Foreign data wrapper in postgres

A running application can have multiple database integrated environment to send receive data. Some time multiple database of Postgres or sometimes other database like sql server/mysql/mongodb. Every database have different-different feature to integrate. Like sql server have Linked Server, mysql have Data federation Postgres have foreign data wrapper. This post is related to Postgres's foreign data wrapper.

What is foreign data wrapper in Postgres ?
How to access table from other database in Postgres ?

Postgres have a  different feature which lets you to create a foreign data wrapper inside Postgres, which lets you feel the object of current connected database. It will help to create object that will part of foreign data or database. So we can easily integrated data. This feature is called foreign data wrapper.

What are the components of foreign data wrapper ?

1. Foreign Data wrapper Extension { file_fdw , postgres_fdw }
2. Foreign database server location
3. User Mapping local and remote.
4. Schema Creation and Import.

How to create and deploy on production environment ?

1. First of all Create or enable data wrapper extension using below command.

CREATE EXTENSION postgres_fdw;

2. Now configure foreign server which is target location.

CREATE SERVER foreign_server
        FOREIGN DATA WRAPPER postgres_fdw
        OPTIONS (host 'localhost', port '5432', dbname 'ttt');

3. Now create and map local user with foregin server
       
        CREATE USER MAPPING FOR postgres
        SERVER foreign_server
        OPTIONS (user 'postgres', password 'hrhk');
       
        CREATE USER MAPPING FOR postgres
        SERVER foreign_server
        OPTIONS (user 'postgres', password 'hrhk@123');
       
4. After that create new schema that will assigned all foreign objects. Then import object into this schema.

CREATE SCHEMA app;

IMPORT FOREIGN SCHEMA public
 FROM SERVER foreign_server
  INTO app;
 
  How to access foreign objects 

  SELECT * FROM app.grouptask;

or  
 
SELECT *   INTO grouptask FROM app.grouptask
select * from grouptask


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