trigger.c

PostgreSQL7.4.6 for Linux

		DeferredTriggerSaveEvent(relinfo, TRIGGER_EVENT_UPDATE,
								 false, NULL, NULL);
}

HeapTuple
ExecBRUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
					 ItemPointer tupleid, HeapTuple newtuple,
					 CommandId cid)
{
	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
	int			ntrigs = trigdesc->n_before_row[TRIGGER_EVENT_UPDATE];
	int		   *tgindx = trigdesc->tg_before_row[TRIGGER_EVENT_UPDATE];
	TriggerData LocTriggerData;
	HeapTuple	trigtuple;
	HeapTuple	oldtuple;
	HeapTuple	intuple = newtuple;
	TupleTableSlot *newSlot;
	int			i;

	trigtuple = GetTupleForTrigger(estate, relinfo, tupleid, cid, &newSlot);
	if (trigtuple == NULL)
		return NULL;

	/*
	 * In READ COMMITTED isolation level it's possible that newtuple was
	 * changed due to concurrent update.
	 */
	if (newSlot != NULL)
		intuple = newtuple = ExecRemoveJunk(estate->es_junkFilter, newSlot);

	/* Allocate cache space for fmgr lookup info, if not done yet */
	if (relinfo->ri_TrigFunctions == NULL)
		relinfo->ri_TrigFunctions = (FmgrInfo *)
			palloc0(trigdesc->numtriggers * sizeof(FmgrInfo));

	LocTriggerData.type = T_TriggerData;
	LocTriggerData.tg_event = TRIGGER_EVENT_UPDATE |
		TRIGGER_EVENT_ROW |
		TRIGGER_EVENT_BEFORE;
	LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
	for (i = 0; i < ntrigs; i++)
	{
		Trigger    *trigger = &trigdesc->triggers[tgindx[i]];

		if (!trigger->tgenabled)
			continue;
		LocTriggerData.tg_trigtuple = trigtuple;
		LocTriggerData.tg_newtuple = oldtuple = newtuple;
		LocTriggerData.tg_trigger = trigger;
		newtuple = ExecCallTriggerFunc(&LocTriggerData,
								   relinfo->ri_TrigFunctions + tgindx[i],
									   GetPerTupleMemoryContext(estate));
		if (oldtuple != newtuple && oldtuple != intuple)
			heap_freetuple(oldtuple);
		if (newtuple == NULL)
			break;
	}
	heap_freetuple(trigtuple);
	return newtuple;
}

void
ExecARUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
					 ItemPointer tupleid, HeapTuple newtuple)
{
	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;

	if (trigdesc && trigdesc->n_after_row[TRIGGER_EVENT_UPDATE] > 0)
	{
		HeapTuple	trigtuple = GetTupleForTrigger(estate, relinfo,
												   tupleid,
												   (CommandId) 0,
												   NULL);

		DeferredTriggerSaveEvent(relinfo, TRIGGER_EVENT_UPDATE,
								 true, trigtuple, newtuple);
		heap_freetuple(trigtuple);
	}
}


static HeapTuple
GetTupleForTrigger(EState *estate, ResultRelInfo *relinfo,
				   ItemPointer tid, CommandId cid,
				   TupleTableSlot **newSlot)
{
	Relation	relation = relinfo->ri_RelationDesc;
	HeapTupleData tuple;
	HeapTuple	result;
	Buffer		buffer;

	if (newSlot != NULL)
	{
		int			test;

		/*
		 * mark tuple for update
		 */
		*newSlot = NULL;
		tuple.t_self = *tid;
ltrmark:;
		test = heap_mark4update(relation, &tuple, &buffer, cid);
		switch (test)
		{
			case HeapTupleSelfUpdated:
				/* treat it as deleted; do not process */
				ReleaseBuffer(buffer);
				return NULL;

			case HeapTupleMayBeUpdated:
				break;

			case HeapTupleUpdated:
				ReleaseBuffer(buffer);
				if (XactIsoLevel == XACT_SERIALIZABLE)
					ereport(ERROR,
							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
							 errmsg("could not serialize access due to concurrent update")));
				else if (!(ItemPointerEquals(&(tuple.t_self), tid)))
				{
					TupleTableSlot *epqslot = EvalPlanQual(estate,
											 relinfo->ri_RangeTableIndex,
														&(tuple.t_self));

					if (!(TupIsNull(epqslot)))
					{
						*tid = tuple.t_self;
						*newSlot = epqslot;
						goto ltrmark;
					}
				}

				/*
				 * if tuple was deleted or PlanQual failed for updated
				 * tuple - we have not process this tuple!
				 */
				return NULL;

			default:
				ReleaseBuffer(buffer);
				elog(ERROR, "unrecognized heap_mark4update status: %u",
					 test);
				return NULL;	/* keep compiler quiet */
		}
	}
	else
	{
		PageHeader	dp;
		ItemId		lp;

		buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));

		if (!BufferIsValid(buffer))
			elog(ERROR, "ReadBuffer failed");

		dp = (PageHeader) BufferGetPage(buffer);
		lp = PageGetItemId(dp, ItemPointerGetOffsetNumber(tid));

		Assert(ItemIdIsUsed(lp));

		tuple.t_datamcxt = NULL;
		tuple.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
		tuple.t_len = ItemIdGetLength(lp);
		tuple.t_self = *tid;
	}

	result = heap_copytuple(&tuple);
	ReleaseBuffer(buffer);

	return result;
}


/* ----------
 * Deferred trigger stuff
 * ----------
 */

typedef struct DeferredTriggersData
{
	/* Internal data is held in a per-transaction memory context */
	MemoryContext deftrig_cxt;
	/* ALL DEFERRED or ALL IMMEDIATE */
	bool		deftrig_all_isset;
	bool		deftrig_all_isdeferred;
	/* Per trigger state */
	List	   *deftrig_trigstates;
	/* List of pending deferred triggers. Previous comment below */
	DeferredTriggerEvent deftrig_events;
	DeferredTriggerEvent deftrig_events_imm;
	DeferredTriggerEvent deftrig_event_tail;
} DeferredTriggersData;

/* ----------
 * deftrig_events, deftrig_event_tail:
 * The list of pending deferred trigger events during the current transaction.
 *
 * deftrig_events is the head, deftrig_event_tail is the last entry.
 * Because this can grow pretty large, we don't use separate List nodes,
 * but instead thread the list through the dte_next fields of the member
 * nodes.  Saves just a few bytes per entry, but that adds up.
 *
 * deftrig_events_imm holds the tail pointer as of the last
 * deferredTriggerInvokeEvents call; we can use this to avoid rescanning
 * entries unnecessarily.  It is NULL if deferredTriggerInvokeEvents
 * hasn't run since the last state change.
 *
 * XXX Need to be able to shove this data out to a file if it grows too
 *	   large...
 * ----------
 */

typedef DeferredTriggersData *DeferredTriggers;

static DeferredTriggers deferredTriggers;

/* ----------
 * deferredTriggerCheckState()
 *
 *	Returns true if the trigger identified by tgoid is actually
 *	in state DEFERRED.
 * ----------
 */
static bool
deferredTriggerCheckState(Oid tgoid, int32 itemstate)
{
	MemoryContext oldcxt;
	List	   *sl;
	DeferredTriggerStatus trigstate;

	/*
	 * Not deferrable triggers (i.e. normal AFTER ROW triggers and
	 * constraints declared NOT DEFERRABLE, the state is always false.
	 */
	if ((itemstate & TRIGGER_DEFERRED_DEFERRABLE) == 0)
		return false;

	/*
	 * Lookup if we know an individual state for this trigger
	 */
	foreach(sl, deferredTriggers->deftrig_trigstates)
	{
		trigstate = (DeferredTriggerStatus) lfirst(sl);
		if (trigstate->dts_tgoid == tgoid)
			return trigstate->dts_tgisdeferred;
	}

	/*
	 * No individual state known - so if the user issued a SET CONSTRAINT
	 * ALL ..., we return that instead of the triggers default state.
	 */
	if (deferredTriggers->deftrig_all_isset)
		return deferredTriggers->deftrig_all_isdeferred;

	/*
	 * No ALL state known either, remember the default state as the
	 * current and return that.
	 */
	oldcxt = MemoryContextSwitchTo(deferredTriggers->deftrig_cxt);

	trigstate = (DeferredTriggerStatus)
		palloc(sizeof(DeferredTriggerStatusData));
	trigstate->dts_tgoid = tgoid;
	trigstate->dts_tgisdeferred =
		((itemstate & TRIGGER_DEFERRED_INITDEFERRED) != 0);
	deferredTriggers->deftrig_trigstates =
		lappend(deferredTriggers->deftrig_trigstates, trigstate);

	MemoryContextSwitchTo(oldcxt);

	return trigstate->dts_tgisdeferred;
}


/* ----------
 * deferredTriggerAddEvent()
 *
 *	Add a new trigger event to the queue.
 * ----------
 */
static void
deferredTriggerAddEvent(DeferredTriggerEvent event)
{
	/*
	 * Since the event list could grow quite long, we keep track of the
	 * list tail and append there, rather than just doing a stupid
	 * "lappend". This avoids O(N^2) behavior for large numbers of events.
	 */
	event->dte_next = NULL;
	if (deferredTriggers->deftrig_event_tail == NULL)
	{
		/* first list entry */
		deferredTriggers->deftrig_events = event;
		deferredTriggers->deftrig_event_tail = event;
	}
	else
	{
		deferredTriggers->deftrig_event_tail->dte_next = event;
		deferredTriggers->deftrig_event_tail = event;
	}
}


/* ----------
 * DeferredTriggerExecute()
 *
 *	Fetch the required tuples back from the heap and fire one
 *	single trigger function.
 *
 *	Frequently, this will be fired many times in a row for triggers of
 *	a single relation.	Therefore, we cache the open relation and provide
 *	fmgr lookup cache space at the caller level.
 *
 *	event: event currently being fired.
 *	itemno: item within event currently being fired.
 *	rel: open relation for event.
 *	trigdesc: working copy of rel's trigger info.
 *	finfo: array of fmgr lookup cache entries (one per trigger in trigdesc).
 *	per_tuple_context: memory context to call trigger function in.
 * ----------
 */
static void
DeferredTriggerExecute(DeferredTriggerEvent event, int itemno,
					Relation rel, TriggerDesc *trigdesc, FmgrInfo *finfo,
					   MemoryContext per_tuple_context)
{
	Oid			tgoid = event->dte_item[itemno].dti_tgoid;
	TriggerData LocTriggerData;
	HeapTupleData oldtuple;
	HeapTupleData newtuple;
	HeapTuple	rettuple;
	Buffer		oldbuffer;
	Buffer		newbuffer;
	int			tgindx;

	/*
	 * Fetch the required OLD and NEW tuples.
	 */
	if (ItemPointerIsValid(&(event->dte_oldctid)))
	{
		ItemPointerCopy(&(event->dte_oldctid), &(oldtuple.t_self));
		if (!heap_fetch(rel, SnapshotAny, &oldtuple, &oldbuffer, false, NULL))
			elog(ERROR, "failed to fetch old tuple for deferred trigger");
	}

	if (ItemPointerIsValid(&(event->dte_newctid)))
	{
		ItemPointerCopy(&(event->dte_newctid), &(newtuple.t_self));
		if (!heap_fetch(rel, SnapshotAny, &newtuple, &newbuffer, false, NULL))
			elog(ERROR, "failed to fetch new tuple for deferred trigger");
	}

	/*
	 * Setup the trigger information
	 */
	LocTriggerData.type = T_TriggerData;
	LocTriggerData.tg_event = (event->dte_event & TRIGGER_EVENT_OPMASK) |
		(event->dte_event & TRIGGER_EVENT_ROW);
	LocTriggerData.tg_relation = rel;

	LocTriggerData.tg_trigger = NULL;
	for (tgindx = 0; tgindx < trigdesc->numtriggers; tgindx++)
	{
		if (trigdesc->triggers[tgindx].tgoid == tgoid)
		{
			LocTriggerData.tg_trigger = &(trigdesc->triggers[tgindx]);
			break;
		}
	}
	if (LocTriggerData.tg_trigger == NULL)
		elog(ERROR, "could not find trigger %u", tgoid);

	switch (event->dte_event & TRIGGER_EVENT_OPMASK)
	{
		case TRIGGER_EVENT_INSERT:
			LocTriggerData.tg_trigtuple = &newtuple;
			LocTriggerData.tg_newtuple = NULL;
			break;

		case TRIGGER_EVENT_UPDATE:
			LocTriggerData.tg_trigtuple = &oldtuple;
			LocTriggerData.tg_newtuple = &newtuple;
			break;

		case TRIGGER_EVENT_DELETE:
			LocTriggerData.tg_trigtuple = &oldtuple;
			LocTriggerData.tg_newtuple = NULL;
			break;
	}

	/*
	 * Call the trigger and throw away any eventually returned updated
	 * tuple.
	 */
	rettuple = ExecCallTriggerFunc(&LocTriggerData,
								   finfo + tgindx,
								   per_tuple_context);
	if (rettuple != NULL && rettuple != &oldtuple && rettuple != &newtuple)
		heap_freetuple(rettuple);

	/*
	 * Release buffers
	 */
	if (ItemPointerIsValid(&(event->dte_oldctid)))
		ReleaseBuffer(oldbuffer);
	if (ItemPointerIsValid(&(event->dte_newctid)))
		ReleaseBuffer(newbuffer);
}


/* ----------
 * deferredTriggerInvokeEvents()
 *
 *	Scan the event queue for not yet invoked triggers. Check if they
 *	should be invoked now and do so.
 * ----------
 */
static void
deferredTriggerInvokeEvents(bool immediate_only)
{
	DeferredTriggerEvent event,
				prev_event;
	MemoryContext per_tuple_context;
	Relation	rel = NULL;
	TriggerDesc *trigdesc = NULL;
	FmgrInfo   *finfo = NULL;

	/*
	 * If immediate_only is true, we remove fully-processed events from
	 * the event queue to recycle space.  If immediate_only is false, we
	 * are going to discard the whole event queue on return anyway, so no
	 * need to bother with "retail" pfree's.
	 *
	 * If immediate_only is true, we need only scan from where the end of the
	 * queue was at the previous deferredTriggerInvokeEvents call; any
	 * non-deferred events before that point are already fired. (But if
	 * the deferral state changes, we must reset the saved position to the
	 * beginning of the queue, so as to process all events once with the
	 * new states.	See DeferredTriggerSetState.)
	 */

	/* Make a per-tuple memory context for trigger function calls */
	per_tuple_context =
		AllocSetContextCreate(CurrentMemoryContext,
							  "DeferredTriggerTupleContext",
							  ALLOCSET_DEFAULT_MINSIZE,
							  ALLOCSET_DEFAULT_INITSIZE,
							  ALLOCSET_DEFAULT_MAXSIZE);

	/*
	 * If immediate_only is true, then the only events that could need
	 * firing are those since deftrig_events_imm.  (But if
	 * deftrig_events_imm is NULL, we must scan the entire list.)
	 */
	if (immediate_only && deferredTriggers->deftrig_events_imm != NULL)
	{
		prev_event = deferredTriggers->deftrig_events_imm;
		event = prev_event->dte_next;
	}
	else
	{
		prev_event = NULL;
		event = deferredTriggers->deftrig_events;
	}

	while (event != NULL)
	{
		bool		still_deferred_ones = false;
		DeferredTriggerEvent next_event;
		int			i;

		/*
		 * Check if event is already completely done.
		 */
		if (!(event->dte_event & (TRIGGER_DEFERRED_DONE |
								  TRIGGER_DEFERRED_CANCELED)))
		{
			MemoryContextReset(per_tuple_context);

			/*
			 * Check each trigger item in the event.
			 */
			for (i = 0; i < event->dte_n_items; i++)
			{
				if (event->dte_item[i].dti_state & TRIGGER_DEFERRED_DONE)
					continue;

				/*