主要SQL语句
（来自PostgreSQL 10.3）
创建server
create server server_remote1 FOREIGN data wrapper postgres_fdw
OPTIONS(host '127.0.0.1', port '55100', dbname 'db1');
创建user mapping
create user mapping for wln server server_remote options(user 'wln',password 'password');
创建源表， 在 db1 中创建 表 t1：
create table t1(id1 int);
insert into t1 select generate_series(1,10);
创建外表
CREATE FOREIGN TABLE t_resource (id1 int) server server_remote options (table_name 't1');
测试
postgres=# select * from pg_foreign_server ;
srvname | srvowner | srvfdw | srvtype | srvversion | srvacl | srvoptions
---------------+----------+--------+---------+------------+--------+----------------------------------------
server_remote | 10 | 24639 | | | | {host=127.0.0.1,port=55100,dbname=db1}
(1 row)
postgres=# select * from pg_foreign_data_wrapper ;
fdwname | fdwowner | fdwhandler | fdwvalidator | fdwacl | fdwoptions
--------------+----------+------------+--------------+--------+------------
postgres_fdw | 10 | 24637 | 24638 | |
(1 row)
postgres=# explain verbose select * from t_resource ;
QUERY PLAN
----------------------------------------------------------------------------
Foreign Scan on public.t_resource (cost=100.00..197.75 rows=2925 width=4)
Output: id1
Remote SQL: SELECT id1 FROM public.t2
(3 rows)
postgres=# explain verbose update t_resource set id1 = id1*10 where id1 <2;
QUERY PLAN
------------------------------------------------------------------------------------
Update on public.t_resource (cost=100.00..158.18 rows=803 width=10)
-> Foreign Update on public.t_resource (cost=100.00..158.18 rows=803 width=10)
Remote SQL: UPDATE public.t1 SET id1 = (id1 * 10) WHERE ((id1 < 2))
(3 rows)
postgres=# explain verbose insert into t_resource values(12);
QUERY PLAN
---------------------------------------------------------------
Insert on public.t_resource (cost=0.00..0.01 rows=1 width=4)
Remote SQL: INSERT INTO public.t1(id1) VALUES ($1)
-> Result (cost=0.00..0.01 rows=1 width=4)
Output: 12
(4 rows)
问题
创建和普通表同名的外表，会产生死循环。
参考
https://www.postgresql.org/docs/current/static/postgres-fdw.html
https://yq.aliyun.com/articles/51199?spm=5176.100239.blogcont3074.10.d6nVdg
https://my.oschina.net/Kenyon/blog/214953