trigger.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

				CStringGetDatum(trigname));

	tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
								SnapshotNow, 2, skey);

	tup = systable_getnext(tgscan);

	if (!HeapTupleIsValid(tup))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("trigger \"%s\" for table \"%s\" does not exist",
						trigname, get_rel_name(relid))));

	if (!pg_class_ownercheck(relid, GetUserId()))
		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
					   get_rel_name(relid));

	object.classId = TriggerRelationId;
	object.objectId = HeapTupleGetOid(tup);
	object.objectSubId = 0;

	systable_endscan(tgscan);
	heap_close(tgrel, AccessShareLock);

	/*
	 * Do the deletion
	 */
	performDeletion(&object, behavior);
}

/*
 * Guts of trigger deletion.
 */
void
RemoveTriggerById(Oid trigOid)
{
	Relation	tgrel;
	SysScanDesc tgscan;
	ScanKeyData skey[1];
	HeapTuple	tup;
	Oid			relid;
	Relation	rel;
	Relation	pgrel;
	HeapTuple	tuple;
	Form_pg_class classForm;

	tgrel = heap_open(TriggerRelationId, RowExclusiveLock);

	/*
	 * Find the trigger to delete.
	 */
	ScanKeyInit(&skey[0],
				ObjectIdAttributeNumber,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(trigOid));

	tgscan = systable_beginscan(tgrel, TriggerOidIndexId, true,
								SnapshotNow, 1, skey);

	tup = systable_getnext(tgscan);
	if (!HeapTupleIsValid(tup))
		elog(ERROR, "could not find tuple for trigger %u", trigOid);

	/*
	 * Open and exclusive-lock the relation the trigger belongs to.
	 */
	relid = ((Form_pg_trigger) GETSTRUCT(tup))->tgrelid;

	rel = heap_open(relid, AccessExclusiveLock);

	if (rel->rd_rel->relkind != RELKIND_RELATION)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not a table",
						RelationGetRelationName(rel))));

	if (!allowSystemTableMods && IsSystemRelation(rel))
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission denied: \"%s\" is a system catalog",
						RelationGetRelationName(rel))));

	/*
	 * Delete the pg_trigger tuple.
	 */
	simple_heap_delete(tgrel, &tup->t_self);

	systable_endscan(tgscan);
	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.
	 */
	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);

	/* Keep lock on trigger's rel until end of xact */
	heap_close(rel, NoLock);
}

/*
 *		renametrig		- changes the name of a trigger on a relation
 *
 *		trigger name is changed in trigger catalog.
 *		No record of the previous name is kept.
 *
 *		get proper relrelation from relation catalog (if not arg)
 *		scan trigger catalog
 *				for name conflict (within rel)
 *				for original trigger (if not arg)
 *		modify tgname in trigger tuple
 *		update row in catalog
 */
void
renametrig(Oid relid,
		   const char *oldname,
		   const char *newname)
{
	Relation	targetrel;
	Relation	tgrel;
	HeapTuple	tuple;
	SysScanDesc tgscan;
	ScanKeyData key[2];

	/*
	 * Grab an exclusive lock on the target table, which we will NOT release
	 * until end of transaction.
	 */
	targetrel = heap_open(relid, AccessExclusiveLock);

	/*
	 * Scan pg_trigger twice for existing triggers on relation.  We do this in
	 * order to ensure a trigger does not exist with newname (The unique index
	 * on tgrelid/tgname would complain anyway) and to ensure a trigger does
	 * exist with oldname.
	 *
	 * 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_open(TriggerRelationId, RowExclusiveLock);

	/*
	 * First pass -- look for name conflict
	 */
	ScanKeyInit(&key[0],
				Anum_pg_trigger_tgrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(relid));
	ScanKeyInit(&key[1],
				Anum_pg_trigger_tgname,
				BTEqualStrategyNumber, F_NAMEEQ,
				PointerGetDatum(newname));
	tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
								SnapshotNow, 2, key);
	if (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
		ereport(ERROR,
				(errcode(ERRCODE_DUPLICATE_OBJECT),
				 errmsg("trigger \"%s\" for relation \"%s\" already exists",
						newname, RelationGetRelationName(targetrel))));
	systable_endscan(tgscan);

	/*
	 * Second pass -- look for trigger existing with oldname and update
	 */
	ScanKeyInit(&key[0],
				Anum_pg_trigger_tgrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(relid));
	ScanKeyInit(&key[1],
				Anum_pg_trigger_tgname,
				BTEqualStrategyNumber, F_NAMEEQ,
				PointerGetDatum(oldname));
	tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
								SnapshotNow, 2, key);
	if (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
	{
		/*
		 * Update pg_trigger tuple with new tgname.
		 */
		tuple = heap_copytuple(tuple);	/* need a modifiable copy */

		namestrcpy(&((Form_pg_trigger) GETSTRUCT(tuple))->tgname, newname);

		simple_heap_update(tgrel, &tuple->t_self, tuple);

		/* keep system catalog indexes current */
		CatalogUpdateIndexes(tgrel, tuple);

		/*
		 * Invalidate relation's relcache entry so that other backends (and
		 * this one too!) are sent SI message to make them rebuild relcache
		 * entries.  (Ideally this should happen automatically...)
		 */
		CacheInvalidateRelcache(targetrel);
	}
	else
	{
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("trigger \"%s\" for table \"%s\" does not exist",
						oldname, RelationGetRelationName(targetrel))));
	}

	systable_endscan(tgscan);

	heap_close(tgrel, RowExclusiveLock);

	/*
	 * Close rel, but keep exclusive lock!
	 */
	heap_close(targetrel, NoLock);
}


/*
 * EnableDisableTrigger()
 *
 *	Called by ALTER TABLE ENABLE/DISABLE TRIGGER
 *	to change 'tgenabled' flag for the specified trigger(s)
 *
 * rel: relation to process (caller must hold suitable lock on it)
 * tgname: trigger to process, or NULL to scan all triggers
 * enable: new value for tgenabled flag
 * skip_system: if true, skip "system" triggers (constraint triggers)
 *
 * Caller should have checked permissions for the table; here we also
 * enforce that superuser privilege is required to alter the state of
 * system triggers
 */
void
EnableDisableTrigger(Relation rel, const char *tgname,
					 bool enable, bool skip_system)
{
	Relation	tgrel;
	int			nkeys;
	ScanKeyData keys[2];
	SysScanDesc tgscan;
	HeapTuple	tuple;
	bool		found;
	bool		changed;

	/* Scan the relevant entries in pg_triggers */
	tgrel = heap_open(TriggerRelationId, RowExclusiveLock);

	ScanKeyInit(&keys[0],
				Anum_pg_trigger_tgrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(rel)));
	if (tgname)
	{
		ScanKeyInit(&keys[1],
					Anum_pg_trigger_tgname,
					BTEqualStrategyNumber, F_NAMEEQ,
					CStringGetDatum(tgname));
		nkeys = 2;
	}
	else
		nkeys = 1;

	tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
								SnapshotNow, nkeys, keys);

	found = changed = false;

	while (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
	{
		Form_pg_trigger oldtrig = (Form_pg_trigger) GETSTRUCT(tuple);

		if (oldtrig->tgisconstraint)
		{
			/* system trigger ... ok to process? */
			if (skip_system)
				continue;
			if (!superuser())
				ereport(ERROR,
						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
					  errmsg("permission denied: \"%s\" is a system trigger",
							 NameStr(oldtrig->tgname))));
		}

		found = true;

		if (oldtrig->tgenabled != enable)
		{
			/* need to change this one ... make a copy to scribble on */
			HeapTuple	newtup = heap_copytuple(tuple);
			Form_pg_trigger newtrig = (Form_pg_trigger) GETSTRUCT(newtup);

			newtrig->tgenabled = enable;

			simple_heap_update(tgrel, &newtup->t_self, newtup);

			/* Keep catalog indexes current */
			CatalogUpdateIndexes(tgrel, newtup);

			heap_freetuple(newtup);

			changed = true;
		}
	}

	systable_endscan(tgscan);

	heap_close(tgrel, RowExclusiveLock);

	if (tgname && !found)
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("trigger \"%s\" for table \"%s\" does not exist",
						tgname, RelationGetRelationName(rel))));

	/*
	 * If we changed anything, broadcast a SI inval message to force each
	 * backend (including our own!) to rebuild relation's relcache entry.
	 * Otherwise they will fail to apply the change promptly.
	 */
	if (changed)
		CacheInvalidateRelcache(rel);
}


/*
 * Build trigger data to attach to the given relcache entry.
 *
 * Note that trigger data attached to a relcache entry must be stored in
 * CacheMemoryContext to ensure it survives as long as the relcache entry.
 * But we should be running in a less long-lived working context.  To avoid
 * leaking cache memory if this routine fails partway through, we build a
 * temporary TriggerDesc in working memory and then copy the completed
 * structure into cache memory.
 */
void
RelationBuildTriggers(Relation relation)
{
	TriggerDesc *trigdesc;
	int			ntrigs = relation->rd_rel->reltriggers;
	Trigger    *triggers;
	int			found = 0;
	Relation	tgrel;
	ScanKeyData skey;
	SysScanDesc tgscan;
	HeapTuple	htup;
	MemoryContext oldContext;

	Assert(ntrigs > 0);			/* else I should not have been called */

	triggers = (Trigger *) palloc(ntrigs * sizeof(Trigger));

	/*
	 * Note: since we scan the triggers using TriggerRelidNameIndexId, 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.
	 */
	ScanKeyInit(&skey,
				Anum_pg_trigger_tgrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(relation)));

	tgrel = heap_open(TriggerRelationId, AccessShareLock);
	tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
								SnapshotNow, 1, &skey);

	while (HeapTupleIsValid(htup = systable_getnext(tgscan)))
	{
		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]);

		build->tgoid = HeapTupleGetOid(htup);
		build->tgname = DatumGetCString(DirectFunctionCall1(nameout,
										 NameGetDatum(&pg_trigger->tgname)));
		build->tgfoid = pg_trigger->tgfoid;
		build->tgtype = pg_trigger->tgtype;
		build->tgenabled = pg_trigger->tgenabled;
		build->tgisconstraint = pg_trigger->tgisconstraint;
		build->tgconstrrelid = pg_trigger->tgconstrrelid;
		build->tgdeferrable = pg_trigger->tgdeferrable;
		build->tginitdeferred = pg_trigger->tginitdeferred;
		build->tgnargs = pg_trigger->tgnargs;
		/* tgattr is first var-width field, so OK to access directly */
		build->tgnattr = pg_trigger->tgattr.dim1;
		if (build->tgnattr > 0)
		{
			build->tgattr = (int2 *) palloc(build->tgnattr * sizeof(int2));
			memcpy(build->tgattr, &(pg_trigger->tgattr.values),
				   build->tgnattr * sizeof(int2));
		}
		else
			build->tgattr = NULL;
		if (build->tgnargs > 0)
		{
			bytea	   *val;
			bool		isnull;
			char	   *p;
			int			i;

			val = (bytea *)
				DatumGetPointer(fastgetattr(htup,
											Anum_pg_trigger_tgargs,
											tgrel->rd_att, &isnull));
			if (isnull)
				elog(ERROR, "tgargs is null in trigger for relation \"%s\"",
					 RelationGetRelationName(relation));
			p = (char *) VARDATA(val);
			build->tgargs = (char **) palloc(build->tgnargs * sizeof(char *));
			for (i = 0; i < build->tgnargs; i++)
			{
				build->tgargs[i] = pstrdup(p);
				p += strlen(p) + 1;
			}
		}
		else
			build->tgargs = NULL;

		found++;
	}

	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));

	/* Build trigdesc */
	trigdesc = (TriggerDesc *) palloc0(sizeof(TriggerDesc));
	trigdesc->triggers = triggers;
	trigdesc->numtriggers = ntrigs;
	for (found = 0; found < ntrigs; found++)
		InsertTrigger(trigdesc, &(triggers[found]), found);

	/* Copy completed trigdesc into cache storage */
	oldContext = MemoryContextSwitchTo(CacheMemoryContext);
	relation->trigdesc = CopyTriggerDesc(trigdesc);
	MemoryContextSwitchTo(oldContext);

	/* Release working memory */
	FreeTriggerDesc(trigdesc);
}

/*
 * Insert the given trigger into the appropriate index list(s) for it
 *
 * To simplify storage management, we allocate each index list at the max