database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-10-19 15:49:24 +03:00
Code Activity

Reduce lock levels of some ALTER TABLE cmds

Browse Source 
VALIDATE CONSTRAINT

CLUSTER ON
SET WITHOUT CLUSTER

ALTER COLUMN SET STATISTICS
ALTER COLUMN SET ()
ALTER COLUMN RESET ()

All other sub-commands use AccessExclusiveLock

Simon Riggs and Noah Misch

Reviews by Robert Haas and Andres Freund
This commit is contained in:
Simon Riggs
2014-04-06 11:13:43 -04:00
parent 80a5cf643a
commit e5550d5fec
13 changed files with 402 additions and 120 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
src/backend/utils/adt/ruleutils.c
View File

@@ -54,6 +54,7 @@
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
#include "utils/tqual.h"
#include "utils/typcache.h"
@@ -1284,6 +1285,9 @@ pg_get_constraintdef_string(Oid constraintId)
return pg_get_constraintdef_worker(constraintId, true, 0);
}
/*
* As of 9.4, we now use an MVCC snapshot for this.
*/
static char *
pg_get_constraintdef_worker(Oid constraintId, bool fullCommand,
int prettyFlags)
@@ -1291,10 +1295,34 @@ pg_get_constraintdef_worker(Oid constraintId, bool fullCommand,
HeapTuple tup;
Form_pg_constraint conForm;
StringInfoData buf;
SysScanDesc scandesc;
ScanKeyData scankey[1];
Snapshot snapshot = RegisterSnapshot(GetTransactionSnapshot());
Relation relation = heap_open(ConstraintRelationId, AccessShareLock);
ScanKeyInit(&scankey[0],
ObjectIdAttributeNumber,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(constraintId));
scandesc = systable_beginscan(relation,
ConstraintOidIndexId,
true,
snapshot,
1,
scankey);
/*
* We later use the tuple with SysCacheGetAttr() as if we
* had obtained it via SearchSysCache, which works fine.
*/
tup = systable_getnext(scandesc);
UnregisterSnapshot(snapshot);
tup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(constraintId));
if (!HeapTupleIsValid(tup)) /* should not happen */
elog(ERROR, "cache lookup failed for constraint %u", constraintId);
conForm = (Form_pg_constraint) GETSTRUCT(tup);
initStringInfo(&buf);
@@ -1575,7 +1603,8 @@ pg_get_constraintdef_worker(Oid constraintId, bool fullCommand,
appendStringInfoString(&buf, " NOT VALID");
/* Cleanup */
ReleaseSysCache(tup);
systable_endscan(scandesc);
heap_close(relation, AccessShareLock);
return buf.data;
}