diff options
Diffstat (limited to 'src/backend/executor/execUtils.c')
| -rw-r--r-- | src/backend/executor/execUtils.c | 92 |
1 files changed, 90 insertions, 2 deletions
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c index 5221624fc7d..c814b971472 100644 --- a/src/backend/executor/execUtils.c +++ b/src/backend/executor/execUtils.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.129 2005/11/23 20:27:57 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.130 2005/12/02 20:03:40 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -24,6 +24,9 @@ * ExecAssignResultType * etc * + * ExecOpenScanRelation Common code for scan node init routines. + * ExecCloseScanRelation + * * ExecOpenIndices \ * ExecCloseIndices | referenced by InitPlan, EndPlan, * ExecInsertIndexTuples / ExecInsert, ExecUpdate @@ -45,6 +48,7 @@ #include "catalog/pg_index.h" #include "executor/execdebug.h" #include "miscadmin.h" +#include "parser/parsetree.h" #include "utils/builtins.h" #include "utils/fmgroids.h" #include "utils/memutils.h" @@ -685,6 +689,90 @@ ExecAssignScanTypeFromOuterPlan(ScanState *scanstate) /* ---------------------------------------------------------------- + * Scan node support + * ---------------------------------------------------------------- + */ + +/* ---------------------------------------------------------------- + * ExecOpenScanRelation + * + * Open the heap relation to be scanned by a base-level scan plan node. + * This should be called during the node's ExecInit routine. + * + * By default, this acquires AccessShareLock on the relation. However, + * if the relation was already locked by InitPlan, we don't need to acquire + * any additional lock. This saves trips to the shared lock manager. + * ---------------------------------------------------------------- + */ +Relation +ExecOpenScanRelation(EState *estate, Index scanrelid) +{ + RangeTblEntry *rtentry; + Oid reloid; + LOCKMODE lockmode; + ResultRelInfo *resultRelInfos; + int i; + + /* + * First determine the lock type we need. Scan to see if target relation + * is either a result relation or a FOR UPDATE/FOR SHARE relation. + */ + lockmode = AccessShareLock; + resultRelInfos = estate->es_result_relations; + for (i = 0; i < estate->es_num_result_relations; i++) + { + if (resultRelInfos[i].ri_RangeTableIndex == scanrelid) + { + lockmode = NoLock; + break; + } + } + + if (lockmode == AccessShareLock) + { + ListCell *l; + + foreach(l, estate->es_rowMarks) + { + ExecRowMark *erm = lfirst(l); + + if (erm->rti == scanrelid) + { + lockmode = NoLock; + break; + } + } + } + + /* OK, open the relation and acquire lock as needed */ + rtentry = rt_fetch(scanrelid, estate->es_range_table); + reloid = rtentry->relid; + + return heap_open(reloid, lockmode); +} + +/* ---------------------------------------------------------------- + * ExecCloseScanRelation + * + * Close the heap relation scanned by a base-level scan plan node. + * This should be called during the node's ExecEnd routine. + * + * Currently, we do not release the lock acquired by ExecOpenScanRelation. + * This lock should be held till end of transaction. (There is a faction + * that considers this too much locking, however.) + * + * If we did want to release the lock, we'd have to repeat the logic in + * ExecOpenScanRelation in order to figure out what to release. + * ---------------------------------------------------------------- + */ +void +ExecCloseScanRelation(Relation scanrel) +{ + heap_close(scanrel, NoLock); +} + + +/* ---------------------------------------------------------------- * ExecInsertIndexTuples support * ---------------------------------------------------------------- */ @@ -760,7 +848,7 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo) * * If the index AM is not safe for concurrent updates, obtain an * exclusive lock on the index to lock out other updaters as well as - * readers (index_beginscan places AccessShareLock). + * readers (index_beginscan places AccessShareLock on the index). * * If there are multiple not-concurrent-safe indexes, all backends * must lock the indexes in the same order or we will get deadlocks |