diff options
Diffstat (limited to 'src/backend/executor/execAmi.c')
| -rw-r--r-- | src/backend/executor/execAmi.c | 44 |
1 files changed, 21 insertions, 23 deletions
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c index cb47eda5c66..a396ec78719 100644 --- a/src/backend/executor/execAmi.c +++ b/src/backend/executor/execAmi.c @@ -6,7 +6,7 @@ * Portions Copyright (c) 1996-2000, PostgreSQL, Inc * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: execAmi.c,v 1.54 2000/10/26 21:35:15 tgl Exp $ + * $Id: execAmi.c,v 1.55 2000/11/08 22:09:57 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -61,11 +61,8 @@ static Pointer ExecBeginScan(Relation relation, int nkeys, ScanKey skeys, * nkeys -- number of keys * skeys -- keys to restrict scanning * isindex -- if this is true, the relation is the relid of - * an index relation, else it is an index into the - * range table. + * an index relation, else it is a heap relation. * Returns the relation as(relDesc scanDesc) - * If this structure is changed, need to modify the access macros - * defined in execInt.h. * ---------------------------------------------------------------- */ void @@ -90,16 +87,19 @@ ExecOpenScanR(Oid relOid, */ /* ---------------- - * open the relation with the correct call depending + * Open the relation with the correct call depending * on whether this is a heap relation or an index relation. * - * Do not lock the rel here; beginscan will acquire AccessShareLock. + * For a table, acquire AccessShareLock for the duration of the query + * execution. For indexes, acquire no lock here; the index machinery + * does its own locks and unlocks. (We rely on having some kind of + * lock on the parent table to ensure the index won't go away!) * ---------------- */ if (isindex) relation = index_open(relOid); else - relation = heap_open(relOid, NoLock); + relation = heap_open(relOid, AccessShareLock); scanDesc = ExecBeginScan(relation, nkeys, @@ -136,8 +136,6 @@ ExecBeginScan(Relation relation, { Pointer scanDesc; - scanDesc = NULL; - /* ---------------- * open the appropriate type of scan. * @@ -183,12 +181,11 @@ ExecCloseR(Plan *node) HeapScanDesc scanDesc; /* ---------------- - * shut down the heap scan and close the heap relation + * get state for node and shut down the heap scan, if any * ---------------- */ switch (nodeTag(node)) { - case T_SeqScan: state = ((SeqScan *) node)->scanstate; break; @@ -212,18 +209,9 @@ ExecCloseR(Plan *node) if (scanDesc != NULL) heap_endscan(scanDesc); - /* - * endscan released AccessShareLock acquired by beginscan. If we are - * holding any stronger locks on the rel, they should be held till end - * of xact. Therefore, we need only close the rel and not release - * locks. - */ - if (relation != NULL) - heap_close(relation, NoLock); - /* ---------------- * if this is an index scan then we have to take care - * of the index relations as well.. + * of the index relations as well. * ---------------- */ if (IsA(node, IndexScan)) @@ -242,7 +230,7 @@ ExecCloseR(Plan *node) for (i = 0; i < numIndices; i++) { /* ---------------- - * shut down each of the scans and + * shut down each of the index scans and * close each of the index relations * ---------------- */ @@ -253,6 +241,16 @@ ExecCloseR(Plan *node) index_close(indexRelationDescs[i]); } } + + /* + * Finally, close the heap relation. + * + * Currently, we do not release the AccessShareLock acquired by + * ExecOpenScanR. This lock should be held till end of transaction. + * (There is a faction that considers this too much locking, however.) + */ + if (relation != NULL) + heap_close(relation, NoLock); } /* ---------------------------------------------------------------- |