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Replace pg_class.reltriggers with relhastriggers, which is just a boolean hint

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("there might be triggers") rather than an exact count.  This is necessary
catalog infrastructure for the upcoming patch to reduce the strength of
locking needed for trigger addition/removal.  Split out and committed
separately for ease of reviewing/testing.

In passing, also get rid of the unused pg_class columns relukeys, relfkeys,
and relrefs, which haven't been maintained in many years and now have no
chance of ever being maintained (because of wishing to avoid locking).

Simon Riggs
This commit is contained in:
Tom Lane
2008-11-09 21:24:33 +00:00
parent 1d577f5e49
commit e4718f2c9e
13 changed files with 162 additions and 197 deletions
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94
src/backend/commands/trigger.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.239 2008/11/02 01:45:28 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.240 2008/11/09 21:24:32 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -95,7 +95,6 @@ CreateTrigger(CreateTrigStmt *stmt, Oid constraintOid)
Oid funcoid;
Oid funcrettype;
Oid trigoid;
int found = 0;
int i;
char constrtrigname[NAMEDATALEN];
char *trigname;
@ -280,10 +279,9 @@ CreateTrigger(CreateTrigStmt *stmt, Oid constraintOid)
}
/*
* Scan pg_trigger for existing triggers on relation. We do this mainly
* because we must count them; a secondary benefit is to give a nice error
* message if there's already a trigger of the same name. (The unique
* index on tgrelid/tgname would complain anyway.)
* Scan pg_trigger for existing triggers on relation. We do this only
* to give a nice error message if there's already a trigger of the same
* name. (The unique index on tgrelid/tgname would complain anyway.)
*
* NOTE that this is cool only because we have AccessExclusiveLock on the
* relation, so the trigger set won't be changing underneath us.
@ -303,7 +301,6 @@ CreateTrigger(CreateTrigStmt *stmt, Oid constraintOid)
(errcode(ERRCODE_DUPLICATE_OBJECT),
errmsg("trigger \"%s\" for relation \"%s\" already exists",
trigname, stmt->relation->relname)));
found++;
}
systable_endscan(tgscan);
@ -405,7 +402,7 @@ CreateTrigger(CreateTrigStmt *stmt, Oid constraintOid)
elog(ERROR, "cache lookup failed for relation %u",
RelationGetRelid(rel));
((Form_pg_class) GETSTRUCT(tuple))->reltriggers = found + 1;
((Form_pg_class) GETSTRUCT(tuple))->relhastriggers = true;
simple_heap_update(pgrel, &tuple->t_self, tuple);
@ -818,9 +815,6 @@ RemoveTriggerById(Oid trigOid)
HeapTuple tup;
Oid relid;
Relation rel;
Relation pgrel;
HeapTuple tuple;
Form_pg_class classForm;
tgrel = heap_open(TriggerRelationId, RowExclusiveLock);
@ -867,33 +861,15 @@ RemoveTriggerById(Oid trigOid)
heap_close(tgrel, RowExclusiveLock);
/*
* Update relation's pg_class entry. Crucial side-effect: other backends
* (and this one too!) are sent SI message to make them rebuild relcache
* entries.
*
* Note this is OK only because we have AccessExclusiveLock on the rel, so
* no one else is creating/deleting triggers on this rel at the same time.
* We do not bother to try to determine whether any other triggers remain,
* which would be needed in order to decide whether it's safe to clear
* the relation's relhastriggers. (In any case, there might be a
* concurrent process adding new triggers.) Instead, just force a
* relcache inval to make other backends (and this one too!) rebuild
* their relcache entries. There's no great harm in leaving relhastriggers
* true even if there are no triggers left.
*/
pgrel = heap_open(RelationRelationId, RowExclusiveLock);
tuple = SearchSysCacheCopy(RELOID,
ObjectIdGetDatum(relid),
0, 0, 0);
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for relation %u", relid);
classForm = (Form_pg_class) GETSTRUCT(tuple);
if (classForm->reltriggers == 0) /* should not happen */
elog(ERROR, "relation \"%s\" has reltriggers = 0",
RelationGetRelationName(rel));
classForm->reltriggers--;
simple_heap_update(pgrel, &tuple->t_self, tuple);
CatalogUpdateIndexes(pgrel, tuple);
heap_freetuple(tuple);
heap_close(pgrel, RowExclusiveLock);
CacheInvalidateRelcache(rel);
/* Keep lock on trigger's rel until end of xact */
heap_close(rel, NoLock);
@ -1134,18 +1110,23 @@ void
RelationBuildTriggers(Relation relation)
{
TriggerDesc *trigdesc;
int ntrigs = relation->rd_rel->reltriggers;
int numtrigs;
int maxtrigs;
Trigger *triggers;
int found = 0;
Relation tgrel;
ScanKeyData skey;
SysScanDesc tgscan;
HeapTuple htup;
MemoryContext oldContext;
int i;
Assert(ntrigs > 0); /* else I should not have been called */
triggers = (Trigger *) palloc(ntrigs * sizeof(Trigger));
/*
* Allocate a working array to hold the triggers (the array is extended
* if necessary)
*/
maxtrigs = 16;
triggers = (Trigger *) palloc(maxtrigs * sizeof(Trigger));
numtrigs = 0;
/*
* Note: since we scan the triggers using TriggerRelidNameIndexId, we will
@ -1167,10 +1148,12 @@ RelationBuildTriggers(Relation relation)
Form_pg_trigger pg_trigger = (Form_pg_trigger) GETSTRUCT(htup);
Trigger *build;
if (found >= ntrigs)
elog(ERROR, "too many trigger records found for relation \"%s\"",
RelationGetRelationName(relation));
build = &(triggers[found]);
if (numtrigs >= maxtrigs)
{
maxtrigs *= 2;
triggers = (Trigger *) repalloc(triggers, maxtrigs * sizeof(Trigger));
}
build = &(triggers[numtrigs]);
build->tgoid = HeapTupleGetOid(htup);
build->tgname = DatumGetCString(DirectFunctionCall1(nameout,
@ -1199,7 +1182,6 @@ RelationBuildTriggers(Relation relation)
bytea *val;
bool isnull;
char *p;
int i;
val = DatumGetByteaP(fastgetattr(htup,
Anum_pg_trigger_tgargs,
@ -1218,23 +1200,25 @@ RelationBuildTriggers(Relation relation)
else
build->tgargs = NULL;
found++;
numtrigs++;
}
systable_endscan(tgscan);
heap_close(tgrel, AccessShareLock);
if (found != ntrigs)
elog(ERROR, "%d trigger record(s) not found for relation \"%s\"",
ntrigs - found,
RelationGetRelationName(relation));
/* There might not be any triggers */
if (numtrigs == 0)
{
pfree(triggers);
return;
}
/* Build trigdesc */
trigdesc = (TriggerDesc *) palloc0(sizeof(TriggerDesc));
trigdesc->triggers = triggers;
trigdesc->numtriggers = ntrigs;
for (found = 0; found < ntrigs; found++)
InsertTrigger(trigdesc, &(triggers[found]), found);
trigdesc->numtriggers = numtrigs;
for (i = 0; i < numtrigs; i++)
InsertTrigger(trigdesc, &(triggers[i]), i);
/* Copy completed trigdesc into cache storage */
oldContext = MemoryContextSwitchTo(CacheMemoryContext);