CREATE TABLE test_replica_identity (
       id serial primary key,
       keya text not null,
       keyb text not null,
       nonkey text,
       CONSTRAINT test_replica_identity_unique_defer UNIQUE (keya, keyb) DEFERRABLE,
       CONSTRAINT test_replica_identity_unique_nondefer UNIQUE (keya, keyb)
);
CREATE TABLE test_replica_identity_othertable (id serial primary key);
CREATE INDEX test_replica_identity_keyab ON test_replica_identity (keya, keyb);
CREATE UNIQUE INDEX test_replica_identity_keyab_key ON test_replica_identity (keya, keyb);
CREATE UNIQUE INDEX test_replica_identity_nonkey ON test_replica_identity (keya, nonkey);
CREATE INDEX test_replica_identity_hash ON test_replica_identity USING hash (nonkey);
WARNING:  hash indexes are not WAL-logged and their use is discouraged
CREATE UNIQUE INDEX test_replica_identity_expr ON test_replica_identity (keya, keyb, (3));
CREATE UNIQUE INDEX test_replica_identity_partial ON test_replica_identity (keya, keyb) WHERE keyb != '3';
-- default is 'd'/DEFAULT for user created tables
SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
 relreplident 
--------------
 d
(1 row)

-- but 'none' for system tables
SELECT relreplident FROM pg_class WHERE oid = 'pg_class'::regclass;
 relreplident 
--------------
 n
(1 row)

SELECT relreplident FROM pg_class WHERE oid = 'pg_constraint'::regclass;
 relreplident 
--------------
 n
(1 row)

----
-- Make sure we detect ineligible indexes
----
-- fail, not unique
ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX test_replica_identity_keyab;
ERROR:  cannot use non-unique index "test_replica_identity_keyab" as replica identity
-- fail, not a candidate key, nullable column
ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX test_replica_identity_nonkey;
ERROR:  index "test_replica_identity_nonkey" cannot be used as replica identity because column "nonkey" is nullable
-- fail, hash indexes cannot do uniqueness
ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX test_replica_identity_hash;
ERROR:  cannot use non-unique index "test_replica_identity_hash" as replica identity
-- fail, expression index
ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX test_replica_identity_expr;
ERROR:  cannot use expression index "test_replica_identity_expr" as replica identity
-- fail, partial index
ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX test_replica_identity_partial;
ERROR:  cannot use partial index "test_replica_identity_partial" as replica identity
-- fail, not our index
ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX test_replica_identity_othertable_pkey;
ERROR:  "test_replica_identity_othertable_pkey" is not an index for table "test_replica_identity"
-- fail, deferrable
ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX test_replica_identity_unique_defer;
ERROR:  cannot use non-immediate index "test_replica_identity_unique_defer" as replica identity
SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
 relreplident 
--------------
 d
(1 row)

----
-- Make sure index cases succeeed
----
-- succeed, primary key
ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX test_replica_identity_pkey;
SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
 relreplident 
--------------
 i
(1 row)

\d test_replica_identity
                         Table "public.test_replica_identity"
 Column |  Type   |                             Modifiers                              
--------+---------+--------------------------------------------------------------------
 id     | integer | not null default nextval('test_replica_identity_id_seq'::regclass)
 keya   | text    | not null
 keyb   | text    | not null
 nonkey | text    | 
Indexes:
    "test_replica_identity_pkey" PRIMARY KEY, btree (id) REPLICA IDENTITY
    "test_replica_identity_expr" UNIQUE, btree (keya, keyb, (3))
    "test_replica_identity_keyab_key" UNIQUE, btree (keya, keyb)
    "test_replica_identity_nonkey" UNIQUE, btree (keya, nonkey)
    "test_replica_identity_partial" UNIQUE, btree (keya, keyb) WHERE keyb <> '3'::text
    "test_replica_identity_unique_defer" UNIQUE CONSTRAINT, btree (keya, keyb) DEFERRABLE
    "test_replica_identity_unique_nondefer" UNIQUE CONSTRAINT, btree (keya, keyb)
    "test_replica_identity_hash" hash (nonkey)
    "test_replica_identity_keyab" btree (keya, keyb)

-- succeed, nondeferrable unique constraint over nonullable cols
ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX test_replica_identity_unique_nondefer;
-- succeed unique index over nonnullable cols
ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX test_replica_identity_keyab_key;
ALTER TABLE test_replica_identity REPLICA IDENTITY USING INDEX test_replica_identity_keyab_key;
SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
 relreplident 
--------------
 i
(1 row)

\d test_replica_identity
                         Table "public.test_replica_identity"
 Column |  Type   |                             Modifiers                              
--------+---------+--------------------------------------------------------------------
 id     | integer | not null default nextval('test_replica_identity_id_seq'::regclass)
 keya   | text    | not null
 keyb   | text    | not null
 nonkey | text    | 
Indexes:
    "test_replica_identity_pkey" PRIMARY KEY, btree (id)
    "test_replica_identity_expr" UNIQUE, btree (keya, keyb, (3))
    "test_replica_identity_keyab_key" UNIQUE, btree (keya, keyb) REPLICA IDENTITY
    "test_replica_identity_nonkey" UNIQUE, btree (keya, nonkey)
    "test_replica_identity_partial" UNIQUE, btree (keya, keyb) WHERE keyb <> '3'::text
    "test_replica_identity_unique_defer" UNIQUE CONSTRAINT, btree (keya, keyb) DEFERRABLE
    "test_replica_identity_unique_nondefer" UNIQUE CONSTRAINT, btree (keya, keyb)
    "test_replica_identity_hash" hash (nonkey)
    "test_replica_identity_keyab" btree (keya, keyb)

SELECT count(*) FROM pg_index WHERE indrelid = 'test_replica_identity'::regclass AND indisreplident;
 count 
-------
     1
(1 row)

----
-- Make sure non index cases work
----
ALTER TABLE test_replica_identity REPLICA IDENTITY DEFAULT;
SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
 relreplident 
--------------
 d
(1 row)

SELECT count(*) FROM pg_index WHERE indrelid = 'test_replica_identity'::regclass AND indisreplident;
 count 
-------
     0
(1 row)

ALTER TABLE test_replica_identity REPLICA IDENTITY FULL;
SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
 relreplident 
--------------
 f
(1 row)

\d+ test_replica_identity
                                             Table "public.test_replica_identity"
 Column |  Type   |                             Modifiers                              | Storage  | Stats target | Description 
--------+---------+--------------------------------------------------------------------+----------+--------------+-------------
 id     | integer | not null default nextval('test_replica_identity_id_seq'::regclass) | plain    |              | 
 keya   | text    | not null                                                           | extended |              | 
 keyb   | text    | not null                                                           | extended |              | 
 nonkey | text    |                                                                    | extended |              | 
Indexes:
    "test_replica_identity_pkey" PRIMARY KEY, btree (id)
    "test_replica_identity_expr" UNIQUE, btree (keya, keyb, (3))
    "test_replica_identity_keyab_key" UNIQUE, btree (keya, keyb)
    "test_replica_identity_nonkey" UNIQUE, btree (keya, nonkey)
    "test_replica_identity_partial" UNIQUE, btree (keya, keyb) WHERE keyb <> '3'::text
    "test_replica_identity_unique_defer" UNIQUE CONSTRAINT, btree (keya, keyb) DEFERRABLE
    "test_replica_identity_unique_nondefer" UNIQUE CONSTRAINT, btree (keya, keyb)
    "test_replica_identity_hash" hash (nonkey)
    "test_replica_identity_keyab" btree (keya, keyb)
Replica Identity: FULL

ALTER TABLE test_replica_identity REPLICA IDENTITY NOTHING;
SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
 relreplident 
--------------
 n
(1 row)

DROP TABLE test_replica_identity;
DROP TABLE test_replica_identity_othertable;