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commit    797e313dc9aed83e28e9f1d08a281ea48c560cd2
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Mon Oct 17 16:14:39 2022 +0000
First released in: 16.0, 10.23, 11.18, 12.13, 13.9, 14.6, 15.1

    Reject non-ON-SELECT rules that are named "_RETURN".
    
    DefineQueryRewrite() has long required that ON SELECT rules be named
    "_RETURN".  But we overlooked the converse case: we should forbid
    non-ON-SELECT rules that are named "_RETURN".  In particular this
    prevents using CREATE OR REPLACE RULE to overwrite a view's _RETURN
    rule with some other kind of rule, thereby breaking the view.
    
    Per bug #17646 from Kui Liu.  Back-patch to all supported branches.
    
    Discussion: https://postgr.es/m/17646-70c93cfa40365776@postgresql.org


 src/backend/rewrite/rewriteDefine.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/backend/rewrite/rewriteDefine.c b/src/backend/rewrite/rewriteDefine.c
index 213eabfbb9f..09165b269b3 100644
--- a/src/backend/rewrite/rewriteDefine.c
+++ b/src/backend/rewrite/rewriteDefine.c
@@ -530,6 +530,18 @@ DefineQueryRewrite(const char *rulename,
 								RelationGetDescr(event_relation),
 								false, false);
 		}
+
+		/*
+		 * And finally, if it's not an ON SELECT rule then it must *not* be
+		 * named _RETURN.  This prevents accidentally or maliciously replacing
+		 * a view's ON SELECT rule with some other kind of rule.
+		 */
+		if (strcmp(rulename, ViewSelectRuleName) == 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+					 errmsg("non-view rule for \"%s\" must not be named \"%s\"",
+							RelationGetRelationName(event_relation),
+							ViewSelectRuleName)));
 	}
 
 	/*


[parent: eec34661182d]