The postgres_fdw module is a foreign data wrapper (FDW) that you can use to access data stored in a remote PostgreSQL or Greenplum database.

The Greenplum Database postgres_fdw module is a modified version of the PostgreSQL postgres_fdw module. The module behaves as described in the PostgreSQL postgres_fdw documentation when you use it to access a remote PostgreSQL database.


There are some restrictions and limitations when you use this foreign data wrapper module to access Greenplum Database, described below.

Installing and Registering the Module

The postgres_fdw module is installed when you install Greenplum Database. Before you can use the foreign data wrapper, you must register the postgres_fdw extension in each database in which you want to use the foreign data wrapper. Refer to Installing Additional Supplied Modules for more information.

Greenplum Database Limitations

When you use the foreign data wrapper to access Greenplum Database, postgres_fdw has the following limitations:

  • The ctid is not guaranteed to uniquely identify the physical location of a row within its table. For example, the following statements may return incorrect results when the foreign table references a Greenplum Database table:

    INSERT INTO rem1(f2) VALUES ('test') RETURNING ctid;
    SELECT * FROM ft1, t1 WHERE t1.ctid = '(0,2)'; 
  • postgres_fdw does not support local or remote triggers when you use it to access a foreign table that references a Greenplum Database table.

  • UPDATE or DELETE operations on a foreign table that references a Greenplum table are not guaranteed to work correctly.

Additional Module Documentation

Refer to the postgres_fdw PostgreSQL documentation for detailed information about this module.

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