pgsql_fdw

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是一个类似dblink的一个跨库操作的中间件。

1：环境：

本地库：

ip：127.0.0.1

port：5432

dbname：postgres

外部库：
ip：127.0.0.1

port：5001

dbname：digoal

本地库postgres信息：

postgres=# select * from pg_stat_activity;

-[ RECORD 1 ]----+--------------------------------

datid | 12896

datname | postgres

pid | 39391

usesysid | 10

usename | postgres

application_name | psql

client_addr | ::1

client_hostname |

client_port | 57313

backend_start | 2014-06-09 10:11:39.697793+08

xact_start | 2014-06-09 10:55:19.629726+08

query_start | 2014-06-09 10:55:19.629726+08

state_change | 2014-06-09 10:55:19.629749+08

waiting | f

state | active

query | select * from pg_stat_activity;

外部库digoal信息：

digoal=# select * from pg_stat_activity;

-[ RECORD 1 ]----+--------------------------------

datid | 16384

datname | digoal

pid | 39570

usesysid | 10

usename | postgres

application_name | psql

client_addr | ::1

client_hostname |

client_port | 42339

backend_start | 2014-06-09 10:51:28.05419+08

xact_start | 2014-06-09 10:52:46.52235+08

query_start | 2014-06-09 10:52:46.52235+08

state_change | 2014-06-09 10:52:46.522354+08

waiting | f

state | active

query | select * from pg_stat_activity;

2：在外部数据库创建表

CREATE table test ( id int,info text);

digoal=# insert  into  test values(1,'xxxx');
INSERT 0 1

3：本地配置：

需先create extension postgres_fdw;创建此中间件。

1：CREATE SERVER

define a new foreign server

CREATE SERVER server_name [ TYPE 'server_type' ] [ VERSION 'server_version' ]
FOREIGN DATA WRAPPER fdw_name
[ OPTIONS ( option 'value' [, ... ] ) ]

fdw_name：必须是creaete extension ...安装过的，比如“pgsql”，“file_fdw”，“plproxy”......

postgres=# create extension postgres_fdw ;
CREATE EXTENSION
postgres=# CREATE SERVER myserver FOREIGN DATA WRAPPER postgres_fdw OPTIONS (host 'localhost', dbname 'digoal', port '5001');
CREATE SERVER

2：CREATE USER MAPPING

define a new mapping of a user to a foreign server

CREATE USER MAPPING FOR { user_name | USER | CURRENT_USER | PUBLIC }
SERVER server_name
[ OPTIONS ( option 'value' [ , ... ] ) ]

user_name：本地数据库用户名。

server_name：是在上一步通过create server创建的名字。

options：远程数据库端的信息。

postgres=# CREATE USER MAPPING FOR postgres SERVER myserver OPTIONS (user 'postgres', password '***');
CREATE USER MAPPING

postgres=# \deu+
List of user mappings
-[ RECORD 1 ]------------------------------------
Server      | myserver
User name   | postgres
FDW Options | ("user" 'postgres', password '***')

3：CREATE FOREIGN TABLE

CREATE FOREIGN TABLE test ( id int,info text) server myserver  options (schema_name 'public', table_name 'test');

如果去掉options的选项，则会自动在外部数据库中找到相应表。

4：在本地查看外部数据表

postgres=# select * from test;
id | info
----+------
1 | xxxx
(1 row)

4：在本地库清理

1：删除foreign table：

postgres=# drop foreign table test;
DROP FOREIGN TABLE

2：删除mapping：

postgres=# \deu+
List of user mappings
Server  | User name |             FDW Options
----------+-----------+-------------------------------------
myserver | postgres  | ("user" 'postgres', password '***')
(1 row)

postgres=# DROP USER MAPPING IF EXISTS FOR postgres SERVER myserver;
DROP USER MAPPING

3：删除server：

postgres=# drop server myserver ;
DROP SERVER