Kingbase_FDW 使用介绍
与postgresql_fdw功能类似,KINGBASE_FDW 是一种外部访问接口,它可以被用来访问存储在外部的数据。想要使用fdw访问数据需要先确保:网络通,数据库访问配置(pg_hba,conf)正常,同时远端数据库的用户必须有表的相关权限。
一、远程数据库
远程数据库 IP: 142 。创建用户及测试数据:
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create role user_remote with login; alter role user_remote with password 'user_remote' ; create schema user_remote authorization user_remote; \c test user_remote create table t1(id integer , name varchar (9)); insert into t1 values (1, 'a' ),(2, 'b' ); |
二、本地数据库
本地数据库 IP: 143
1、创建扩展 kingbase_fdw
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\c test system create role user_local with login; alter role user_local with password 'user_local' ; create schema user_local authorization user_local; create extension kingbase_fdw; |
扩展创建完成后,pg_foreign_data_wrapper 有如下一行:
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test=# select * from pg_foreign_data_wrapper where fdwname= 'kingbase_fdw' ; oid | fdwname | fdwowner | fdwhandler | fdwvalidator | fdwacl | fdwoptions -------+--------------+----------+------------+--------------+--------+------------ 16495 | kingbase_fdw | 10 | 16493 | 16494 | | (1 row) |
2、create server
create server <server名称> foreign data wrapper postgres_fdw options (host '<远程数据库主机名>’, port '<远程数据库端口>', dbname '<远程数据库名称>');
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create server srv_42 foreign data wrapper kingbase_fdw options(host '192.168.237.42' ,port '54321' ,dbname 'test' ); grant usage on foreign server srv_42 to user_local; |
注意:必须将 Server 授权给用户,否则用户在创建外部表时,会报“ERROR: permission denied for foreign server srv_42” 错误。创建完server后,在sys_foreign_server 会有如下一条:
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test=> select * from sys_foreign_server where srvname= 'srv_42' ; oid | srvname | srvowner | srvfdw | srvtype | srvversion | srvacl | srvoptions -------+---------+----------+--------+---------+------------+---------------------------------------+---------------------------------------------- 16502 | srv_42 | 10 | 16495 | | | {system=U/system,user_local=U/system} | {host=192.168.237.42,port=54321,dbname=test} (1 row) |
3、创建user mapping
create user mapping for <本地数据库用户>
server <server名称>
options (user '<远程数据库用户>', password '<远程数据库用户密码>');
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create user mapping for user_local server srv_42 options( user 'user_remote' , password 'user_remote' ); |
创建后,在pg_user_mappings 会有一条记录:
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test=> select * from pg_user_mappings where srvname= 'srv_42' ; umid | srvid | srvname | umuser | usename | umoptions -------+-------+---------+--------+------------+----------------------------------------- 16503 | 16502 | srv_42 | 16500 | user_local | { user =user_remote, password =user_remote} |
4、创建外部表
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create foreign table ft_t1 ( id integer , name varchar (9) ) server srv_42 options (schema_name 'user_remote' ,table_name 't1' ); |
5、访问测试
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test=> \d List of relations Schema | Name | Type | Owner ------------+-------+---------------+------------ user_local | ft_t1 | foreign table | user_local (1 row) test=> select * from ft_t1; id | name ----+----------- 1 | a 2 | b (2 rows ) |
6、选择导入远程的整个schema
可以将远程schema下的所有表及视图通过import 方式导入,避免逐表创建。
import foreign schema <远程数据库schema名称>
from <server名称>
into <本地数据库schema名称>;
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test=> import foreign schema user_remote from server srv_42 into user_local; IMPORT FOREIGN SCHEMA test=> \d List of relations Schema | Name | Type | Owner ------------+------+---------------+------------ user_local | t1 | foreign table | user_local user_local | t2 | foreign table | user_local |
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