Fix partitioned index attachment

When an existing index in a partition is attached to a new index on
its parent, we forgot to set the "relispartition" flag correctly, which
meant that it was not possible to find the index in various operations,
such as adding a foreign key constraint that references that partitioned
table.  One of four places that was assigning the parent index was
forgetting to do that, so fix by shifting responsibility of updating the
flag to the routine that changes the parent.

Author: Amit Langote, Álvaro Herrera
Reported-by: Hubert "depesz" Lubaczewski
Discussion: https://postgr.es/m/CA+HiwqHMsRtRYRWYTWavKJ8x14AFsv7bmAV46mYwnfD3vy8goQ@mail.gmail.com

src/backend/commands/indexcmds.c

@@ -89,6 +89,7 @@ static void RangeVarCallbackForReindexIndex(const RangeVar *relation,
 								Oid relId, Oid oldRelId, void *arg);
 static bool ReindexRelationConcurrently(Oid relationOid, int options);
 static void ReindexPartitionedIndex(Relation parentIdx);
+static void update_relispartition(Oid relationId, bool newval);
 
 /*
  * CheckIndexCompatible
@@ -3388,6 +3389,9 @@ IndexSetParentIndex(Relation partitionIdx, Oid parentOid)
 	if (OidIsValid(parentOid))
 		SetRelationHasSubclass(parentOid, true);
 
+	/* set relispartition correctly on the partition */
+	update_relispartition(partRelid, OidIsValid(parentOid));
+
 	if (fix_dependencies)
 	{
 		/*
@@ -3424,3 +3428,23 @@ IndexSetParentIndex(Relation partitionIdx, Oid parentOid)
 		CommandCounterIncrement();
 	}
 }
+
+/*
+ * Subroutine of IndexSetParentIndex to update the relispartition flag of the
+ * given index to the given value.
+ */
+static void
+update_relispartition(Oid relationId, bool newval)
+{
+	HeapTuple	tup;
+	Relation	classRel;
+
+	classRel = table_open(RelationRelationId, RowExclusiveLock);
+	tup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relationId));
+	Assert(((Form_pg_class) GETSTRUCT(tup))->relispartition != newval);
+	((Form_pg_class) GETSTRUCT(tup))->relispartition = newval;
+	CatalogTupleUpdate(classRel, &tup->t_self, tup);
+	heap_freetuple(tup);
+
+	table_close(classRel, RowExclusiveLock);
+}

src/backend/commands/tablecmds.c

@@ -525,8 +525,6 @@ static ObjectAddress ATExecAttachPartitionIdx(List **wqueue, Relation rel,
 static void validatePartitionedIndex(Relation partedIdx, Relation partedTbl);
 static void refuseDupeIndexAttach(Relation parentIdx, Relation partIdx,
 					  Relation partitionTbl);
-static void update_relispartition(Relation classRel, Oid relationId,
-					  bool newval);
 static List *GetParentedForeignKeyRefs(Relation partition);
 static void ATDetachCheckNoForeignKeyRefs(Relation partition);
 
@@ -15714,7 +15712,6 @@ AttachPartitionEnsureIndexes(Relation rel, Relation attachrel)
 				if (OidIsValid(constraintOid))
 					ConstraintSetParentConstraint(cldConstrOid, constraintOid,
 												  RelationGetRelid(attachrel));
-				update_relispartition(NULL, cldIdxId, true);
 				found = true;
 
 				CommandCounterIncrement();
@@ -15970,7 +15967,6 @@ ATExecDetachPartition(Relation rel, RangeVar *name)
 
 		idx = index_open(idxid, AccessExclusiveLock);
 		IndexSetParentIndex(idx, InvalidOid);
-		update_relispartition(classRel, idxid, false);
 
 		/* If there's a constraint associated with the index, detach it too */
 		constrOid = get_relation_idx_constraint_oid(RelationGetRelid(partRel),
@@ -16268,7 +16264,6 @@ ATExecAttachPartitionIdx(List **wqueue, Relation parentIdx, RangeVar *name)
 		if (OidIsValid(constraintOid))
 			ConstraintSetParentConstraint(cldConstrId, constraintOid,
 										  RelationGetRelid(partTbl));
-		update_relispartition(NULL, partIdxId, true);
 
 		pfree(attmap);
 
@@ -16401,38 +16396,6 @@ validatePartitionedIndex(Relation partedIdx, Relation partedTbl)
 	}
 }
 
-/*
- * Update the relispartition flag of the given relation to the given value.
- *
- * classRel is the pg_class relation, already open and suitably locked.
- * It can be passed as NULL, in which case it's opened and closed locally.
- */
-static void
-update_relispartition(Relation classRel, Oid relationId, bool newval)
-{
-	HeapTuple	tup;
-	HeapTuple	newtup;
-	Form_pg_class classForm;
-	bool		opened = false;
-
-	if (classRel == NULL)
-	{
-		classRel = table_open(RelationRelationId, RowExclusiveLock);
-		opened = true;
-	}
-
-	tup = SearchSysCache1(RELOID, ObjectIdGetDatum(relationId));
-	newtup = heap_copytuple(tup);
-	classForm = (Form_pg_class) GETSTRUCT(newtup);
-	classForm->relispartition = newval;
-	CatalogTupleUpdate(classRel, &tup->t_self, newtup);
-	heap_freetuple(newtup);
-	ReleaseSysCache(tup);
-
-	if (opened)
-		table_close(classRel, RowExclusiveLock);
-}
-
 /*
  * Return an OID list of constraints that reference the given relation
  * that are marked as having a parent constraints.

src/test/regress/expected/foreign_key.out

@@ -2367,3 +2367,15 @@ SELECT tableoid::regclass, * FROM fk;
 (2 rows)
 
 DROP TABLE fk;
+-- test for reported bug: relispartition not set
+-- https://postgr.es/m/CA+HiwqHMsRtRYRWYTWavKJ8x14AFsv7bmAV46mYwnfD3vy8goQ@mail.gmail.com
+CREATE SCHEMA fkpart7
+  CREATE TABLE pkpart (a int) PARTITION BY LIST (a)
+  CREATE TABLE pkpart1 PARTITION OF pkpart FOR VALUES IN (1);
+ALTER TABLE fkpart7.pkpart1 ADD PRIMARY KEY (a);
+ALTER TABLE fkpart7.pkpart ADD PRIMARY KEY (a);
+CREATE TABLE fkpart7.fk (a int REFERENCES fkpart7.pkpart);
+DROP SCHEMA fkpart7 CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to table fkpart7.pkpart
+drop cascades to table fkpart7.fk

src/test/regress/sql/foreign_key.sql

@@ -1657,3 +1657,13 @@ DELETE FROM pk WHERE a = 20;
 UPDATE pk SET a = 90 WHERE a = 30;
 SELECT tableoid::regclass, * FROM fk;
 DROP TABLE fk;
+
+-- test for reported bug: relispartition not set
+-- https://postgr.es/m/CA+HiwqHMsRtRYRWYTWavKJ8x14AFsv7bmAV46mYwnfD3vy8goQ@mail.gmail.com
+CREATE SCHEMA fkpart7
+  CREATE TABLE pkpart (a int) PARTITION BY LIST (a)
+  CREATE TABLE pkpart1 PARTITION OF pkpart FOR VALUES IN (1);
+ALTER TABLE fkpart7.pkpart1 ADD PRIMARY KEY (a);
+ALTER TABLE fkpart7.pkpart ADD PRIMARY KEY (a);
+CREATE TABLE fkpart7.fk (a int REFERENCES fkpart7.pkpart);
+DROP SCHEMA fkpart7 CASCADE;