postgres_fdw

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

The LightDB-A 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.

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

Installing and Registering the Module

The postgres_fdw module is installed when you install LightDB-A 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.

LightDB-A Database Limitations

When you use the foreign data wrapper to access LightDB-A 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 LightDB-A 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 LightDB-A Database table.

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

Additional Module Documentation

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