PostgreSQL数据库中跨库访问解决方案
PostgreSQL跨库访问有3种方法：Schema，dblink，postgres_fdw。
方法A：在PG上建立不同SCHEMA，将数据和存储过程分别放到不同的schema上，经过权限管理后进行访问。
方法A的示例如下：
测试1（测试postgres超级用户对不同schema下对象的访问）
查看当前数据库中的schema
postgres=# \dn
List of schemas
Name | Owner
-------------------+---------
dbms_job_procedure | postgres pgagent | postgres
postgres | postgres
public | postgres
(4 rows)
（当前连接数据库的用户为postgres）
postgres=# select user;
user
----------
postgres
(1 row)
创建名为test1的schema
postgres=# create schema test1;
CREATE SCHEMA
创建模式test1下的对象，表ticket1
postgres=# create table test1.ticket1(id int);
CREATE TABLE
可以看到并没有我们之前建立的表
postgres=# \d
List of relations
Schema | Name | Type | Owner
-------------------------+---------
public | dept | table | postgres
public | emp | table | postgres
public | jobhist | table | postgres
public | next_empno | sequence | postgres
public | salesemp | view | postgres
(5 rows)
在对象前加schema，postgres用户可以访问ticket1表
postgres=# select * from test1.ticket1;
id
-------------------------------------------------
(0 rows)
查看模式 搜索路径
postgres=# show search_path ;
search_path
----------------
"$user",public
(1 row)
把创建的模式test1添加到模式搜索路径
postgres=# set search_path to "$user",public,test1;
SET
postgres=# show search_path ;
search_path
------------------------
"$user", public, test1
(1 row)
为了访问方便，在搜索路径中添加schema对象之后既可以看到该模式下的表，也可以直接进行搜索，而不用添加schema前缀。（这里因为是超级用户，所以不用给postgres赋权，如果是普通用户，想要访问，需要赋权）
postgres=# \d
List of relations
Schema | Name | Type | Owner
-------------------------+---------
public | dept | table | postgres
public | emp | table | postgres
public | jobhist | table | postgres
public | next_empno | sequence | postgres
public | salesemp | view | postgres
test1 | ticket1 | table | postgres
(6 rows)
postgres=# select * from ticket1;
id
--------------------------------------------
(0 rows)
测试2：
在postgres用户下建立名为test2的schema
postgres=# create schema test2;
CREATE SCHEMA
postgres=# create table test2.ticket2(id int);
CREATE TABLE
建立两个普通用户
postgres=# create role test1 login password '123';
CREATE ROLE
postgres=# create role test2 login password '123';
CREATE ROLE
普通用户连接数据库
postgres=# \c postgres test2;
Password for user test2:
You are now connected to database "postgres" as user "test2".
postgres=> \d
List of relations
Schema | Name | Type | Owner
-------------------------+---------
public | dept | table | postgres
public | emp | table | postgres
public | jobhist | table | postgres
public | next_empno | sequence | postgres
public | salesemp | view | postgres
(5 rows)
postgres=> show search_path ;
search_path
----------------
"$user",public
(1 row)
postgres=> set search_path to "$user",public,test1;
SET
postgres=> \d
List of relations
Schema | Name | Type | Owner
-------------------------+---------
public | dept | table | postgres
public | emp | table | postgres
public | jobhist | table | postgres
public | next_empno | sequence | postgres
public | salesemp | view | postgres
test1 | ticket1 | table | postgres
test2 | ticket2 | table | postgres
(11 rows)
可以看到test2用户模式下的ticket2表，但是访问时权限不足。
postgres=> select * from test2.ticket2;
ERROR: permission denied for relation ticket2
postgres=> select * from ticket2;
ERROR: permission denied for relation ticket2
通过postgres超级用户赋予权限，即可访问
postgres=# grant select on all tables in schema test2 to test1;
GRANT
postgres=> select * from test2.ticket2;
id
---------------------------------------------------
(0 rows)
postgres=> select * from ticket2;
id
---------------------------------------------------
(0 rows)
方法B：通过dblink实现跨库访问
方法B测试示例如下：
环境：本地：192.168.56.88 数据库：postgres
远程：192.168.56.99 数据库：test
PostgreSQL通过dblink实现跨库访问
测试1：在同一个实例下分别建立两个数据库，通过dblink 实现跨库访问
postgres=# create database test;
CREATE DATABASE
postgres=# \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+----------+----------+---------+-------+-----------------------
postgres | postgres | UTF8 | C | C |
template0 | postgres | UTF8 | C | C | =c/postgres +
| | | | | postgres=CTc/postgres
template1 | postgres | UTF8 | C | C | =c/postgres +
| | | | | postgres=CTc/postgres
test | postgres | UTF8 | C | C |
(4 rows)
postgres=# \c test
You are now connected to database "test" as user "postgres".
test=# create table test(id int);
CREATE TABLE
test=# \d
List of relations
Schema | Name | Type | Owner
--------+------+-------+----------
public | test | table | postgres
(1 row)
test=# create table test2(id int);
CREATE TABLE
test=# insert into test values ('1111');
INSERT 0 1
test=# \c postgres
You are now connected to database "postgres" as user "postgres".
在postgres数据库中建立dblink连接到test数据库
postgres=# create extension dblink;
CREATE EXTENSION
postgres=# select * from pg_extension;
extname | extowner | extnamespace | extrelocatable | extversion | extconfig | extcondition
---------+----------+--------------+----------------+------------+-----------+--------------
plpgsql | 10 | 11 | f | 1.0 | |
dblink | 10 | 2200 | t | 1.1 | |
(2 rows)
postgres=# select dblink_connect('test_dblink','dbname=test host=localhost port=5432 user=postgres password=postgres');
dblink_connect
----------------
OK
(1 row)
postgres=# select * from dblink('test_dblink','select * from test') as t1(id int);
id
------
1111
(1 row)
通过建立dblink，在postgres数据库可以很容易的访问到test数据库中的数据。
为了访问test数据库中的数据方便，我们可以建立一个视图，操作如下，我们只需要查询视图中的内容即可。
postgres=# CREATE VIEW testdb_dblink AS
postgres-# SELECT * FROM dblink('hostaddr=127.0.0.1 port=5432 dbname=test user=postgres password=postgres', 'SELECT * From test') AS t(id int);
CREATE VIEW
postgres=# \d
List of relations
Schema | Name | Type | Owner
--------+-------------------------+-------+----------
public | ptest1 | table | postgres
public | ptest2 | table | postgres
public | remote_people_user_name | view | postgres
public | testdb_dblink | view | postgres
(4 rows)
postgres=# select * from testdb_dblink ;
id
------
1111
(1 row)
测试2：
在两个实例下分别创建数据库，然后通过dblink实现垮库访问。
实例1：
首先需要配置下路由配置，添加一行命令-A INPUT -s 192.168.0.0/16 -j ACCEPT
[root@darry etc]# vi /etc/sysconfig/iptables
...
添加-A INPUT -s 192.168.0.0/16 -j ACCEPT 即允许192.168.0.0的网段访问
....
[root@darry etc]# service iptables reload
iptables: Trying to reload firewall rules: [ OK ]
在IP为192.168.56.88（本地）的postgres数据库中建立extension
postgres=# create extension dblink;
CREATE EXTENSION
postgres=# select * from pg_extension;
extname | extowner | extnamespace | extrelocatable | extversion | extconfig | extcondition
---------+----------+--------------+----------------+------------+-----------+--------------
plpgsql | 10 | 11 | f | 1.0 | |
dblink | 10 | 2200 | t | 1.1 | |
(2 rows)
建立dblink 访问IP为192.168.56.99（远程）数据库
postgres=# select dblink_connect('test_dblink','dbname=test host=192.168.56.99 port=5432 user=postgres password=postgres');
dblink_connect
----------------
OK
(1 row)
postgres=# select * from dblink('test_dblink','select * from test') as t1(id int);
id
------
1111
(1 row)
跨库事务测试
连接远程数据库
postgres=# select dblink_connect('test_dblink','dbname=test host=192.168.56.99 port=5432 user=postgres password=postgres');
dblink_connect
----------------
OK
(1 row)
在远程服务器上开始一个事务
postgres=# select dblink_exec('test_dblink','begin;');
dblink_exec
-------------
BEGIN
(1 row)
插入一条数据
postgres=# select dblink_exec('test_dblink','insert into test values(7777);');
dblink_exec
-------------
INSERT 0 1
(1 row)
经查看远程服务器上已经插入一条数据
postgres=# select * from dblink('test_dblink','select * from test') as t1(id int);
id
-------
1111
2222
3333
4444
6666
33333
7777
(11 rows)
在远程数据库中查看未发现数据，因为事务未提交
test=# select * from test;
id
-------
1111
2222
3333
4444
6666
33333
在本地数据库中提交远程连接数据库中的事务
postgres=# select dblink_exec('test_dblink','commit;');
dblink_exec
-------------
COMMIT
(1 row)
再次查看
postgres=# select * from dblink('test_dblink','select * from test') as t1(id int);
id
-------
1111
2222
3333
4444
6666
33333
7777
远程数据库中也存在
test=# select * from test;
id
-------
1111
2222
3333
4444
6666
33333
7777
若换成将commit替换成rollback则插入取消
postgres=# select dblink_exec('test_dblink','begin;');
dblink_exec
-------------
BEGIN
(1 row)
postgres=# select dblink_exec('test_dblink','insert into test values(99999);');
dblink_exec
-------------
INSERT 0 1
postgres=# select * from dblink('test_dblink','select * from test') as t1(id int);
id
-------
1111
2222
3333
4444
6666
33333
7777
99999
执行回滚操作
postgres=# select dblink_exec('test_dblink','rollback;');
dblink_exec
-------------
ROLLBACK
(1 row)
经查看回滚之后，不记录之前插入的数据
postgres=# select * from dblink('test_dblink','select * from test') as t1(id int);
id
-------
1111
2222
3333
4444
6666
33333
7777
方法C：通过postgres_fdw实现跨库访问
环境：本地：192.168.0.14，远程：192.168.0.17，PG：9.3.9两台机器的测试用户及数据库均为：test,test
1.在本地数据库中创建postgres_fdw extension.
[postgres@minion1 bin]$ ./psql test test
psql (9.3.9)
Type "help" for help.
test=# \c test test
You are now connected to database "test" as user "test".
test=# create extension postgres_fdw ;
CREATE EXTENSION
2.在远程数据库上生成测试数据 :
[postgres@minion4 bin]$ ./psql test test
psql (9.3.9)
Type "help" for help.
test=# CREATE TYPE user_enum AS ENUM ('foo', 'bar', 'buz');
CREATE TYPE
test=# \dT
List of data types
Schema | Name | Description
--------+-----------+-------------
public | user_enum |
(1 row)
test=# select oid from pg_type where typname='user_enum';
oid
-------
16902
(1 row)
test=# CREATE SCHEMA test;
CREATE SCHEMA
test=# CREATE TABLE test.test1 (
test(# c1 int NOT NULL,
test(# c2 int NOT NULL,
test(# c3 text,
test(# c4 timestamptz,
test(# c5 timestamp,
test(# c6 varchar(10),
test(# c7 char(10),
test(# c8 user_enum,
test(# CONSTRAINT t1_pkey PRIMARY KEY (c1)
test(# );
CREATE TABLE
test=# CREATE TABLE test.test2 (
test(# c1 int NOT NULL,
test(# c2 text,
test(# CONSTRAINT t2_pkey PRIMARY KEY (c1)
test(# );
CREATE TABLE
test=# INSERT INTO test.test1
test-# SELECT id,
test-# id % 10,
test-# to_char(id, 'FM00000'),
test-# '1970-01-01'::timestamptz + ((id % 100) || ' days')::interval,
test-# '1970-01-01'::timestamp + ((id % 100) || ' days')::interval,
test-# id % 10,
test-# id % 10,
test-# 'foo'::user_enum
test-# FROM generate_series(1, 1000) id;
INSERT 0 1000
test=# INSERT INTO test.test2
test-# SELECT id,
test-# 'AAA' || to_char(id, 'FM000')
test-# FROM generate_series(1, 100) id;
INSERT 0 100
test=# analyze test.test1;
ANALYZE
test=# analyze test.test2;
ANALYZE
3.在本地数据库中创建server
test=# CREATE SERVER s1 FOREIGN DATA WRAPPER postgres_fdw;
CREATE SERVER
test=# select * from pg_foreign_server ;
srvname | srvowner | srvfdw | srvtype | srvversion | srvacl | srvoptions
---------+----------+--------+---------+------------+--------+------------
s1 | 17444 | 17449 | | | |
(1 row)
test=# alter server s1 options ( add hostaddr '192.168.0.17', add port '5432', add dbname 'test');
ALTER SERVER
4.SERVER赋权 :
test=# grant usage on foreign server s1 to test;
GRANT
test=# select * from pg_foreign_server ;
srvname | srvowner | srvfdw | srvtype | srvversion | srvacl | srvoptions
---------+----------+--------+---------+------------+---------------+--------------------------------
---------------
s1 | 17444 | 17449 | | | {test=U/test} | {hostaddr=192.168.0.17,port=543
2,dbname=test}
(1 row)
5.在本地数据库中创建user mapping :
test=# create user mapping for test server s1 options(user 'test',password 'test');
CREATE USER MAPPING
6.在本地数据库中创建foreign table
test=# CREATE TYPE user_enum AS ENUM ('foo', 'bar', 'buz');
CREATE TYPE
test=# \dT
List of data types
Schema | Name | Description
--------+-----------+-------------
public | user_enum |
(1 row)
test=# select oid from pg_type where typname='user_enum';
oid
-------
17453
(1 row)
test=# CREATE FOREIGN TABLE ft1 (
test(# c0 int,
test(# c1 int NOT NULL,
test(# c2 int NOT NULL,
test(# c3 text,
test(# c4 timestamptz,
test(# c5 timestamp,
test(# c6 varchar(10),
test(# c7 char(10),
test(# c8 user_enum
test(# ) SERVER s1 options(schema_name 'test', table_name 'test1');
CREATE FOREIGN TABLE
test=# select * from ft1 limit 1;
ERROR: column "c0" does not exist
CONTEXT: Remote SQL command: SELECT c0, c1, c2, c3, c4, c5, c6, c7, c8 FROM test.test1
test=# alter foreign table ft1 drop column c0;
ALTER FOREIGN TABLE
test=# select * from ft1 limit 1;
c1 | c2 | c3 | c4 | c5 | c6 | c7 | c8
----+----+-------+------------------------+---------------------+----+------------+-----
1 | 1 | 00001 | 1970-01-02 00:00:00+08 | 1970-01-02 00:00:00 | 1 | 1 | foo
(1 row)
test=# create foreign table ft2 (c2 text,c1 int not null) server s1 options(schema_name 'test',table_name 'test2');
CREATE FOREIGN TABLE
test=# select * from ft2 limit 1;
c2 | c1
--------+----
AAA001 | 1
(1 row)
test=# create foreign table ft3(c2 text,c3 int not null) server s1 options(schema_name 'test',table_name 'test2');
CREATE FOREIGN TABLE
test=# select * from ft3 limit 1;
ERROR: column "c3" does not exist
CONTEXT: Remote SQL command: SELECT c2, c3 FROM test.test2
test=# alter foreign table ft3 alter column c3 options (column_name 'c1');
ALTER FOREIGN TABLE
test=# select * from ft3 limit 1;
c2 | c3
--------+----
AAA001 | 1
(1 row)
test=# create foreign table ft4(c2 text,c3 int options (column_name 'c1') not null) server s1 options(schema_name 'test',table_name 'test2');
CREATE FOREIGN TABLE
test=# select * from ft4 limit 2;
c2 | c3
--------+----
AAA001 | 1
AAA002 | 2
(2 rows)
PostgreSQL跨库访问事务测试
远程机器创建测试表
test=# create table test3(id int);
CREATE TABLE
test=# select * from test3;
id
----
(0 rows)
本地机器测试
创建对应的外部表
test=# create foreign table ft_test3(id int) server s1 options(schema_name 'test',table_name 'test3');
CREATE FOREIGN TABLE
test=# select * from ft_test3 ;
id
----
(0 rows)
本地机器事务测试（不提交）
test=# begin;
BEGIN
test=# insert into ft_test3 values (100);
INSERT 0 1
test=# insert into ft_test3 values (200);
INSERT 0 1
test=# insert into ft_test3 values (300);
INSERT 0 1
test=# select * from ft_test3 ;
id
-----
100
200
300
(3 rows)
test=# rollback;
ROLLBACK
test=# select * from ft_test3 ;
id
----
(0 rows)
本地机器事务测试（提交）
test=# begin;
BEGIN
test=# insert into ft_test3 values (1000);
INSERT 0 1
test=# insert into ft_test3 values (2000);
INSERT 0 1
test=# insert into ft_test3 values (3000);
INSERT 0 1
test=# end;
COMMIT
test=# select * from ft_test3 ;
id
------
1000
2000
3000
(3 rows)
test=# rollback;
NOTICE: there is no transaction in progress
ROLLBACK
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