postgresql逻辑复制的实现

新建一个库，做为订阅端
[pg@localhost data]$ pg_ctl init -D /data/db3

发布与订阅端都建相关同步结构的表t1,t2
postgres=# create table t1(id int,name varchar(20));
CREATE TABLE
postgres=# create table t2(id int,name varchar(20));
CREATE TABLE

修改发布端wal_level = logical，修改后要restart订阅端，reload不生效。
postgres=# show wal_level;
 wal_level
-----------
 logical
(1 row)


postgres=# create publication pub_test for table t1;
CREATE PUBLICATION

注：订阅端有wal_level也必须是logical

postgres=# create subscription sub_test connection 'host=127.0.0.1 port=15431 dbname=postgres user=pg' publication pub_test;
NOTICE:  created replication slot "sub_test" on publisher
CREATE SUBSCRIPTION

在发布端分别向 t1 t2表插入数据
postgres=# insert into t1(id,name) values (1,'name1');
INSERT 0 1
postgres=# insert into t2(id,name) values (1,'name1');
INSERT 0 1

查看订阅端，只有已新建订阅的表数据同步
postgres=# select * from t1;
 id | name
----+-------
  1 | name1
(1 row)

postgres=# select * from t2;
 id | name
----+------
(0 rows)

发布端，将t2加入到发布
postgres=# alter publication pub_test add table t2;
ALTER PUBLICATION

查看发布表
postgres=# select * from pg_publication_tables;
 pubname  | schemaname | tablename
----------+------------+-----------
 pub_test | public     | t1
 pub_test | public     | t2
(2 rows)

订阅端，刷新订阅配置
postgres=# alter subscription sub_test refresh publication;
ALTER SUBSCRIPTION

发布端，分别向t1 t2插入数据
postgres=# insert into t1(id,name) values (2,'name2');
INSERT 0 1
postgres=# insert into t2(id,name) values (2,'name2');
INSERT 0 1

订阅端，查看t1 t2的数据
postgres=# select * from t1;
 id | name
----+-------
  1 | name1
  2 | name2
(2 rows)

postgres=# select * from t2;
 id | name
----+-------
  1 | name1
  2 | name2
(2 rows)

T1没有主建，直接删除，提示需要设置 REPLICA IDENTITY
postgres=# delete from t1 where id=1;
ERROR:  cannot delete from table "t1" because it does not have a replica identity and publishes deletes
HINT:  To enable deleting from the table, set REPLICA IDENTITY using ALTER TABLE.

修改为full，删除成功
postgres=# alter table t1 replica identity full;
ALTER TABLE
postgres=# delete from t1 where id=1;
DELETE 1