Add isolation tests for snapshot behavior in ri_triggers.c

They are to check the behavior of RI_FKey_check() and
ri_Check_Pk_Match().  A test case whereby RI_FKey_check() queries a
partitioned PK table under REPEATABLE READ isolation produces wrong
output due to a bug of the partition-descriptor logic and that is noted
as such in the comment in the test.  A subsequent commit will fix the
bug and replace the buggy output by the correct one.

Author: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/1627848.1636676261@sss.pgh.pa.us

src/test/isolation/expected/fk-snapshot.out

@@ -0,0 +1,124 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1brr s2brc s2ip2 s1sp s2c s1sp s1ifp2 s1c s1sfp
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s2brc: BEGIN ISOLATION LEVEL READ COMMITTED;
+step s2ip2: INSERT INTO pk_noparted VALUES (2);
+step s1sp: SELECT * FROM pk_noparted;
+a
+-
+1
+(1 row)
+
+step s2c: COMMIT;
+step s1sp: SELECT * FROM pk_noparted;
+a
+-
+1
+(1 row)
+
+step s1ifp2: INSERT INTO fk_parted_pk VALUES (2);
+ERROR:  insert or update on table "fk_parted_pk_2" violates foreign key constraint "fk_parted_pk_a_fkey"
+step s1c: COMMIT;
+step s1sfp: SELECT * FROM fk_parted_pk;
+a
+-
+1
+(1 row)
+
+
+starting permutation: s2ip2 s2brr s1brc s1ifp2 s2sfp s1c s2sfp s2ifn2 s2c s2sfn
+step s2ip2: INSERT INTO pk_noparted VALUES (2);
+step s2brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1brc: BEGIN ISOLATION LEVEL READ COMMITTED;
+step s1ifp2: INSERT INTO fk_parted_pk VALUES (2);
+step s2sfp: SELECT * FROM fk_parted_pk;
+a
+-
+1
+(1 row)
+
+step s1c: COMMIT;
+step s2sfp: SELECT * FROM fk_parted_pk;
+a
+-
+1
+(1 row)
+
+step s2ifn2: INSERT INTO fk_noparted VALUES (2);
+step s2c: COMMIT;
+step s2sfn: SELECT * FROM fk_noparted;
+a
+-
+1
+2
+(2 rows)
+
+
+starting permutation: s1brc s2brc s2ip2 s1sp s2c s1sp s1ifp2 s2brc s2sfp s1c s1sfp s2ifn2 s2c s2sfn
+step s1brc: BEGIN ISOLATION LEVEL READ COMMITTED;
+step s2brc: BEGIN ISOLATION LEVEL READ COMMITTED;
+step s2ip2: INSERT INTO pk_noparted VALUES (2);
+step s1sp: SELECT * FROM pk_noparted;
+a
+-
+1
+(1 row)
+
+step s2c: COMMIT;
+step s1sp: SELECT * FROM pk_noparted;
+a
+-
+1
+2
+(2 rows)
+
+step s1ifp2: INSERT INTO fk_parted_pk VALUES (2);
+step s2brc: BEGIN ISOLATION LEVEL READ COMMITTED;
+step s2sfp: SELECT * FROM fk_parted_pk;
+a
+-
+1
+(1 row)
+
+step s1c: COMMIT;
+step s1sfp: SELECT * FROM fk_parted_pk;
+a
+-
+1
+2
+(2 rows)
+
+step s2ifn2: INSERT INTO fk_noparted VALUES (2);
+step s2c: COMMIT;
+step s2sfn: SELECT * FROM fk_noparted;
+a
+-
+1
+2
+(2 rows)
+
+
+starting permutation: s1brr s1dfp s1ifp1 s1c s1sfn
+step s1brr: BEGIN ISOLATION LEVEL REPEATABLE READ;
+step s1dfp: DELETE FROM fk_parted_pk WHERE a = 1;
+step s1ifp1: INSERT INTO fk_parted_pk VALUES (1);
+step s1c: COMMIT;
+step s1sfn: SELECT * FROM fk_noparted;
+a
+-
+1
+(1 row)
+
+
+starting permutation: s1brc s1dfp s1ifp1 s1c s1sfn
+step s1brc: BEGIN ISOLATION LEVEL READ COMMITTED;
+step s1dfp: DELETE FROM fk_parted_pk WHERE a = 1;
+step s1ifp1: INSERT INTO fk_parted_pk VALUES (1);
+step s1c: COMMIT;
+step s1sfn: SELECT * FROM fk_noparted;
+a
+-
+1
+(1 row)
+

src/test/isolation/isolation_schedule

@@ -33,6 +33,7 @@ test: fk-deadlock
 test: fk-deadlock2
 test: fk-partitioned-1
 test: fk-partitioned-2
+test: fk-snapshot
 test: eval-plan-qual
 test: eval-plan-qual-trigger
 test: lock-update-delete

src/test/isolation/specs/fk-snapshot.spec

@@ -0,0 +1,61 @@
+setup
+{
+  CREATE TABLE pk_noparted (
+	a			int		PRIMARY KEY
+  );
+
+  CREATE TABLE fk_parted_pk (
+	a			int		PRIMARY KEY REFERENCES pk_noparted ON DELETE CASCADE
+  ) PARTITION BY LIST (a);
+  CREATE TABLE fk_parted_pk_1 PARTITION OF fk_parted_pk FOR VALUES IN (1);
+  CREATE TABLE fk_parted_pk_2 PARTITION OF fk_parted_pk FOR VALUES IN (2);
+
+  CREATE TABLE fk_noparted (
+	a			int		REFERENCES fk_parted_pk ON DELETE NO ACTION INITIALLY DEFERRED
+  );
+  INSERT INTO pk_noparted VALUES (1);
+  INSERT INTO fk_parted_pk VALUES (1);
+  INSERT INTO fk_noparted VALUES (1);
+}
+
+teardown
+{
+  DROP TABLE pk_noparted, fk_parted_pk, fk_noparted;
+}
+
+session s1
+step s1brr	{ BEGIN ISOLATION LEVEL REPEATABLE READ; }
+step s1brc	{ BEGIN ISOLATION LEVEL READ COMMITTED; }
+step s1ifp2	{ INSERT INTO fk_parted_pk VALUES (2); }
+step s1ifp1	{ INSERT INTO fk_parted_pk VALUES (1); }
+step s1dfp	{ DELETE FROM fk_parted_pk WHERE a = 1; }
+step s1c	{ COMMIT; }
+step s1sfp	{ SELECT * FROM fk_parted_pk; }
+step s1sp	{ SELECT * FROM pk_noparted; }
+step s1sfn	{ SELECT * FROM fk_noparted; }
+
+session s2
+step s2brr	{ BEGIN ISOLATION LEVEL REPEATABLE READ; }
+step s2brc	{ BEGIN ISOLATION LEVEL READ COMMITTED; }
+step s2ip2	{ INSERT INTO pk_noparted VALUES (2); }
+step s2ifn2	{ INSERT INTO fk_noparted VALUES (2); }
+step s2c	{ COMMIT; }
+step s2sfp	{ SELECT * FROM fk_parted_pk; }
+step s2sfn	{ SELECT * FROM fk_noparted; }
+
+# inserting into referencing tables in transaction-snapshot mode
+# PK table is non-partitioned
+permutation s1brr s2brc s2ip2 s1sp s2c s1sp s1ifp2 s1c s1sfp
+# PK table is partitioned: buggy, because s2's serialization transaction can
+# see the uncommitted row thanks to the latest snapshot taken for
+# partition lookup to work correctly also ends up getting used by the PK index
+# scan
+permutation s2ip2 s2brr s1brc s1ifp2 s2sfp s1c s2sfp s2ifn2 s2c s2sfn
+
+# inserting into referencing tables in up-to-date snapshot mode
+permutation s1brc s2brc s2ip2 s1sp s2c s1sp s1ifp2 s2brc s2sfp s1c s1sfp s2ifn2 s2c s2sfn
+
+# deleting a referenced row and then inserting again in the same transaction; works
+# the same no matter the snapshot mode
+permutation s1brr s1dfp s1ifp1 s1c s1sfn
+permutation s1brc s1dfp s1ifp1 s1c s1sfn