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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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