Preserve replica identity index across ALTER TABLE rewrite

If an index was explicitly set as replica identity index, this setting
was lost when a table was rewritten by ALTER TABLE.  Because this
setting is part of pg_index but actually controlled by ALTER
TABLE (not part of CREATE INDEX, say), we have to do some extra work
to restore it.

Based-on-patch-by: Quan Zongliang <quanzongliang@gmail.com>
Reviewed-by: Euler Taveira <euler.taveira@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/c70fcab2-4866-0d9f-1d01-e75e189db342@gmail.com

2 files changed, 67 insertions, 0 deletions

diff --git a/src/test/regress/expected/replica_identity.out b/src/test/regress/expected/replica_identity.out
index 67c34a92a4e..65c7c9ac9f8 100644
--- a/src/test/regress/expected/replica_identity.out
+++ b/src/test/regress/expected/replica_identity.out
@@ -186,5 +186,51 @@ SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
  n
 (1 row)
 
+---
+-- Test that ALTER TABLE rewrite preserves nondefault replica identity
+---
+-- constraint variant
+CREATE TABLE test_replica_identity2 (id int UNIQUE NOT NULL);
+ALTER TABLE test_replica_identity2 REPLICA IDENTITY USING INDEX test_replica_identity2_id_key;
+\d test_replica_identity2
+       Table "public.test_replica_identity2"
+ Column |  Type   | Collation | Nullable | Default 
+--------+---------+-----------+----------+---------
+ id     | integer |           | not null | 
+Indexes:
+    "test_replica_identity2_id_key" UNIQUE CONSTRAINT, btree (id) REPLICA IDENTITY
+
+ALTER TABLE test_replica_identity2 ALTER COLUMN id TYPE bigint;
+\d test_replica_identity2
+      Table "public.test_replica_identity2"
+ Column |  Type  | Collation | Nullable | Default 
+--------+--------+-----------+----------+---------
+ id     | bigint |           | not null | 
+Indexes:
+    "test_replica_identity2_id_key" UNIQUE CONSTRAINT, btree (id) REPLICA IDENTITY
+
+-- straight index variant
+CREATE TABLE test_replica_identity3 (id int NOT NULL);
+CREATE UNIQUE INDEX test_replica_identity3_id_key ON test_replica_identity3 (id);
+ALTER TABLE test_replica_identity3 REPLICA IDENTITY USING INDEX test_replica_identity3_id_key;
+\d test_replica_identity3
+       Table "public.test_replica_identity3"
+ Column |  Type   | Collation | Nullable | Default 
+--------+---------+-----------+----------+---------
+ id     | integer |           | not null | 
+Indexes:
+    "test_replica_identity3_id_key" UNIQUE, btree (id) REPLICA IDENTITY
+
+ALTER TABLE test_replica_identity3 ALTER COLUMN id TYPE bigint;
+\d test_replica_identity3
+      Table "public.test_replica_identity3"
+ Column |  Type  | Collation | Nullable | Default 
+--------+--------+-----------+----------+---------
+ id     | bigint |           | not null | 
+Indexes:
+    "test_replica_identity3_id_key" UNIQUE, btree (id) REPLICA IDENTITY
+
 DROP TABLE test_replica_identity;
+DROP TABLE test_replica_identity2;
+DROP TABLE test_replica_identity3;
 DROP TABLE test_replica_identity_othertable;
diff --git a/src/test/regress/sql/replica_identity.sql b/src/test/regress/sql/replica_identity.sql
index 3d2171c7336..5277ff39cd3 100644
--- a/src/test/regress/sql/replica_identity.sql
+++ b/src/test/regress/sql/replica_identity.sql
@@ -79,5 +79,26 @@ SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
 ALTER TABLE test_replica_identity REPLICA IDENTITY NOTHING;
 SELECT relreplident FROM pg_class WHERE oid = 'test_replica_identity'::regclass;
 
+---
+-- Test that ALTER TABLE rewrite preserves nondefault replica identity
+---
+
+-- constraint variant
+CREATE TABLE test_replica_identity2 (id int UNIQUE NOT NULL);
+ALTER TABLE test_replica_identity2 REPLICA IDENTITY USING INDEX test_replica_identity2_id_key;
+\d test_replica_identity2
+ALTER TABLE test_replica_identity2 ALTER COLUMN id TYPE bigint;
+\d test_replica_identity2
+
+-- straight index variant
+CREATE TABLE test_replica_identity3 (id int NOT NULL);
+CREATE UNIQUE INDEX test_replica_identity3_id_key ON test_replica_identity3 (id);
+ALTER TABLE test_replica_identity3 REPLICA IDENTITY USING INDEX test_replica_identity3_id_key;
+\d test_replica_identity3
+ALTER TABLE test_replica_identity3 ALTER COLUMN id TYPE bigint;
+\d test_replica_identity3
+
 DROP TABLE test_replica_identity;
+DROP TABLE test_replica_identity2;
+DROP TABLE test_replica_identity3;
 DROP TABLE test_replica_identity_othertable;