diff --git a/src/backend/optimizer/plan/analyzejoins.c b/src/backend/optimizer/plan/analyzejoins.c
index 66474b18c60..060118da4ec 100644
--- a/src/backend/optimizer/plan/analyzejoins.c
+++ b/src/backend/optimizer/plan/analyzejoins.c
@@ -2018,7 +2018,7 @@ remove_self_joins_recurse(PlannerInfo *root, List *joinlist)
 	int			j;
 	int			numRels;
 
-	/* Collect indexes of base relations of the join tree */
+	/* Collect indexes of possibly-mergeable relations from the joinlist */
 	foreach(jl, joinlist)
 	{
 		Node	   *jlnode = (Node *) lfirst(jl);
@@ -2029,15 +2029,31 @@ remove_self_joins_recurse(PlannerInfo *root, List *joinlist)
 			RangeTblEntry *rte = root->simple_rte_array[varno];
 
 			/*
-			 * We only consider ordinary relations as candidates to be
-			 * removed, and these relations should not have TABLESAMPLE
-			 * clauses specified.  Removing a relation with TABLESAMPLE clause
-			 * could potentially change the semantics of the query. Because of
-			 * UPDATE/DELETE EPQ mechanism, currently Query->resultRelation or
-			 * Query->mergeTargetRelation associated rel cannot be eliminated.
+			 * To be considered for self-join removal, the RTE must:
+			 *
+			 * 1. Be an ordinary relation.  (Someday we might support SJE on
+			 * partitioned tables, but not yet.)
+			 *
+			 * 2. Not have inh set, ie it has no inheritance children (or the
+			 * user wrote ONLY to ignore them).  Under traditional inheritance
+			 * a unique index on a parent table does not establish uniqueness
+			 * across its children.  This rule also keeps us from trying to
+			 * merge an inheritance scan with an ONLY scan, which would be
+			 * wrong.  (preprocess_relation_rtes already cleared the inh flag
+			 * for tables known not to have inheritance children.)
+			 *
+			 * 3. Not have a TABLESAMPLE clause.  Removing a relation with a
+			 * TABLESAMPLE clause would change the semantics of the query,
+			 * even if we merged it with another RTE with an identical
+			 * TABLESAMPLE clause.  (Two such RTEs should represent
+			 * independent samplings of the base table.)
+			 *
+			 * 4. Not be the query's result relation or MERGE target.  Merging
+			 * would cause misbehavior during EPQ.
 			 */
 			if (rte->rtekind == RTE_RELATION &&
 				rte->relkind == RELKIND_RELATION &&
+				!rte->inh &&
 				rte->tablesample == NULL &&
 				varno != root->parse->resultRelation &&
 				varno != root->parse->mergeTargetRelation)