Improve conversion of legacy CREATE CONSTRAINT TRIGGER representation of

foreign keys, one more time.  Insist on matching up all three triggers before
we create a constraint; this will avoid creation of duplicate constraints
in scenarios where a broken FK constraint was repaired by re-adding the
constraint without removing the old partial trigger set.  Basically, this will
work nicely in all cases where the FK was actually functioning correctly in
the database that was dumped.  It will fail to restore an FK in just one case
where we theoretically could restore it: where we find the referenced table's
triggers and not the referencing table's trigger.  However, in such a scenario
it's likely that the user doesn't even realize he still has an FK at all
(since the more-likely-to-fail cases aren't enforced), and we'd probably not
accomplish much except to cause the reload to fail because the data doesn't
meet the FK constraint.  Also make the NOTICE logging still more verbose, by
adding detail about which of the triggers were found.  This seems about all
we can do without solving the problem of getting the user's attention at
session end.

Author: tglsfdc

src/backend/commands/trigger.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.221 2007/11/04 21:25:55 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.222 2007/11/05 19:00:25 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -222,11 +222,11 @@ CreateTrigger(CreateTrigStmt *stmt, Oid constraintOid)
 		(list_length(stmt->args) % 2) == 0 &&
 		RI_FKey_trigger_type(funcoid) != RI_TRIGGER_NONE)
 	{
-		ConvertTriggerToFK(stmt, funcoid);
-
 		/* Keep lock on target rel until end of xact */
 		heap_close(rel, NoLock);
 
+		ConvertTriggerToFK(stmt, funcoid);
+
 		return InvalidOid;
 	}
 
@@ -462,33 +462,44 @@ CreateTrigger(CreateTrigStmt *stmt, Oid constraintOid)
  *
  * The conversion is complex because a pre-7.3 foreign key involved three
  * separate triggers, which were reported separately in dumps.  While the
- * single trigger on the referencing table can be ignored, we need info
- * from both of the triggers on the referenced table to build the constraint
- * declaration.  Our approach is to save info from the first trigger seen
- * in a list in TopMemoryContext.  When we see the second trigger we can
- * create the FK constraint and remove the list entry.  We match triggers
- * together by comparing the trigger arguments (which include constraint
- * name, table and column names, so should be good enough).
+ * single trigger on the referencing table adds no new information, we need
+ * to know the trigger functions of both of the triggers on the referenced
+ * table to build the constraint declaration.  Also, due to lack of proper
+ * dependency checking pre-7.3, it is possible that the source database had
+ * an incomplete set of triggers resulting in an only partially enforced
+ * FK constraint.  (This would happen if one of the tables had been dropped
+ * and re-created, but only if the DB had been affected by a 7.0 pg_dump bug
+ * that caused loss of tgconstrrelid information.)  We choose to translate to
+ * an FK constraint only when we've seen all three triggers of a set.  This is
+ * implemented by storing unmatched items in a list in TopMemoryContext.
+ * We match triggers together by comparing the trigger arguments (which
+ * include constraint name, table and column names, so should be good enough).
  */
 typedef struct {
 	List	   *args;			/* list of (T_String) Values or NIL */
-	Oid			funcoid;		/* OID of trigger function */
-	bool		isupd;			/* is it the UPDATE trigger? */
+	Oid			funcoids[3];	/* OIDs of trigger functions */
+	/* The three function OIDs are stored in the order update, delete, child */
 } OldTriggerInfo;
 
 static void
 ConvertTriggerToFK(CreateTrigStmt *stmt, Oid funcoid)
 {
 	static List *info_list = NIL;
 
+	static const char * const funcdescr[3] = {
+		gettext_noop("Found referenced table's UPDATE trigger."),
+		gettext_noop("Found referenced table's DELETE trigger."),
+		gettext_noop("Found referencing table's trigger.")
+	};
+
 	char	   *constr_name;
 	char	   *fk_table_name;
 	char	   *pk_table_name;
 	char		fk_matchtype = FKCONSTR_MATCH_UNSPECIFIED;
 	List	   *fk_attrs = NIL;
 	List	   *pk_attrs = NIL;
 	StringInfoData buf;
-	bool		isupd;
+	int			funcnum;
 	OldTriggerInfo *info = NULL;
 	ListCell   *l;
 	int			i;
@@ -548,73 +559,99 @@ ConvertTriggerToFK(CreateTrigStmt *stmt, Oid funcoid)
 	/* Identify class of trigger --- update, delete, or referencing-table */
 	switch (funcoid)
 	{
-		case F_RI_FKEY_CASCADE_DEL:
-		case F_RI_FKEY_RESTRICT_DEL:
-		case F_RI_FKEY_SETNULL_DEL:
-		case F_RI_FKEY_SETDEFAULT_DEL:
-		case F_RI_FKEY_NOACTION_DEL:
-			isupd = false;
-			break;
-
 		case F_RI_FKEY_CASCADE_UPD:
 		case F_RI_FKEY_RESTRICT_UPD:
 		case F_RI_FKEY_SETNULL_UPD:
 		case F_RI_FKEY_SETDEFAULT_UPD:
 		case F_RI_FKEY_NOACTION_UPD:
-			isupd = true;
+			funcnum = 0;
+			break;
+
+		case F_RI_FKEY_CASCADE_DEL:
+		case F_RI_FKEY_RESTRICT_DEL:
+		case F_RI_FKEY_SETNULL_DEL:
+		case F_RI_FKEY_SETDEFAULT_DEL:
+		case F_RI_FKEY_NOACTION_DEL:
+			funcnum = 1;
 			break;
 
 		default:
-			/* Ignore triggers on referencing table */
-			ereport(NOTICE,
-					(errmsg("ignoring incomplete trigger group for constraint \"%s\" %s",
-							constr_name, buf.data)));
-			return;
+			funcnum = 2;
+			break;
 	}
 
 	/* See if we have a match to this trigger */
 	foreach(l, info_list)
 	{
 		info = (OldTriggerInfo *) lfirst(l);
-		if (info->isupd != isupd && equal(info->args, stmt->args))
+		if (info->funcoids[funcnum] == InvalidOid &&
+			equal(info->args, stmt->args))
+		{
+			info->funcoids[funcnum] = funcoid;
 			break;
+		}
 	}
 
 	if (l == NULL)
 	{
-		/* First trigger of pair, so save away what we need */
+		/* First trigger of set, so create a new list entry */
 		MemoryContext oldContext;
 
 		ereport(NOTICE,
 				(errmsg("ignoring incomplete trigger group for constraint \"%s\" %s",
-						constr_name, buf.data)));
+						constr_name, buf.data),
+				 errdetail(funcdescr[funcnum])));
 		oldContext = MemoryContextSwitchTo(TopMemoryContext);
-		info = (OldTriggerInfo *) palloc(sizeof(OldTriggerInfo));
+		info = (OldTriggerInfo *) palloc0(sizeof(OldTriggerInfo));
 		info->args = copyObject(stmt->args);
-		info->funcoid = funcoid;
-		info->isupd = isupd;
+		info->funcoids[funcnum] = funcoid;
 		info_list = lappend(info_list, info);
 		MemoryContextSwitchTo(oldContext);
 	}
+	else if (info->funcoids[0] == InvalidOid ||
+			 info->funcoids[1] == InvalidOid ||
+			 info->funcoids[2] == InvalidOid)
+	{
+		/* Second trigger of set */
+		ereport(NOTICE,
+				(errmsg("ignoring incomplete trigger group for constraint \"%s\" %s",
+						constr_name, buf.data),
+				 errdetail(funcdescr[funcnum])));
+	}
 	else
 	{
-		/* OK, we have a pair, so make the FK constraint ALTER TABLE cmd */
+		/* OK, we have a set, so make the FK constraint ALTER TABLE cmd */
 		AlterTableStmt *atstmt = makeNode(AlterTableStmt);
 		AlterTableCmd *atcmd = makeNode(AlterTableCmd);
 		FkConstraint *fkcon = makeNode(FkConstraint);
-		Oid		updfunc,
-				delfunc;
 
 		ereport(NOTICE,
 				(errmsg("converting trigger group into constraint \"%s\" %s",
-						constr_name, buf.data)));
-
-		if (stmt->constrrel)
-			atstmt->relation = stmt->constrrel;
+						constr_name, buf.data),
+				 errdetail(funcdescr[funcnum])));
+		if (funcnum == 2)
+		{
+			/* This trigger is on the FK table */
+			atstmt->relation = stmt->relation;
+			if (stmt->constrrel)
+				fkcon->pktable = stmt->constrrel;
+			else
+			{
+				/* Work around ancient pg_dump bug that omitted constrrel */
+				fkcon->pktable = makeRangeVar(NULL, pk_table_name);
+			}
+		}
 		else
 		{
-			/* Work around ancient pg_dump bug that omitted constrrel */
-			atstmt->relation = makeRangeVar(NULL, fk_table_name);
+			/* This trigger is on the PK table */
+			fkcon->pktable = stmt->relation;
+			if (stmt->constrrel)
+				atstmt->relation = stmt->constrrel;
+			else
+			{
+				/* Work around ancient pg_dump bug that omitted constrrel */
+				atstmt->relation = makeRangeVar(NULL, fk_table_name);
+			}
 		}
 		atstmt->cmds = list_make1(atcmd);
 		atstmt->relkind = OBJECT_TABLE;
@@ -624,22 +661,10 @@ ConvertTriggerToFK(CreateTrigStmt *stmt, Oid funcoid)
 			fkcon->constr_name = NULL;
 		else
 			fkcon->constr_name = constr_name;
-		fkcon->pktable = stmt->relation;
 		fkcon->fk_attrs = fk_attrs;
 		fkcon->pk_attrs = pk_attrs;
 		fkcon->fk_matchtype = fk_matchtype;
-
-		if (isupd)
-		{
-			updfunc = funcoid;
-			delfunc = info->funcoid;
-		}
-		else
-		{
-			updfunc = info->funcoid;
-			delfunc = funcoid;
-		}
-		switch (updfunc)
+		switch (info->funcoids[0])
 		{
 			case F_RI_FKEY_NOACTION_UPD:
 				fkcon->fk_upd_action = FKCONSTR_ACTION_NOACTION;
@@ -660,7 +685,7 @@ ConvertTriggerToFK(CreateTrigStmt *stmt, Oid funcoid)
 				/* can't get here because of earlier checks */
 				elog(ERROR, "confused about RI update function");
 		}
-		switch (delfunc)
+		switch (info->funcoids[1])
 		{
 			case F_RI_FKEY_NOACTION_DEL:
 				fkcon->fk_del_action = FKCONSTR_ACTION_NOACTION;