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Tweak indexscan machinery to avoid taking an AccessShareLock on an index

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if we already have a stronger lock due to the index's table being the
update target table of the query.  Same optimization I applied earlier
at the table level.  There doesn't seem to be much interest in the more
radical idea of not locking indexes at all, so do what we can ...
This commit is contained in:
Tom Lane
2005-12-03 05:51:03 +00:00
parent 1cf65140d0
commit a98871b7ac
12 changed files with 95 additions and 35 deletions
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13
src/backend/executor/nodeBitmapIndexscan.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeBitmapIndexscan.c,v 1.13 2005/12/02 20:03:40 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/nodeBitmapIndexscan.c,v 1.14 2005/12/03 05:51:01 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -214,6 +214,7 @@ BitmapIndexScanState *
ExecInitBitmapIndexScan(BitmapIndexScan *node, EState *estate)
{
BitmapIndexScanState *indexstate;
bool relistarget;
/*
* create state structure
@ -294,13 +295,19 @@ ExecInitBitmapIndexScan(BitmapIndexScan *node, EState *estate)
indexstate->ss.ss_currentScanDesc = NULL;
/*
* open the index relation and initialize relation and scan descriptors.
* Open the index relation and initialize relation and scan descriptors.
* Note we acquire no locks here; the index machinery does its own locks
* and unlocks.
* and unlocks. (We rely on having a lock on the parent table to
* ensure the index won't go away!) Furthermore, if the parent table
* is one of the target relations of the query, then InitPlan already
* opened and write-locked the index, so we can tell the index machinery
* not to bother getting an extra lock.
*/
indexstate->biss_RelationDesc = index_open(node->indexid);
relistarget = ExecRelationIsTargetRelation(estate, node->scan.scanrelid);
indexstate->biss_ScanDesc =
index_beginscan_multi(indexstate->biss_RelationDesc,
!relistarget,
estate->es_snapshot,
indexstate->biss_NumScanKeys,
indexstate->biss_ScanKeys);