posgresql postgres_fdw使用

一个业务由于需要跨库访问表，选择使用外部表效率高一些，这里记录一下

这里是avcp_bill库访问avcp_work库里的相关表，这里用户名和数据库名一致

> \c avcp_bill postgres
You are now connected to database "avcp_bill" as user "postgres".
建立extension
# create extension postgres_fdw;
CREATE EXTENSION
# select * from pg_extension ;
 extname | extowner | extnamespace | extrelocatable | extversion | extconfig | extcondition 
--------------+----------+--------------+----------------+------------+-----------+--------------
 plpgsql | 10 | 11 | f | 1.0 | | 
 postgres_fdw | 10 | 2200 | t | 1.0 | | 
(2 rows)

# select * from pg_foreign_data_wrapper;
 fdwname | fdwowner | fdwhandler | fdwvalidator | fdwacl | fdwoptions 
--------------+----------+------------+--------------+--------+------------
 postgres_fdw | 10 | 3253178 | 3253179 | | 
(1 row)

# \dx
 List of installed extensions
 Name | Version | Schema | Description 
--------------+---------+------------+----------------------------------------------------
 plpgsql | 1.0 | pg_catalog | PL/pgSQL procedural language
 postgres_fdw | 1.0 | public | foreign-data wrapper for remote PostgreSQL servers
(2 rows)

赋予avcp_bill使用权限
# grant usage on foreign data wrapper postgres_fdw to avcp_bill;
#\c avcp_bill avcp_bill

创建server
# create server avcp_work_fdw foreign data wrapper postgres_fdw options(host '127.0.0.1',port '6789',dbname 'avcp_work');

创建user mapping
# CREATE USER MAPPING FOR public SERVER avcp_work_fdw OPTIONS (user 'avcp_work', password 'xxxxx');
# select * from pg_user_mappings;
 umid | srvid | srvname | umuser | usename | umoptions 
---------+---------+---------------+--------+---------+------------------------------------------------
 3253183 | 3253181 | avcp_work_fdw | 0 | public | {user=avcp_work,password=xxxxxx}
 创建相关外部表
 CREATE FOREIGN TABLE avcp_user_recharge_log_fdw (
 id integer DEFAULT nextval('avcp_user_recharge_log_id_seq'::regclass) NOT NULL,
 pay_orderid character varying,
 paytype integer DEFAULT 0 NOT NULL,
 error_message character varying,
 pointid integer DEFAULT 0 NOT NULL,
 imsi character varying(30),
 et character varying(30),
 create_time timestamp without time zone DEFAULT now() NOT NULL,
 charge_point character varying,
 channel_id character varying,
 user_price integer DEFAULT 0 NOT NULL,
 roomid integer,
 seqid bigint,
 transationid character varying,
 smsc character varying(20),
 dexid character varying,
 dexver character varying,
 card_type integer,
 provice_id integer,
 user_id character varying(200),
 seqid_str character varying(30),
 imei character varying(30)
) server avcp_work_fdw options (schema_name 'avcp_work',table_name 'avcp_user_recharge_log');

相关报错处理：
ERROR: relation "avcp_user_recharge_log_id_seq" does not exist

序列不存在，无法成功建立外部表，那么我们建立序列：
>create sequence avcp_user_recharge_log_id_seq;

> select * from avcp_pay_order_log_fdw limit 1;
ERROR: password is required
DETAIL: Non-superuser cannot connect if the server does not request a password.
HINT: Target server's authentication method must be changed

由于默认是trust，但是我们外部表的连接需要密码，所以加入以下MD5验证，reload即可。

# IPv4 local connections:
host avcp_work avcp_work 127.0.0.1/32 md5
host all all 127.0.0.1/32 trust


pg_ctl -D $PGDATA reload