Fix self-referencing foreign keys with partitioned tables

There are a number of bugs in this area.  Two of them are fixed here,
namely:
1. get_relation_idx_constraint_oid does not restrict the type of
   constraint that's returned, so with sufficient bad luck it can
   return the OID of a foreign key constraint.  This has the effect that
   a primary key in a partition can end up as a child of a foreign key,
   which makes no sense (it needs to be the child of the equivalent
   primary key.)
   Change the API contract so that only index-backed constraints are
   returned, mimicking get_constraint_index().

2. Both CloneFkReferenced and CloneFkReferencing clone a
   self-referencing foreign key, so the partition ends up with
   a duplicate foreign key.  Change the former function to ignore such
   constraints.

Add some tests to verify that things are better now.  (However, these
new tests show some additional misbehavior that will be fixed later --
namely that there's a constraint marked NOT VALID.)

Backpatch to 12, where these constraints are possible at all.

Author: Jehan-Guillaume de Rorthais <jgdr@dalibo.com>
Discussion: https://postgr.es/m/20220603154232.1715b14c@karst

src/backend/catalog/pg_constraint.c

@@ -973,8 +973,12 @@ get_relation_constraint_attnos(Oid relid, const char *conname,
 }
 
 /*
- * Return the OID of the constraint associated with the given index in the
+ * Return the OID of the constraint enforced by the given index in the
  * given relation; or InvalidOid if no such index is catalogued.
+ *
+ * Much like get_constraint_index, this function is concerned only with the
+ * one constraint that "owns" the given index.  Therefore, constraints of
+ * types other than unique, primary-key, and exclusion are ignored.
  */
 Oid
 get_relation_idx_constraint_oid(Oid relationId, Oid indexId)
@@ -999,6 +1003,13 @@ get_relation_idx_constraint_oid(Oid relationId, Oid indexId)
 		Form_pg_constraint constrForm;
 
 		constrForm = (Form_pg_constraint) GETSTRUCT(tuple);
+
+		/* See above */
+		if (constrForm->contype != CONSTRAINT_PRIMARY &&
+			constrForm->contype != CONSTRAINT_UNIQUE &&
+			constrForm->contype != CONSTRAINT_EXCLUSION)
+			continue;
+
 		if (constrForm->conindid == indexId)
 		{
 			constraintId = constrForm->oid;

src/backend/commands/tablecmds.c

@@ -9749,6 +9749,8 @@ CloneForeignKeyConstraints(List **wqueue, Relation parentRel,
  * clone those constraints to the given partition.  This is to be called
  * when the partition is being created or attached.
  *
+ * This ignores self-referencing FKs; those are handled by CloneFkReferencing.
+ *
  * This recurses to partitions, if the relation being attached is partitioned.
  * Recursion is done by calling addFkRecurseReferenced.
  */
@@ -9824,6 +9826,17 @@ CloneFkReferenced(Relation parentRel, Relation partitionRel)
 			continue;
 		}
 
+		/*
+		 * Don't clone self-referencing foreign keys, which can be in the
+		 * partitioned table or in the partition-to-be.
+		 */
+		if (constrForm->conrelid == RelationGetRelid(parentRel) ||
+			constrForm->conrelid == RelationGetRelid(partitionRel))
+		{
+			ReleaseSysCache(tuple);
+			continue;
+		}
+
 		/*
 		 * Because we're only expanding the key space at the referenced side,
 		 * we don't need to prevent any operation in the referencing table, so

src/test/regress/expected/foreign_key.out

@@ -1921,6 +1921,87 @@ drop table other_partitioned_fk;
 reset role;
 revoke all on fk_notpartitioned_pk from regress_other_partitioned_fk_owner;
 drop role regress_other_partitioned_fk_owner;
+--
+-- Test self-referencing foreign key with partition.
+-- This should create only one fk constraint per partition
+--
+CREATE TABLE parted_self_fk (
+    id bigint NOT NULL PRIMARY KEY,
+    id_abc bigint,
+    FOREIGN KEY (id_abc) REFERENCES parted_self_fk(id)
+)
+PARTITION BY RANGE (id);
+CREATE TABLE part1_self_fk (
+    id bigint NOT NULL PRIMARY KEY,
+    id_abc bigint
+);
+ALTER TABLE parted_self_fk ATTACH PARTITION part1_self_fk FOR VALUES FROM (0) TO (10);
+CREATE TABLE part2_self_fk PARTITION OF parted_self_fk FOR VALUES FROM (10) TO (20);
+CREATE TABLE part3_self_fk (	-- a partitioned partition
+	id bigint NOT NULL PRIMARY KEY,
+	id_abc bigint
+) PARTITION BY RANGE (id);
+CREATE TABLE part32_self_fk PARTITION OF part3_self_fk FOR VALUES FROM (20) TO (30);
+ALTER TABLE parted_self_fk ATTACH PARTITION part3_self_fk FOR VALUES FROM (20) TO (40);
+CREATE TABLE part33_self_fk (
+	id bigint NOT NULL PRIMARY KEY,
+	id_abc bigint
+);
+ALTER TABLE part3_self_fk ATTACH PARTITION part33_self_fk FOR VALUES FROM (30) TO (40);
+SELECT cr.relname, co.conname, co.contype, co.convalidated,
+       p.conname AS conparent, p.convalidated, cf.relname AS foreignrel
+FROM pg_constraint co
+JOIN pg_class cr ON cr.oid = co.conrelid
+LEFT JOIN pg_class cf ON cf.oid = co.confrelid
+LEFT JOIN pg_constraint p ON p.oid = co.conparentid
+WHERE cr.oid IN (SELECT relid FROM pg_partition_tree('parted_self_fk'))
+ORDER BY co.contype, cr.relname, co.conname, p.conname;
+    relname     |          conname           | contype | convalidated |         conparent          | convalidated |   foreignrel   
+----------------+----------------------------+---------+--------------+----------------------------+--------------+----------------
+ part1_self_fk  | parted_self_fk_id_abc_fkey | f       | t            | parted_self_fk_id_abc_fkey | t            | parted_self_fk
+ part2_self_fk  | parted_self_fk_id_abc_fkey | f       | t            | parted_self_fk_id_abc_fkey | t            | parted_self_fk
+ part32_self_fk | parted_self_fk_id_abc_fkey | f       | f            | parted_self_fk_id_abc_fkey | t            | parted_self_fk
+ part33_self_fk | parted_self_fk_id_abc_fkey | f       | t            | parted_self_fk_id_abc_fkey | t            | parted_self_fk
+ part3_self_fk  | parted_self_fk_id_abc_fkey | f       | t            | parted_self_fk_id_abc_fkey | t            | parted_self_fk
+ parted_self_fk | parted_self_fk_id_abc_fkey | f       | t            |                            |              | parted_self_fk
+ part1_self_fk  | part1_self_fk_pkey         | p       | t            | parted_self_fk_pkey        | t            | 
+ part2_self_fk  | part2_self_fk_pkey         | p       | t            | parted_self_fk_pkey        | t            | 
+ part32_self_fk | part32_self_fk_pkey        | p       | t            | part3_self_fk_pkey         | t            | 
+ part33_self_fk | part33_self_fk_pkey        | p       | t            | part3_self_fk_pkey         | t            | 
+ part3_self_fk  | part3_self_fk_pkey         | p       | t            | parted_self_fk_pkey        | t            | 
+ parted_self_fk | parted_self_fk_pkey        | p       | t            |                            |              | 
+(12 rows)
+
+-- detach and re-attach multiple times just to ensure everything is kosher
+ALTER TABLE parted_self_fk DETACH PARTITION part2_self_fk;
+ALTER TABLE parted_self_fk ATTACH PARTITION part2_self_fk FOR VALUES FROM (10) TO (20);
+ALTER TABLE parted_self_fk DETACH PARTITION part2_self_fk;
+ALTER TABLE parted_self_fk ATTACH PARTITION part2_self_fk FOR VALUES FROM (10) TO (20);
+SELECT cr.relname, co.conname, co.contype, co.convalidated,
+       p.conname AS conparent, p.convalidated, cf.relname AS foreignrel
+FROM pg_constraint co
+JOIN pg_class cr ON cr.oid = co.conrelid
+LEFT JOIN pg_class cf ON cf.oid = co.confrelid
+LEFT JOIN pg_constraint p ON p.oid = co.conparentid
+WHERE cr.oid IN (SELECT relid FROM pg_partition_tree('parted_self_fk'))
+ORDER BY co.contype, cr.relname, co.conname, p.conname;
+    relname     |          conname           | contype | convalidated |         conparent          | convalidated |   foreignrel   
+----------------+----------------------------+---------+--------------+----------------------------+--------------+----------------
+ part1_self_fk  | parted_self_fk_id_abc_fkey | f       | t            | parted_self_fk_id_abc_fkey | t            | parted_self_fk
+ part2_self_fk  | parted_self_fk_id_abc_fkey | f       | t            | parted_self_fk_id_abc_fkey | t            | parted_self_fk
+ part32_self_fk | parted_self_fk_id_abc_fkey | f       | f            | parted_self_fk_id_abc_fkey | t            | parted_self_fk
+ part33_self_fk | parted_self_fk_id_abc_fkey | f       | t            | parted_self_fk_id_abc_fkey | t            | parted_self_fk
+ part3_self_fk  | parted_self_fk_id_abc_fkey | f       | t            | parted_self_fk_id_abc_fkey | t            | parted_self_fk
+ parted_self_fk | parted_self_fk_id_abc_fkey | f       | t            |                            |              | parted_self_fk
+ part1_self_fk  | part1_self_fk_pkey         | p       | t            | parted_self_fk_pkey        | t            | 
+ part2_self_fk  | part2_self_fk_pkey         | p       | t            | parted_self_fk_pkey        | t            | 
+ part32_self_fk | part32_self_fk_pkey        | p       | t            | part3_self_fk_pkey         | t            | 
+ part33_self_fk | part33_self_fk_pkey        | p       | t            | part3_self_fk_pkey         | t            | 
+ part3_self_fk  | part3_self_fk_pkey         | p       | t            | parted_self_fk_pkey        | t            | 
+ parted_self_fk | parted_self_fk_pkey        | p       | t            |                            |              | 
+(12 rows)
+
+-- Leave this table around, for pg_upgrade/pg_dump tests
 -- Test creating a constraint at the parent that already exists in partitions.
 -- There should be no duplicated constraints, and attempts to drop the
 -- constraint in partitions should raise appropriate errors.

src/test/regress/sql/foreign_key.sql

@@ -1390,6 +1390,61 @@ reset role;
 revoke all on fk_notpartitioned_pk from regress_other_partitioned_fk_owner;
 drop role regress_other_partitioned_fk_owner;
 
+--
+-- Test self-referencing foreign key with partition.
+-- This should create only one fk constraint per partition
+--
+CREATE TABLE parted_self_fk (
+    id bigint NOT NULL PRIMARY KEY,
+    id_abc bigint,
+    FOREIGN KEY (id_abc) REFERENCES parted_self_fk(id)
+)
+PARTITION BY RANGE (id);
+CREATE TABLE part1_self_fk (
+    id bigint NOT NULL PRIMARY KEY,
+    id_abc bigint
+);
+ALTER TABLE parted_self_fk ATTACH PARTITION part1_self_fk FOR VALUES FROM (0) TO (10);
+CREATE TABLE part2_self_fk PARTITION OF parted_self_fk FOR VALUES FROM (10) TO (20);
+CREATE TABLE part3_self_fk (	-- a partitioned partition
+	id bigint NOT NULL PRIMARY KEY,
+	id_abc bigint
+) PARTITION BY RANGE (id);
+CREATE TABLE part32_self_fk PARTITION OF part3_self_fk FOR VALUES FROM (20) TO (30);
+ALTER TABLE parted_self_fk ATTACH PARTITION part3_self_fk FOR VALUES FROM (20) TO (40);
+CREATE TABLE part33_self_fk (
+	id bigint NOT NULL PRIMARY KEY,
+	id_abc bigint
+);
+ALTER TABLE part3_self_fk ATTACH PARTITION part33_self_fk FOR VALUES FROM (30) TO (40);
+
+SELECT cr.relname, co.conname, co.contype, co.convalidated,
+       p.conname AS conparent, p.convalidated, cf.relname AS foreignrel
+FROM pg_constraint co
+JOIN pg_class cr ON cr.oid = co.conrelid
+LEFT JOIN pg_class cf ON cf.oid = co.confrelid
+LEFT JOIN pg_constraint p ON p.oid = co.conparentid
+WHERE cr.oid IN (SELECT relid FROM pg_partition_tree('parted_self_fk'))
+ORDER BY co.contype, cr.relname, co.conname, p.conname;
+
+-- detach and re-attach multiple times just to ensure everything is kosher
+ALTER TABLE parted_self_fk DETACH PARTITION part2_self_fk;
+ALTER TABLE parted_self_fk ATTACH PARTITION part2_self_fk FOR VALUES FROM (10) TO (20);
+ALTER TABLE parted_self_fk DETACH PARTITION part2_self_fk;
+ALTER TABLE parted_self_fk ATTACH PARTITION part2_self_fk FOR VALUES FROM (10) TO (20);
+
+SELECT cr.relname, co.conname, co.contype, co.convalidated,
+       p.conname AS conparent, p.convalidated, cf.relname AS foreignrel
+FROM pg_constraint co
+JOIN pg_class cr ON cr.oid = co.conrelid
+LEFT JOIN pg_class cf ON cf.oid = co.confrelid
+LEFT JOIN pg_constraint p ON p.oid = co.conparentid
+WHERE cr.oid IN (SELECT relid FROM pg_partition_tree('parted_self_fk'))
+ORDER BY co.contype, cr.relname, co.conname, p.conname;
+
+-- Leave this table around, for pg_upgrade/pg_dump tests
+
+
 -- Test creating a constraint at the parent that already exists in partitions.
 -- There should be no duplicated constraints, and attempts to drop the
 -- constraint in partitions should raise appropriate errors.