trigger.c

PostgreSQL7.4.6 for Linux

				 * This trigger item hasn't been called yet. Check if we
				 * should call it now.
				 */
				if (immediate_only &&
				  deferredTriggerCheckState(event->dte_item[i].dti_tgoid,
											event->dte_item[i].dti_state))
				{
					still_deferred_ones = true;
					continue;
				}

				/*
				 * So let's fire it... but first, open the correct
				 * relation if this is not the same relation as before.
				 */
				if (rel == NULL || rel->rd_id != event->dte_relid)
				{
					if (rel)
						heap_close(rel, NoLock);
					FreeTriggerDesc(trigdesc);
					if (finfo)
						pfree(finfo);

					/*
					 * We assume that an appropriate lock is still held by
					 * the executor, so grab no new lock here.
					 */
					rel = heap_open(event->dte_relid, NoLock);

					/*
					 * Copy relation's trigger info so that we have a
					 * stable copy no matter what the called triggers do.
					 */
					trigdesc = CopyTriggerDesc(rel->trigdesc);

					if (trigdesc == NULL)		/* should not happen */
						elog(ERROR, "relation %u has no triggers",
							 event->dte_relid);

					/*
					 * Allocate space to cache fmgr lookup info for
					 * triggers.
					 */
					finfo = (FmgrInfo *)
						palloc0(trigdesc->numtriggers * sizeof(FmgrInfo));
				}

				DeferredTriggerExecute(event, i, rel, trigdesc, finfo,
									   per_tuple_context);

				event->dte_item[i].dti_state |= TRIGGER_DEFERRED_DONE;
			}					/* end loop over items within event */
		}

		/*
		 * If it's now completely done, throw it away.
		 *
		 * NB: it's possible the trigger calls above added more events to the
		 * queue, or that calls we will do later will want to add more, so
		 * we have to be careful about maintaining list validity here.
		 */
		next_event = event->dte_next;

		if (still_deferred_ones)
		{
			/* Not done, keep in list */
			prev_event = event;
		}
		else
		{
			/* Done */
			if (immediate_only)
			{
				/* delink it from list and free it */
				if (prev_event)
					prev_event->dte_next = next_event;
				else
					deferredTriggers->deftrig_events = next_event;
				pfree(event);
			}
			else
			{
				/*
				 * We will clean up later, but just for paranoia's sake,
				 * mark the event done.
				 */
				event->dte_event |= TRIGGER_DEFERRED_DONE;
			}
		}

		event = next_event;
	}

	/* Update list tail pointer in case we just deleted tail event */
	deferredTriggers->deftrig_event_tail = prev_event;

	/* Set the immediate event pointer for next time */
	deferredTriggers->deftrig_events_imm = prev_event;

	/* Release working resources */
	if (rel)
		heap_close(rel, NoLock);
	FreeTriggerDesc(trigdesc);
	if (finfo)
		pfree(finfo);
	MemoryContextDelete(per_tuple_context);
}


/* ----------
 * DeferredTriggerInit()
 *
 *	Initialize the deferred trigger mechanism. This is called during
 *	backend startup and is guaranteed to be before the first of all
 *	transactions.
 * ----------
 */
void
DeferredTriggerInit(void)
{
	/* Nothing to do */
	;
}


/* ----------
 * DeferredTriggerBeginXact()
 *
 *	Called at transaction start (either BEGIN or implicit for single
 *	statement outside of transaction block).
 * ----------
 */
void
DeferredTriggerBeginXact(void)
{
	/*
	 * This will be changed to a special context when the nested
	 * transactions project moves forward.
	 */
	MemoryContext cxt = TopTransactionContext;

	deferredTriggers = (DeferredTriggers) MemoryContextAlloc(TopTransactionContext,
										   sizeof(DeferredTriggersData));

	/*
	 * Create the per transaction memory context
	 */
	deferredTriggers->deftrig_cxt = AllocSetContextCreate(cxt,
												   "DeferredTriggerXact",
												ALLOCSET_DEFAULT_MINSIZE,
											   ALLOCSET_DEFAULT_INITSIZE,
											   ALLOCSET_DEFAULT_MAXSIZE);

	/*
	 * If unspecified, constraints default to IMMEDIATE, per SQL
	 */
	deferredTriggers->deftrig_all_isdeferred = false;
	deferredTriggers->deftrig_all_isset = false;

	deferredTriggers->deftrig_trigstates = NIL;
	deferredTriggers->deftrig_events = NULL;
	deferredTriggers->deftrig_events_imm = NULL;
	deferredTriggers->deftrig_event_tail = NULL;
}


/* ----------
 * DeferredTriggerEndQuery()
 *
 *	Called after one query sent down by the user has completely been
 *	processed. At this time we invoke all outstanding IMMEDIATE triggers.
 * ----------
 */
void
DeferredTriggerEndQuery(void)
{
	/*
	 * Ignore call if we aren't in a transaction.
	 */
	if (deferredTriggers == NULL)
		return;

	deferredTriggerInvokeEvents(true);
}


/* ----------
 * DeferredTriggerEndXact()
 *
 *	Called just before the current transaction is committed. At this
 *	time we invoke all DEFERRED triggers and tidy up.
 * ----------
 */
void
DeferredTriggerEndXact(void)
{
	/*
	 * Ignore call if we aren't in a transaction.
	 */
	if (deferredTriggers == NULL)
		return;

	deferredTriggerInvokeEvents(false);

	deferredTriggers = NULL;
}


/* ----------
 * DeferredTriggerAbortXact()
 *
 *	The current transaction has entered the abort state.
 *	All outstanding triggers are canceled so we simply throw
 *	away anything we know.
 * ----------
 */
void
DeferredTriggerAbortXact(void)
{
	/*
	 * Ignore call if we aren't in a transaction.
	 */
	if (deferredTriggers == NULL)
		return;

	/*
	 * Forget everything we know about deferred triggers.
	 */
	deferredTriggers = NULL;
}


/* ----------
 * DeferredTriggerSetState()
 *
 *	Called for the SET CONSTRAINTS ... utility command.
 * ----------
 */
void
DeferredTriggerSetState(ConstraintsSetStmt *stmt)
{
	List	   *l;

	/*
	 * Ignore call if we aren't in a transaction.
	 */
	if (deferredTriggers == NULL)
		return;

	/*
	 * Handle SET CONSTRAINTS ALL ...
	 */
	if (stmt->constraints == NIL)
	{
		/*
		 * Drop all per-transaction information about individual trigger
		 * states.
		 */
		l = deferredTriggers->deftrig_trigstates;
		while (l != NIL)
		{
			List	   *next = lnext(l);

			pfree(lfirst(l));
			pfree(l);
			l = next;
		}
		deferredTriggers->deftrig_trigstates = NIL;

		/*
		 * Set the per-transaction ALL state to known.
		 */
		deferredTriggers->deftrig_all_isset = true;
		deferredTriggers->deftrig_all_isdeferred = stmt->deferred;
	}
	else
	{
		Relation	tgrel;
		MemoryContext oldcxt;
		bool		found;
		DeferredTriggerStatus state;
		List	   *ls;
		List	   *loid = NIL;

		/* ----------
		 * Handle SET CONSTRAINTS constraint-name [, ...]
		 * First lookup all trigger Oid's for the constraint names.
		 * ----------
		 */
		tgrel = heap_openr(TriggerRelationName, AccessShareLock);

		foreach(l, stmt->constraints)
		{
			char	   *cname = strVal(lfirst(l));
			ScanKeyData skey;
			SysScanDesc tgscan;
			HeapTuple	htup;

			/*
			 * Check that only named constraints are set explicitly
			 */
			if (strlen(cname) == 0)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_NAME),
				errmsg("unnamed constraints cannot be set explicitly")));

			/*
			 * Setup to scan pg_trigger by tgconstrname ...
			 */
			ScanKeyEntryInitialize(&skey, (bits16) 0x0,
							   (AttrNumber) Anum_pg_trigger_tgconstrname,
								   (RegProcedure) F_NAMEEQ,
								   PointerGetDatum(cname));

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

			/*
			 * ... and search for the constraint trigger row
			 */
			found = false;

			while (HeapTupleIsValid(htup = systable_getnext(tgscan)))
			{
				Form_pg_trigger pg_trigger = (Form_pg_trigger) GETSTRUCT(htup);
				Oid			constr_oid;

				/*
				 * If we found some, check that they fit the deferrability
				 * but skip ON <event> RESTRICT ones, since they are
				 * silently never deferrable.
				 */
				if (stmt->deferred && !pg_trigger->tgdeferrable &&
					pg_trigger->tgfoid != F_RI_FKEY_RESTRICT_UPD &&
					pg_trigger->tgfoid != F_RI_FKEY_RESTRICT_DEL)
					ereport(ERROR,
							(errcode(ERRCODE_WRONG_OBJECT_TYPE),
							 errmsg("constraint \"%s\" is not deferrable",
									cname)));

				constr_oid = HeapTupleGetOid(htup);
				loid = lappendo(loid, constr_oid);
				found = true;
			}

			systable_endscan(tgscan);

			/*
			 * Not found ?
			 */
			if (!found)
				ereport(ERROR,
						(errcode(ERRCODE_UNDEFINED_OBJECT),
					 errmsg("constraint \"%s\" does not exist", cname)));
		}
		heap_close(tgrel, AccessShareLock);

		/*
		 * Inside of a transaction block set the trigger states of
		 * individual triggers on transaction level.
		 */
		oldcxt = MemoryContextSwitchTo(deferredTriggers->deftrig_cxt);

		foreach(l, loid)
		{
			found = false;
			foreach(ls, deferredTriggers->deftrig_trigstates)
			{
				state = (DeferredTriggerStatus) lfirst(ls);
				if (state->dts_tgoid == lfirsto(l))
				{
					state->dts_tgisdeferred = stmt->deferred;
					found = true;
					break;
				}
			}
			if (!found)
			{
				state = (DeferredTriggerStatus)
					palloc(sizeof(DeferredTriggerStatusData));
				state->dts_tgoid = lfirsto(l);
				state->dts_tgisdeferred = stmt->deferred;

				deferredTriggers->deftrig_trigstates =
					lappend(deferredTriggers->deftrig_trigstates, state);
			}
		}

		MemoryContextSwitchTo(oldcxt);
	}

	/*
	 * SQL99 requires that when a constraint is set to IMMEDIATE, any
	 * deferred checks against that constraint must be made when the SET
	 * CONSTRAINTS command is executed -- i.e. the effects of the SET
	 * CONSTRAINTS command applies retroactively. This happens "for free"
	 * since we have already made the necessary modifications to the
	 * constraints, and deferredTriggerEndQuery() is called by
	 * finish_xact_command().  But we must reset
	 * deferredTriggerInvokeEvents' tail pointer to make it rescan the
	 * entire list, in case some deferred events are now immediately
	 * invokable.
	 */
	deferredTriggers->deftrig_events_imm = NULL;
}


/* ----------
 * DeferredTriggerSaveEvent()
 *
 *	Called by ExecAR...Triggers() to add the event to the queue.
 *
 *	NOTE: should be called only if we've determined that an event must
 *	be added to the queue.
 * ----------
 */
static void
DeferredTriggerSaveEvent(ResultRelInfo *relinfo, int event, bool row_trigger,
						 HeapTuple oldtup, HeapTuple newtup)
{
	Relation	rel = relinfo->ri_RelationDesc;
	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
	MemoryContext oldcxt;
	DeferredTriggerEvent new_event;
	int			new_size;
	int			i;
	int			ntriggers;
	int			n_enabled_triggers = 0;
	int		   *tgindx;
	ItemPointerData oldctid;
	ItemPointerData newctid;

	if (deferredTriggers == NULL)
		elog(ERROR, "DeferredTriggerSaveEvent() called outside of transaction");

	/*
	 * Get the CTID's of OLD and NEW
	 */
	if (oldtup != NULL)
		ItemPointerCopy(&(oldtup->t_self), &(oldctid));
	else
		ItemPointerSetInvalid(&(oldctid));
	if (newtup != NULL)
		ItemPointerCopy(&(newtup->t_self), &(newctid));
	else
		ItemPointerSetInvalid(&(newctid));

	if (row_trigger)
	{
		ntriggers = trigdesc->n_after_row[event];
		tgindx = trigdesc->tg_after_row[event];
	}
	else
	{
		ntriggers = trigdesc->n_after_statement[event];
		tgindx = trigdesc->tg_after_statement[event];
	}

	/*
	 * Count the number of triggers that are actually enabled. Since we
	 * only add enabled triggers to the queue, we only need allocate
	 * enough space to hold them (and not any disabled triggers that may
	 * be associated with the relation).
	 */
	for (i = 0; i < ntriggers; i++)
	{
		Trigger    *trigger = &trigdesc->triggers[tgindx[i]];

		if (trigger->tgenabled)
			n_enabled_triggers++;
	}

	/*
	 * If all the triggers on this relation are disabled, we're done.
	 */
	if (n_enabled_triggers == 0)
		return;

	/*
	 * Create a new event
	 */
	oldcxt = MemoryContextSwitchTo(deferredTriggers->deftrig_cxt);

	new_size = offsetof(DeferredTriggerEventData, dte_item[0]) +
		n_enabled_triggers * sizeof(DeferredTriggerEventItem);

	new_event =