
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.87 2006/08/18 16:09:09 tgl Exp $
|
||||
*
|
||||
*-------------------------------------------------------------------------
|
||||
*/
|
||||
|
|
@ -128,8 +128,8 @@ ConditionalLockRelationOid(Oid relid, LOCKMODE lockmode)
|
|||
/*
|
||||
* UnlockRelationId
|
||||
*
|
||||
* Note: we don't supply UnlockRelationOid since it's normally easy for
|
||||
* callers to provide the LockRelId info from a relcache entry.
|
||||
* Unlock, given a LockRelId. This is preferred over UnlockRelationOid
|
||||
* for speed reasons.
|
||||
*/
|
||||
void
|
||||
UnlockRelationId(LockRelId *relid, LOCKMODE lockmode)
|
||||
|
|
@ -141,6 +141,21 @@ UnlockRelationId(LockRelId *relid, LOCKMODE lockmode)
|
|||
LockRelease(&tag, lockmode, false);
|
||||
}
|
||||
|
||||
/*
|
||||
* UnlockRelationOid
|
||||
*
|
||||
* Unlock, given only a relation Oid. Use UnlockRelationId if you can.
|
||||
*/
|
||||
void
|
||||
UnlockRelationOid(Oid relid, LOCKMODE lockmode)
|
||||
{
|
||||
LOCKTAG tag;
|
||||
|
||||
SetLocktagRelationOid(&tag, relid);
|
||||
|
||||
LockRelease(&tag, lockmode, false);
|
||||
}
|
||||
|
||||
/*
|
||||
* LockRelation
|
||||
*
|
||||
|
|
|
|||
|
|
@ -7,7 +7,7 @@
|
|||
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
|
||||
* Portions Copyright (c) 1994, Regents of the University of California
|
||||
*
|
||||
* $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.114 2006/07/03 22:45:39 tgl Exp $
|
||||
* $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.115 2006/08/18 16:09:10 tgl Exp $
|
||||
*
|
||||
*-------------------------------------------------------------------------
|
||||
*/
|
||||
|
|
@ -129,7 +129,8 @@ typedef enum
|
|||
} LockTupleMode;
|
||||
|
||||
extern Relation relation_open(Oid relationId, LOCKMODE lockmode);
|
||||
extern Relation conditional_relation_open(Oid relationId, LOCKMODE lockmode, bool nowait);
|
||||
extern Relation try_relation_open(Oid relationId, LOCKMODE lockmode);
|
||||
extern Relation relation_open_nowait(Oid relationId, LOCKMODE lockmode);
|
||||
extern Relation relation_openrv(const RangeVar *relation, LOCKMODE lockmode);
|
||||
extern void relation_close(Relation relation, LOCKMODE lockmode);
|
||||
|
||||
|
|
|
|||
|
|
@ -7,7 +7,7 @@
|
|||
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
|
||||
* Portions Copyright (c) 1994, Regents of the University of California
|
||||
*
|
||||
* $PostgreSQL: pgsql/src/include/storage/lmgr.h,v 1.55 2006/07/31 20:09:05 tgl Exp $
|
||||
* $PostgreSQL: pgsql/src/include/storage/lmgr.h,v 1.56 2006/08/18 16:09:13 tgl Exp $
|
||||
*
|
||||
*-------------------------------------------------------------------------
|
||||
*/
|
||||
|
|
@ -24,6 +24,7 @@ extern void RelationInitLockInfo(Relation relation);
|
|||
extern void LockRelationOid(Oid relid, LOCKMODE lockmode);
|
||||
extern bool ConditionalLockRelationOid(Oid relid, LOCKMODE lockmode);
|
||||
extern void UnlockRelationId(LockRelId *relid, LOCKMODE lockmode);
|
||||
extern void UnlockRelationOid(Oid relid, LOCKMODE lockmode);
|
||||
|
||||
extern void LockRelation(Relation relation, LOCKMODE lockmode);
|
||||
extern bool ConditionalLockRelation(Relation relation, LOCKMODE lockmode);
|
||||
|
|
|
|||
Loading…
Reference in New Issue