PostgreSQL 中的postgres_fdw扩展详解

[root@107 ~]# su postgre
su: user postgre does not exist
[root@107 ~]# su postgres
bash-4.2$ psql mydb postgres
could not change directory to "/root": 权限不够
psql (10.7)
Type "help" for help.

mydb=# CREATE EXTENSION postgres_fdw;
CREATE EXTENSION

mydb=# create server fs_postgres_bbc 
foreign data wrapper postgres_fdw options(host '182.61.136.109',port '5432',dbname 'technology');
mydb=#

mydb=# create user mapping for postgres server 
fs_postgres_bbc options(user 'postgres',password 'password');
CREATE USER MAPPING
mydb=#

technology=# select * from public.customers where id < 5;
 id | name 
----+-------
 1 | name1
 2 | name2
 3 | name3
 4 | name4
(4 rows)

technology=# 
-- schemaname = public

mydb=# create foreign table ft_customers 
(
 id int4 primary key ,
 name varchar(200)
 ) server fs_postgres_bbc options (schema_name 'public',table_name 'customers');



错误: 外部表上不支持主键约束

第1行create foreign table ft_customers (id int4 primary key , nam...
            ^
mydb=#

mydb=# create foreign table ft_customers (
 id int4 , 
 name varchar(200)
) server fs_postgres_bbc options (schema_name 'public',table_name 'customers');
CREATE FOREIGN TABLE
mydb=#

mydb=# select * from ft_customers where id < 5;
 id | name 
----+-------
 1 | name1
 2 | name2
 3 | name3
 4 | name4
(4 rows)

mydb=#

create table orders (
 id int PRIMARY KEY,
 customerid int
);

INSERT INTO orders(id,customerid) VALUES(1,1),(2,2);

SELECT * FROM orders;

-- 和外部表关联查询。
mydb=# SELECT o.*,c.*
mydb-# FROM orders o
mydb-# INNER JOIN ft_customers c ON o.customerid = c.id
mydb-# WHERE c.id < 10000;
 id | customerid | id | name 
----+------------+----+-------
 1 |   1 | 1 | name1
 2 |   2 | 2 | name2
(2 rows)

mydb=#

mydb=# select count(*) from ft_customers;
 count 
----------
 10000000
(1 row)

mydb=# delete from ft_customers where id = 9999999;
DELETE 1
mydb=# select count(*) from ft_customers;
 count 
---------
 9999999
(1 row)

mydb=# insert into ft_customers values(9999999,'name1');
INSERT 0 1
mydb=# select count(*) from ft_customers;
 count 
----------
 10000000
(1 row)

mydb=# select * from ft_customers where id = 9999999;
 id | name 
---------+-------
 9999999 | name1
(1 row)

mydb=# update ft_customers set name = 'name999' where id = 9999999;
UPDATE 1
mydb=# select * from ft_customers where id = 9999999;
 id | name 
---------+---------
 9999999 | name999
(1 row)

mydb=#

mydb=# EXPLAIN(ANALYZE on,VERBOSE on) select id,count(*) from ft_customers where id < 100 group by id;
            QUERY PLAN            
----------------------------------------------------------------------------------------------------
 Foreign Scan (cost=104.88..157.41 rows=199 width=12) (actual time=16.725..16.735 rows=99 loops=1)
 Output: id, (count(*))
 Relations: Aggregate on (public.ft_customers)
 Remote SQL: SELECT id, count(*) FROM public.customers WHERE ((id < 100)) GROUP BY 1
 Planning time: 0.247 ms
 Execution time: 249.410 ms
(6 rows)

mydb=#