trigger.c

PostgreSQL7.4.6 for Linux

/*-------------------------------------------------------------------------
 *
 * trigger.c
 *	  PostgreSQL TRIGGERs support code.
 *
 * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.159 2003/10/02 06:34:03 petere Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/catname.h"
#include "catalog/dependency.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_language.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_trigger.h"
#include "catalog/pg_type.h"
#include "commands/defrem.h"
#include "commands/trigger.h"
#include "executor/executor.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "parser/parse_func.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"


static void InsertTrigger(TriggerDesc *trigdesc, Trigger *trigger, int indx);
static HeapTuple GetTupleForTrigger(EState *estate,
				   ResultRelInfo *relinfo,
				   ItemPointer tid,
				   CommandId cid,
				   TupleTableSlot **newSlot);
static HeapTuple ExecCallTriggerFunc(TriggerData *trigdata,
					FmgrInfo *finfo,
					MemoryContext per_tuple_context);
static void DeferredTriggerSaveEvent(ResultRelInfo *relinfo, int event,
				   bool row_trigger, HeapTuple oldtup, HeapTuple newtup);
static void DeferredTriggerExecute(DeferredTriggerEvent event, int itemno,
					Relation rel, TriggerDesc *trigdesc, FmgrInfo *finfo,
					   MemoryContext per_tuple_context);


/*
 * Create a trigger.  Returns the OID of the created trigger.
 *
 * forConstraint, if true, says that this trigger is being created to
 * implement a constraint.	The caller will then be expected to make
 * a pg_depend entry linking the trigger to that constraint (and thereby
 * to the owning relation(s)).
 */
Oid
CreateTrigger(CreateTrigStmt *stmt, bool forConstraint)
{
	int16		tgtype;
	int16		tgattr[FUNC_MAX_ARGS];
	Datum		values[Natts_pg_trigger];
	char		nulls[Natts_pg_trigger];
	Relation	rel;
	AclResult	aclresult;
	Relation	tgrel;
	SysScanDesc tgscan;
	ScanKeyData key;
	Relation	pgrel;
	HeapTuple	tuple;
	Oid			fargtypes[FUNC_MAX_ARGS];
	Oid			funcoid;
	Oid			funcrettype;
	Oid			trigoid;
	int			found = 0;
	int			i;
	char		constrtrigname[NAMEDATALEN];
	char	   *trigname;
	char	   *constrname;
	Oid			constrrelid = InvalidOid;
	ObjectAddress myself,
				referenced;

	rel = heap_openrv(stmt->relation, AccessExclusiveLock);

	if (stmt->constrrel != NULL)
		constrrelid = RangeVarGetRelid(stmt->constrrel, false);
	else if (stmt->isconstraint)
	{
		/*
		 * If this trigger is a constraint (and a foreign key one) then we
		 * really need a constrrelid.  Since we don't have one, we'll try
		 * to generate one from the argument information.
		 *
		 * This is really just a workaround for a long-ago pg_dump bug that
		 * omitted the FROM clause in dumped CREATE CONSTRAINT TRIGGER
		 * commands.  We don't want to bomb out completely here if we
		 * can't determine the correct relation, because that would
		 * prevent loading the dump file.  Instead, NOTICE here and ERROR
		 * in the trigger.
		 */
		bool		needconstrrelid = false;
		void	   *elem = NULL;

		if (strncmp(strVal(llast(stmt->funcname)), "RI_FKey_check_", 14) == 0)
		{
			/* A trigger on FK table. */
			needconstrrelid = true;
			if (length(stmt->args) > RI_PK_RELNAME_ARGNO)
				elem = nth(RI_PK_RELNAME_ARGNO, stmt->args);
		}
		else if (strncmp(strVal(llast(stmt->funcname)), "RI_FKey_", 8) == 0)
		{
			/* A trigger on PK table. */
			needconstrrelid = true;
			if (length(stmt->args) > RI_FK_RELNAME_ARGNO)
				elem = nth(RI_FK_RELNAME_ARGNO, stmt->args);
		}
		if (elem != NULL)
		{
			RangeVar   *rel = makeRangeVar(NULL, strVal(elem));

			constrrelid = RangeVarGetRelid(rel, true);
		}
		if (needconstrrelid && constrrelid == InvalidOid)
			ereport(NOTICE,
					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
					 errmsg("could not determine referenced table for constraint \"%s\"",
							stmt->trigname)));
	}

	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))));

	/* permission checks */

	if (stmt->isconstraint)
	{
		/* foreign key constraint trigger */

		aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
									  ACL_REFERENCES);
		if (aclresult != ACLCHECK_OK)
			aclcheck_error(aclresult, ACL_KIND_CLASS,
						   RelationGetRelationName(rel));
		if (constrrelid != InvalidOid)
		{
			aclresult = pg_class_aclcheck(constrrelid, GetUserId(),
										  ACL_REFERENCES);
			if (aclresult != ACLCHECK_OK)
				aclcheck_error(aclresult, ACL_KIND_CLASS,
							   get_rel_name(constrrelid));
		}
	}
	else
	{
		/* real trigger */
		aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
									  ACL_TRIGGER);
		if (aclresult != ACLCHECK_OK)
			aclcheck_error(aclresult, ACL_KIND_CLASS,
						   RelationGetRelationName(rel));
	}

	/*
	 * Generate the trigger's OID now, so that we can use it in the name
	 * if needed.
	 */
	trigoid = newoid();

	/*
	 * If trigger is an RI constraint, use specified trigger name as
	 * constraint name and build a unique trigger name instead. This is
	 * mainly for backwards compatibility with CREATE CONSTRAINT TRIGGER
	 * commands.
	 */
	if (stmt->isconstraint)
	{
		snprintf(constrtrigname, sizeof(constrtrigname),
				 "RI_ConstraintTrigger_%u", trigoid);
		trigname = constrtrigname;
		constrname = stmt->trigname;
	}
	else
	{
		trigname = stmt->trigname;
		constrname = "";
	}

	TRIGGER_CLEAR_TYPE(tgtype);
	if (stmt->before)
		TRIGGER_SETT_BEFORE(tgtype);
	if (stmt->row)
		TRIGGER_SETT_ROW(tgtype);

	for (i = 0; stmt->actions[i]; i++)
	{
		switch (stmt->actions[i])
		{
			case 'i':
				if (TRIGGER_FOR_INSERT(tgtype))
					ereport(ERROR,
							(errcode(ERRCODE_SYNTAX_ERROR),
							 errmsg("multiple INSERT events specified")));
				TRIGGER_SETT_INSERT(tgtype);
				break;
			case 'd':
				if (TRIGGER_FOR_DELETE(tgtype))
					ereport(ERROR,
							(errcode(ERRCODE_SYNTAX_ERROR),
							 errmsg("multiple DELETE events specified")));
				TRIGGER_SETT_DELETE(tgtype);
				break;
			case 'u':
				if (TRIGGER_FOR_UPDATE(tgtype))
					ereport(ERROR,
							(errcode(ERRCODE_SYNTAX_ERROR),
							 errmsg("multiple UPDATE events specified")));
				TRIGGER_SETT_UPDATE(tgtype);
				break;
			default:
				elog(ERROR, "unrecognized trigger event: %d",
					 (int) stmt->actions[i]);
				break;
		}
	}

	/*
	 * 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,
						   F_OIDEQ,
						   ObjectIdGetDatum(RelationGetRelid(rel)));
	tgscan = systable_beginscan(tgrel, TriggerRelidNameIndex, true,
								SnapshotNow, 1, &key);
	while (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
	{
		Form_pg_trigger pg_trigger = (Form_pg_trigger) GETSTRUCT(tuple);

		if (namestrcmp(&(pg_trigger->tgname), trigname) == 0)
			ereport(ERROR,
					(errcode(ERRCODE_DUPLICATE_OBJECT),
			  errmsg("trigger \"%s\" for relation \"%s\" already exists",
					 trigname, stmt->relation->relname)));
		found++;
	}
	systable_endscan(tgscan);

	/*
	 * Find and validate the trigger function.
	 */
	MemSet(fargtypes, 0, FUNC_MAX_ARGS * sizeof(Oid));
	funcoid = LookupFuncName(stmt->funcname, 0, fargtypes, false);
	funcrettype = get_func_rettype(funcoid);
	if (funcrettype != TRIGGEROID)
	{
		/*
		 * We allow OPAQUE just so we can load old dump files.	When we
		 * see a trigger function declared OPAQUE, change it to TRIGGER.
		 */
		if (funcrettype == OPAQUEOID)
		{
			ereport(WARNING,
					(errmsg("changing return type of function %s from \"opaque\" to \"trigger\"",
							NameListToString(stmt->funcname))));
			SetFunctionReturnType(funcoid, TRIGGEROID);
		}
		else
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
					 errmsg("function %s must return type \"trigger\"",
							NameListToString(stmt->funcname))));
	}

	/*
	 * Build the new pg_trigger tuple.
	 */
	MemSet(nulls, ' ', Natts_pg_trigger * sizeof(char));

	values[Anum_pg_trigger_tgrelid - 1] = ObjectIdGetDatum(RelationGetRelid(rel));
	values[Anum_pg_trigger_tgname - 1] = DirectFunctionCall1(namein,
											  CStringGetDatum(trigname));
	values[Anum_pg_trigger_tgfoid - 1] = ObjectIdGetDatum(funcoid);
	values[Anum_pg_trigger_tgtype - 1] = Int16GetDatum(tgtype);
	values[Anum_pg_trigger_tgenabled - 1] = BoolGetDatum(true);
	values[Anum_pg_trigger_tgisconstraint - 1] = BoolGetDatum(stmt->isconstraint);
	values[Anum_pg_trigger_tgconstrname - 1] = DirectFunctionCall1(namein,
											CStringGetDatum(constrname));
	values[Anum_pg_trigger_tgconstrrelid - 1] = ObjectIdGetDatum(constrrelid);
	values[Anum_pg_trigger_tgdeferrable - 1] = BoolGetDatum(stmt->deferrable);
	values[Anum_pg_trigger_tginitdeferred - 1] = BoolGetDatum(stmt->initdeferred);

	if (stmt->args)
	{
		List	   *le;
		char	   *args;
		int16		nargs = length(stmt->args);
		int			len = 0;

		foreach(le, stmt->args)
		{
			char	   *ar = strVal(lfirst(le));

			len += strlen(ar) + 4;
			for (; *ar; ar++)
			{
				if (*ar == '\\')
					len++;
			}
		}
		args = (char *) palloc(len + 1);
		args[0] = '\0';
		foreach(le, stmt->args)
		{
			char	   *s = strVal(lfirst(le));
			char	   *d = args + strlen(args);

			while (*s)
			{
				if (*s == '\\')
					*d++ = '\\';
				*d++ = *s++;
			}
			strcpy(d, "\\000");
		}
		values[Anum_pg_trigger_tgnargs - 1] = Int16GetDatum(nargs);
		values[Anum_pg_trigger_tgargs - 1] = DirectFunctionCall1(byteain,
												  CStringGetDatum(args));
	}
	else
	{
		values[Anum_pg_trigger_tgnargs - 1] = Int16GetDatum(0);
		values[Anum_pg_trigger_tgargs - 1] = DirectFunctionCall1(byteain,
													CStringGetDatum(""));
	}
	MemSet(tgattr, 0, FUNC_MAX_ARGS * sizeof(int16));
	values[Anum_pg_trigger_tgattr - 1] = PointerGetDatum(tgattr);

	tuple = heap_formtuple(tgrel->rd_att, values, nulls);

	/* force tuple to have the desired OID */
	HeapTupleSetOid(tuple, trigoid);

	/*
	 * Insert tuple into pg_trigger.
	 */
	simple_heap_insert(tgrel, tuple);

	CatalogUpdateIndexes(tgrel, tuple);

	myself.classId = RelationGetRelid(tgrel);
	myself.objectId = trigoid;
	myself.objectSubId = 0;

	heap_freetuple(tuple);
	heap_close(tgrel, RowExclusiveLock);

	pfree(DatumGetPointer(values[Anum_pg_trigger_tgname - 1]));
	pfree(DatumGetPointer(values[Anum_pg_trigger_tgargs - 1]));

	/*
	 * 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.
	 */
	pgrel = heap_openr(RelationRelationName, RowExclusiveLock);
	tuple = SearchSysCacheCopy(RELOID,
							   ObjectIdGetDatum(RelationGetRelid(rel)),
							   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for relation %u",
			 RelationGetRelid(rel));

	((Form_pg_class) GETSTRUCT(tuple))->reltriggers = found + 1;

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

	CatalogUpdateIndexes(pgrel, tuple);

	heap_freetuple(tuple);
	heap_close(pgrel, RowExclusiveLock);

	/*
	 * We used to try to update the rel's relcache entry here, but that's
	 * fairly pointless since it will happen as a byproduct of the
	 * upcoming CommandCounterIncrement...
	 */

	/*
	 * Record dependencies for trigger.  Always place a normal dependency
	 * on the function.  If we are doing this in response to an explicit
	 * CREATE TRIGGER command, also make trigger be auto-dropped if its
	 * relation is dropped or if the FK relation is dropped.  (Auto drop
	 * is compatible with our pre-7.3 behavior.)  If the trigger is being
	 * made for a constraint, we can skip the relation links; the
	 * dependency on the constraint will indirectly depend on the
	 * relations.
	 */
	referenced.classId = RelOid_pg_proc;
	referenced.objectId = funcoid;
	referenced.objectSubId = 0;
	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);

	if (!forConstraint)
	{
		referenced.classId = RelOid_pg_class;
		referenced.objectId = RelationGetRelid(rel);
		referenced.objectSubId = 0;
		recordDependencyOn(&myself, &referenced, DEPENDENCY_AUTO);
		if (constrrelid != InvalidOid)
		{
			referenced.classId = RelOid_pg_class;
			referenced.objectId = constrrelid;
			referenced.objectSubId = 0;
			recordDependencyOn(&myself, &referenced, DEPENDENCY_AUTO);
		}
	}

	/* Keep lock on target rel until end of xact */
	heap_close(rel, NoLock);

	return trigoid;
}

/*
 * DropTrigger - drop an individual trigger by name
 */
void
DropTrigger(Oid relid, const char *trigname, DropBehavior behavior)
{
	Relation	tgrel;
	ScanKeyData skey[2];
	SysScanDesc tgscan;
	HeapTuple	tup;
	ObjectAddress object;

	/*
	 * Find the trigger, verify permissions, set up object address
	 */
	tgrel = heap_openr(TriggerRelationName, AccessShareLock);

	ScanKeyEntryInitialize(&skey[0], 0x0,
						   Anum_pg_trigger_tgrelid, F_OIDEQ,
						   ObjectIdGetDatum(relid));

	ScanKeyEntryInitialize(&skey[1], 0x0,
						   Anum_pg_trigger_tgname, F_NAMEEQ,
						   CStringGetDatum(trigname));

	tgscan = systable_beginscan(tgrel, TriggerRelidNameIndex, 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,