diff options
Diffstat (limited to 'src/backend/access/heap/heapam.c')
| -rw-r--r-- | src/backend/access/heap/heapam.c | 91 |
1 files changed, 70 insertions, 21 deletions
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index d8dc24c41f0..092a23cc0ec 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -7,7 +7,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.53 1999/07/19 07:07:18 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.54 1999/09/18 19:05:58 tgl Exp $ * * * INTERFACE ROUTINES @@ -486,15 +486,20 @@ heapgettup(Relation relation, /* ---------------- * heap_open - open a heap relation by relationId * - * presently the relcache routines do all the work we need - * to open/close heap relations. + * If lockmode is "NoLock", no lock is obtained on the relation, + * and the caller must check for a NULL return value indicating + * that no such relation exists. + * Otherwise, an error is raised if the relation does not exist, + * and the specified kind of lock is obtained on the relation. * ---------------- */ Relation -heap_open(Oid relationId) +heap_open(Oid relationId, LOCKMODE lockmode) { Relation r; + Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES); + /* ---------------- * increment access statistics * ---------------- @@ -502,26 +507,41 @@ heap_open(Oid relationId) IncrHeapAccessStat(local_open); IncrHeapAccessStat(global_open); - r = (Relation) RelationIdGetRelation(relationId); + /* The relcache does all the real work... */ + r = RelationIdGetRelation(relationId); + /* Under no circumstances will we return an index as a relation. */ if (RelationIsValid(r) && r->rd_rel->relkind == RELKIND_INDEX) elog(ERROR, "%s is an index relation", r->rd_rel->relname.data); + if (lockmode == NoLock) + return r; /* caller must check RelationIsValid! */ + + if (! RelationIsValid(r)) + elog(ERROR, "Relation %u does not exist", relationId); + + LockRelation(r, lockmode); + return r; } /* ---------------- * heap_openr - open a heap relation by name * - * presently the relcache routines do all the work we need - * to open/close heap relations. + * If lockmode is "NoLock", no lock is obtained on the relation, + * and the caller must check for a NULL return value indicating + * that no such relation exists. + * Otherwise, an error is raised if the relation does not exist, + * and the specified kind of lock is obtained on the relation. * ---------------- */ Relation -heap_openr(char *relationName) +heap_openr(char *relationName, LOCKMODE lockmode) { Relation r; + Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES); + /* ---------------- * increment access statistics * ---------------- @@ -529,24 +549,37 @@ heap_openr(char *relationName) IncrHeapAccessStat(local_openr); IncrHeapAccessStat(global_openr); + /* The relcache does all the real work... */ r = RelationNameGetRelation(relationName); + /* Under no circumstances will we return an index as a relation. */ if (RelationIsValid(r) && r->rd_rel->relkind == RELKIND_INDEX) elog(ERROR, "%s is an index relation", r->rd_rel->relname.data); + if (lockmode == NoLock) + return r; /* caller must check RelationIsValid! */ + + if (! RelationIsValid(r)) + elog(ERROR, "Relation '%s' does not exist", relationName); + + LockRelation(r, lockmode); + return r; } /* ---------------- * heap_close - close a heap relation * - * presently the relcache routines do all the work we need - * to open/close heap relations. + * If lockmode is not "NoLock", we first release the specified lock. + * Note that it is often sensible to hold a lock beyond heap_close; + * in that case, the lock is released automatically at xact end. * ---------------- */ void -heap_close(Relation relation) +heap_close(Relation relation, LOCKMODE lockmode) { + Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES); + /* ---------------- * increment access statistics * ---------------- @@ -554,6 +587,10 @@ heap_close(Relation relation) IncrHeapAccessStat(local_close); IncrHeapAccessStat(global_close); + if (lockmode != NoLock) + UnlockRelation(relation, lockmode); + + /* The relcache does the real work... */ RelationClose(relation); } @@ -582,15 +619,9 @@ heap_beginscan(Relation relation, * sanity checks * ---------------- */ - if (RelationIsValid(relation) == false) + if (! RelationIsValid(relation)) elog(ERROR, "heap_beginscan: !RelationIsValid(relation)"); - LockRelation(relation, AccessShareLock); - - /* XXX someday assert SelfTimeQual if relkind == RELKIND_UNCATALOGED */ - if (relation->rd_rel->relkind == RELKIND_UNCATALOGED) - snapshot = SnapshotSelf; - /* ---------------- * increment relation ref count while scanning relation * ---------------- @@ -598,6 +629,20 @@ heap_beginscan(Relation relation, RelationIncrementReferenceCount(relation); /* ---------------- + * Acquire AccessShareLock for the duration of the scan + * + * Note: we could get an SI inval message here and consequently have + * to rebuild the relcache entry. The refcount increment above + * ensures that we will rebuild it and not just flush it... + * ---------------- + */ + LockRelation(relation, AccessShareLock); + + /* XXX someday assert SelfTimeQual if relkind == RELKIND_UNCATALOGED */ + if (relation->rd_rel->relkind == RELKIND_UNCATALOGED) + snapshot = SnapshotSelf; + + /* ---------------- * allocate and initialize scan descriptor * ---------------- */ @@ -684,14 +729,18 @@ heap_endscan(HeapScanDesc scan) unpinscan(scan); /* ---------------- + * Release AccessShareLock acquired by heap_beginscan() + * ---------------- + */ + UnlockRelation(scan->rs_rd, AccessShareLock); + + /* ---------------- * decrement relation reference count and free scan descriptor storage * ---------------- */ RelationDecrementReferenceCount(scan->rs_rd); - UnlockRelation(scan->rs_rd, AccessShareLock); - - pfree(scan); /* XXX */ + pfree(scan); } /* ---------------- |