trigger.c

PostgreSQL7.4.6 for Linux

					   get_rel_name(relid));

	object.classId = RelationGetRelid(tgrel);
	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_openr(TriggerRelationName, RowExclusiveLock);

	/*
	 * Find the trigger to delete.
	 */
	ScanKeyEntryInitialize(&skey[0], 0x0,
						   ObjectIdAttributeNumber, F_OIDEQ,
						   ObjectIdGetDatum(trigOid));

	tgscan = systable_beginscan(tgrel, TriggerOidIndex, 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_openr(RelationRelationName, 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_openr(TriggerRelationName, RowExclusiveLock);

	/*
	 * First pass -- look for name conflict
	 */
	ScanKeyEntryInitialize(&key[0], 0,
						   Anum_pg_trigger_tgrelid,
						   F_OIDEQ,
						   ObjectIdGetDatum(relid));
	ScanKeyEntryInitialize(&key[1], 0,
						   Anum_pg_trigger_tgname,
						   F_NAMEEQ,
						   PointerGetDatum(newname));
	tgscan = systable_beginscan(tgrel, TriggerRelidNameIndex, 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
	 */
	ScanKeyEntryInitialize(&key[0], 0,
						   Anum_pg_trigger_tgrelid,
						   F_OIDEQ,
						   ObjectIdGetDatum(relid));
	ScanKeyEntryInitialize(&key[1], 0,
						   Anum_pg_trigger_tgname,
						   F_NAMEEQ,
						   PointerGetDatum(oldname));
	tgscan = systable_beginscan(tgrel, TriggerRelidNameIndex, 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(relid);
	}
	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);
}

/*
 * 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 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,
						   (RegProcedure) F_OIDEQ,
						   ObjectIdGetDatum(RelationGetRelid(relation)));

	tgrel = heap_openr(TriggerRelationName, AccessShareLock);
	tgscan = systable_beginscan(tgrel, TriggerRelidNameIndex, 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;
		memcpy(build->tgattr, &(pg_trigger->tgattr),
			   FUNC_MAX_ARGS * sizeof(int16));
		if (build->tgnargs > 0)
		{
			bytea	   *val;
			bool		isnull;
			char	   *p;
			int			i;

			val = (bytea *) 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
 * possible size (trigdesc->numtriggers) if it's used at all.  This does
 * not waste space permanently since we're only building a temporary
 * trigdesc at this point.
 */
static void
InsertTrigger(TriggerDesc *trigdesc, Trigger *trigger, int indx)
{
	uint16	   *n;
	int		  **t,
			  **tp;

	if (TRIGGER_FOR_ROW(trigger->tgtype))
	{
		/* ROW trigger */
		if (TRIGGER_FOR_BEFORE(trigger->tgtype))
		{
			n = trigdesc->n_before_row;
			t = trigdesc->tg_before_row;
		}
		else
		{
			n = trigdesc->n_after_row;
			t = trigdesc->tg_after_row;
		}
	}
	else
	{
		/* STATEMENT trigger */
		if (TRIGGER_FOR_BEFORE(trigger->tgtype))
		{
			n = trigdesc->n_before_statement;
			t = trigdesc->tg_before_statement;
		}
		else
		{
			n = trigdesc->n_after_statement;
			t = trigdesc->tg_after_statement;
		}
	}

	if (TRIGGER_FOR_INSERT(trigger->tgtype))
	{
		tp = &(t[TRIGGER_EVENT_INSERT]);
		if (*tp == NULL)
			*tp = (int *) palloc(trigdesc->numtriggers * sizeof(int));
		(*tp)[n[TRIGGER_EVENT_INSERT]] = indx;
		(n[TRIGGER_EVENT_INSERT])++;
	}

	if (TRIGGER_FOR_DELETE(trigger->tgtype))
	{
		tp = &(t[TRIGGER_EVENT_DELETE]);
		if (*tp == NULL)
			*tp = (int *) palloc(trigdesc->numtriggers * sizeof(int));
		(*tp)[n[TRIGGER_EVENT_DELETE]] = indx;
		(n[TRIGGER_EVENT_DELETE])++;
	}

	if (TRIGGER_FOR_UPDATE(trigger->tgtype))
	{
		tp = &(t[TRIGGER_EVENT_UPDATE]);
		if (*tp == NULL)
			*tp = (int *) palloc(trigdesc->numtriggers * sizeof(int));
		(*tp)[n[TRIGGER_EVENT_UPDATE]] = indx;
		(n[TRIGGER_EVENT_UPDATE])++;
	}
}

/*
 * Copy a TriggerDesc data structure.
 *
 * The copy is allocated in the current memory context.
 */
TriggerDesc *
CopyTriggerDesc(TriggerDesc *trigdesc)
{
	TriggerDesc *newdesc;
	uint16	   *n;
	int		  **t,
			   *tnew;
	Trigger    *trigger;
	int			i;

	if (trigdesc == NULL || trigdesc->numtriggers <= 0)
		return NULL;

	newdesc = (TriggerDesc *) palloc(sizeof(TriggerDesc));
	memcpy(newdesc, trigdesc, sizeof(TriggerDesc));

	trigger = (Trigger *) palloc(trigdesc->numtriggers * sizeof(Trigger));
	memcpy(trigger, trigdesc->triggers,
		   trigdesc->numtriggers * sizeof(Trigger));
	newdesc->triggers = trigger;

	for (i = 0; i < trigdesc->numtriggers; i++)
	{
		trigger->tgname = pstrdup(trigger->tgname);
		if (trigger->tgnargs > 0)
		{
			char	  **newargs;
			int16		j;

			newargs = (char **) palloc(trigger->tgnargs * sizeof(char *));
			for (j = 0; j < trigger->tgnargs; j++)
				newargs[j] = pstrdup(trigger->tgargs[j]);
			trigger->tgargs = newargs;
		}
		trigger++;
	}

	n = newdesc->n_before_statement;
	t = newdesc->tg_before_statement;
	for (i = 0; i < TRIGGER_NUM_EVENT_CLASSES; i++)
	{
		if (n[i] > 0)
		{
			tnew = (int *) palloc(n[i] * sizeof(int));
			memcpy(tnew, t[i], n[i] * sizeof(int));
			t[i] = tnew;
		}
		else
			t[i] = NULL;
	}
	n = newdesc->n_before_row;
	t = newdesc->tg_before_row;
	for (i = 0; i < TRIGGER_NUM_EVENT_CLASSES; i++)
	{
		if (n[i] > 0)
		{
			tnew = (int *) palloc(n[i] * sizeof(int));
			memcpy(tnew, t[i], n[i] * sizeof(int));
			t[i] = tnew;
		}
		else
			t[i] = NULL;
	}
	n = newdesc->n_after_row;
	t = newdesc->tg_after_row;
	for (i = 0; i < TRIGGER_NUM_EVENT_CLASSES; i++)
	{
		if (n[i] > 0)
		{
			tnew = (int *) palloc(n[i] * sizeof(int));
			memcpy(tnew, t[i], n[i] * sizeof(int));
			t[i] = tnew;