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pg_trigger's index on tgrelid is replaced by a unique index on

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(tgrelid, tgname).  This provides an additional check on trigger name
uniqueness per-table (which was already enforced by the code anyway).
With this change, RelationBuildTriggers will read the triggers in
order by tgname, since it's scanning using this index.  Since a
predictable trigger ordering has been requested for some time, document
this behavior as a feature.  Also document that rules fire in name
order, since yesterday's changes to pg_rewrite indexing cause that too.
This commit is contained in:
Tom Lane
2002-04-19 16:36:08 +00:00
parent 87d00363cb
commit 201737168c
11 changed files with 230 additions and 172 deletions
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86
src/backend/commands/trigger.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.113 2002/04/12 20:38:24 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.114 2002/04/19 16:36:08 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -90,14 +90,15 @@ CreateTrigger(CreateTrigStmt *stmt)
elog(ERROR, "permission denied");
/*
* If trigger is a constraint, user trigger name as constraint name
* If trigger is an RI constraint, use trigger name as constraint name
* and build a unique trigger name instead.
*/
if (stmt->isconstraint)
{
constrname = stmt->trigname;
snprintf(constrtrigname, sizeof(constrtrigname),
"RI_ConstraintTrigger_%u", newoid());
stmt->trigname = constrtrigname;
sprintf(constrtrigname, "RI_ConstraintTrigger_%u", newoid());
if (stmt->constrrel != NULL)
constrrelid = RangeVarGetRelid(stmt->constrrel, false);
@ -139,15 +140,20 @@ CreateTrigger(CreateTrigStmt *stmt)
}
/*
* Scan pg_trigger for existing triggers on relation. NOTE that this
* is cool only because we have AccessExclusiveLock on the relation,
* so the trigger set won't be changing underneath us.
* 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.)
*
* NOTE that this is cool only because we have AccessExclusiveLock on the
* relation, so the trigger set won't be changing underneath us.
*/
tgrel = heap_openr(TriggerRelationName, RowExclusiveLock);
ScanKeyEntryInitialize(&key, 0, Anum_pg_trigger_tgrelid,
ScanKeyEntryInitialize(&key, 0,
Anum_pg_trigger_tgrelid,
F_OIDEQ,
ObjectIdGetDatum(RelationGetRelid(rel)));
tgscan = systable_beginscan(tgrel, TriggerRelidIndex, true,
tgscan = systable_beginscan(tgrel, TriggerRelidNameIndex, true,
SnapshotNow, 1, &key);
while (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
{
@ -336,15 +342,20 @@ DropTrigger(Oid relid, const char *trigname)
/*
* Search pg_trigger, delete target trigger, count remaining triggers
* for relation. 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.
* for relation. (Although we could fetch and delete the target
* trigger directly, we'd still have to scan the remaining triggers,
* so we may as well do both in one indexscan.)
*
* 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.
*/
tgrel = heap_openr(TriggerRelationName, RowExclusiveLock);
ScanKeyEntryInitialize(&key, 0, Anum_pg_trigger_tgrelid,
ScanKeyEntryInitialize(&key, 0,
Anum_pg_trigger_tgrelid,
F_OIDEQ,
ObjectIdGetDatum(relid));
tgscan = systable_beginscan(tgrel, TriggerRelidIndex, true,
tgscan = systable_beginscan(tgrel, TriggerRelidNameIndex, true,
SnapshotNow, 1, &key);
while (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
{
@ -409,10 +420,11 @@ RelationRemoveTriggers(Relation rel)
bool found = false;
tgrel = heap_openr(TriggerRelationName, RowExclusiveLock);
ScanKeyEntryInitialize(&key, 0, Anum_pg_trigger_tgrelid,
ScanKeyEntryInitialize(&key, 0,
Anum_pg_trigger_tgrelid,
F_OIDEQ,
ObjectIdGetDatum(RelationGetRelid(rel)));
tgscan = systable_beginscan(tgrel, TriggerRelidIndex, true,
tgscan = systable_beginscan(tgrel, TriggerRelidNameIndex, true,
SnapshotNow, 1, &key);
while (HeapTupleIsValid(tup = systable_getnext(tgscan)))
@ -462,7 +474,8 @@ RelationRemoveTriggers(Relation rel)
/*
* Also drop all constraint triggers referencing this relation
*/
ScanKeyEntryInitialize(&key, 0, Anum_pg_trigger_tgconstrrelid,
ScanKeyEntryInitialize(&key, 0,
Anum_pg_trigger_tgconstrrelid,
F_OIDEQ,
ObjectIdGetDatum(RelationGetRelid(rel)));
tgscan = systable_beginscan(tgrel, TriggerConstrRelidIndex, true,
@ -502,7 +515,7 @@ RelationBuildTriggers(Relation relation)
{
TriggerDesc *trigdesc;
int ntrigs = relation->rd_rel->reltriggers;
Trigger *triggers = NULL;
Trigger *triggers;
int found = 0;
Relation tgrel;
ScanKeyData skey;
@ -511,6 +524,15 @@ RelationBuildTriggers(Relation relation)
struct varlena *val;
bool isnull;
triggers = (Trigger *) MemoryContextAlloc(CacheMemoryContext,
ntrigs * sizeof(Trigger));
/*
* Note: since we scan the triggers using TriggerRelidNameIndex,
* we will be reading the triggers in name order, except possibly
* during emergency-recovery operations (ie, IsIgnoringSystemIndexes).
* This in turn ensures that triggers will be fired in name order.
*/
ScanKeyEntryInitialize(&skey,
(bits16) 0x0,
(AttrNumber) Anum_pg_trigger_tgrelid,
@ -518,7 +540,7 @@ RelationBuildTriggers(Relation relation)
ObjectIdGetDatum(RelationGetRelid(relation)));
tgrel = heap_openr(TriggerRelationName, AccessShareLock);
tgscan = systable_beginscan(tgrel, TriggerRelidIndex, true,
tgscan = systable_beginscan(tgrel, TriggerRelidNameIndex, true,
SnapshotNow, 1, &skey);
while (HeapTupleIsValid(htup = systable_getnext(tgscan)))
@ -526,16 +548,9 @@ RelationBuildTriggers(Relation relation)
Form_pg_trigger pg_trigger = (Form_pg_trigger) GETSTRUCT(htup);
Trigger *build;
if (found == ntrigs)
if (found >= ntrigs)
elog(ERROR, "RelationBuildTriggers: unexpected record found for rel %s",
RelationGetRelationName(relation));
if (triggers == NULL)
triggers = (Trigger *) MemoryContextAlloc(CacheMemoryContext,
sizeof(Trigger));
else
triggers = (Trigger *) repalloc(triggers,
(found + 1) * sizeof(Trigger));
build = &(triggers[found]);
build->tgoid = htup->t_data->t_oid;
@ -730,6 +745,9 @@ equalTriggerDescs(TriggerDesc *trigdesc1, TriggerDesc *trigdesc2)
* We need not examine the "index" data, just the trigger array
* itself; if we have the same triggers with the same types, the
* derived index data should match.
*
* As of 7.3 we assume trigger set ordering is significant in the
* comparison; so we just compare corresponding slots of the two sets.
*/
if (trigdesc1 != NULL)
{
@ -740,21 +758,9 @@ equalTriggerDescs(TriggerDesc *trigdesc1, TriggerDesc *trigdesc2)
for (i = 0; i < trigdesc1->numtriggers; i++)
{
Trigger *trig1 = trigdesc1->triggers + i;
Trigger *trig2 = NULL;
Trigger *trig2 = trigdesc2->triggers + i;
/*
* We can't assume that the triggers are always read from
* pg_trigger in the same order; so use the trigger OIDs to
* identify the triggers to compare. (We assume here that the
* same OID won't appear twice in either trigger set.)
*/
for (j = 0; j < trigdesc2->numtriggers; j++)
{
trig2 = trigdesc2->triggers + j;
if (trig1->tgoid == trig2->tgoid)
break;
}
if (j >= trigdesc2->numtriggers)
if (trig1->tgoid != trig2->tgoid)
return false;
if (strcmp(trig1->tgname, trig2->tgname) != 0)
return false;