From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 4 Jul 2026 15:34:26 +0000 (-0400)
Subject: Disallow renaming a rule to "_RETURN".
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e99fb3262441b47d88632b2857f03083be67f3e3;p=thirdparty%2Fpostgresql.git

Disallow renaming a rule to "_RETURN".

ON SELECT rules must be named "_RETURN", while other kinds of rules
must not be; this ancient restriction is depended on by various client
code.  We successfully enforced this convention in most places, but
ALTER RULE allowed renaming a non-SELECT rule to "_RETURN".  Notably,
that would break dump/restore, since the eventual CREATE RULE command
would reject the name.

While at it, remove DefineQueryRewrite's hack to substitute "_RETURN"
for the convention that was used before 7.3.  We dropped other
server-side code that supported restoring pre-7.3 dumps some time ago
(notably in e58a59975 and nearby commits), but this bit was missed.

Bug: #19543
Reported-by: Adam Pickering <adamkpickering@gmail.com>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/19543-461228e77f3b32fc@postgresql.org
Backpatch-through: 14
---

diff --git a/src/backend/rewrite/rewriteDefine.c b/src/backend/rewrite/rewriteDefine.c
index 6cc9a8d8bfe..601242ea26d 100644
--- a/src/backend/rewrite/rewriteDefine.c
+++ b/src/backend/rewrite/rewriteDefine.c
@@ -390,26 +390,11 @@ DefineQueryRewrite(const char *rulename,
 		 * ... and finally the rule must be named _RETURN.
 		 */
 		if (strcmp(rulename, ViewSelectRuleName) != 0)
-		{
-			/*
-			 * In versions before 7.3, the expected name was _RETviewname. For
-			 * backwards compatibility with old pg_dump output, accept that
-			 * and silently change it to _RETURN.  Since this is just a quick
-			 * backwards-compatibility hack, limit the number of characters
-			 * checked to a few less than NAMEDATALEN; this saves having to
-			 * worry about where a multibyte character might have gotten
-			 * truncated.
-			 */
-			if (strncmp(rulename, "_RET", 4) != 0 ||
-				strncmp(rulename + 4, RelationGetRelationName(event_relation),
-						NAMEDATALEN - 4 - 4) != 0)
-				ereport(ERROR,
-						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
-						 errmsg("view rule for \"%s\" must be named \"%s\"",
-								RelationGetRelationName(event_relation),
-								ViewSelectRuleName)));
-			rulename = pstrdup(ViewSelectRuleName);
-		}
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("view rule for \"%s\" must be named \"%s\"",
+							RelationGetRelationName(event_relation),
+							ViewSelectRuleName)));
 	}
 	else
 	{
@@ -844,6 +829,17 @@ RenameRewriteRule(RangeVar *relation, const char *oldName,
 				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
 				 errmsg("renaming an ON SELECT rule is not allowed")));
 
+	/*
+	 * Conversely, if it's not an ON SELECT rule then it must *not* be named
+	 * _RETURN.
+	 */
+	if (strcmp(newName, ViewSelectRuleName) == 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("non-view rule for \"%s\" must not be named \"%s\"",
+						RelationGetRelationName(targetrel),
+						ViewSelectRuleName)));
+
 	/* OK, do the update */
 	namestrcpy(&(ruleform->rulename), newName);
 
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 13178e2b3df..60eb4c431ce 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -3199,6 +3199,8 @@ ALTER RULE NewInsertRule ON rule_v1 RENAME TO "_RETURN"; -- already exists
 ERROR:  rule "_RETURN" for relation "rule_v1" already exists
 ALTER RULE "_RETURN" ON rule_v1 RENAME TO abc; -- ON SELECT rule cannot be renamed
 ERROR:  renaming an ON SELECT rule is not allowed
+ALTER RULE rtest_t4_ins1 ON rtest_t4 RENAME TO "_RETURN"; -- also disallowed
+ERROR:  non-view rule for "rtest_t4" must not be named "_RETURN"
 DROP VIEW rule_v1;
 DROP TABLE rule_t1;
 --
diff --git a/src/test/regress/sql/rules.sql b/src/test/regress/sql/rules.sql
index 4a5fa505855..999b53f51a5 100644
--- a/src/test/regress/sql/rules.sql
+++ b/src/test/regress/sql/rules.sql
@@ -1087,6 +1087,7 @@ SELECT * FROM rule_v1;
 ALTER RULE InsertRule ON rule_v1 RENAME TO NewInsertRule; -- doesn't exist
 ALTER RULE NewInsertRule ON rule_v1 RENAME TO "_RETURN"; -- already exists
 ALTER RULE "_RETURN" ON rule_v1 RENAME TO abc; -- ON SELECT rule cannot be renamed
+ALTER RULE rtest_t4_ins1 ON rtest_t4 RENAME TO "_RETURN"; -- also disallowed
 
 DROP VIEW rule_v1;
 DROP TABLE rule_t1;