Chapter 58. Writing a Foreign Data Wrapper

   Table of Contents

   58.1. Foreign Data Wrapper Functions
   58.2. Foreign Data Wrapper Callback Routines

        58.2.1. FDW Routines for Scanning Foreign Tables
        58.2.2. FDW Routines for Scanning Foreign Joins
        58.2.3. FDW Routines for Planning Post-Scan/Join Processing
        58.2.4. FDW Routines for Updating Foreign Tables
        58.2.5. FDW Routines for TRUNCATE
        58.2.6. FDW Routines for Row Locking
        58.2.7. FDW Routines for EXPLAIN
        58.2.8. FDW Routines for ANALYZE
        58.2.9. FDW Routines for IMPORT FOREIGN SCHEMA
        58.2.10. FDW Routines for Parallel Execution
        58.2.11. FDW Routines for Asynchronous Execution
        58.2.12. FDW Routines for Reparameterization of Paths

   58.3. Foreign Data Wrapper Helper Functions
   58.4. Foreign Data Wrapper Query Planning
   58.5. Row Locking in Foreign Data Wrappers

   All operations on a foreign table are handled through its foreign data
   wrapper, which consists of a set of functions that the core server
   calls. The foreign data wrapper is responsible for fetching data from
   the remote data source and returning it to the PostgreSQL executor. If
   updating foreign tables is to be supported, the wrapper must handle
   that, too. This chapter outlines how to write a new foreign data
   wrapper.

   The foreign data wrappers included in the standard distribution are
   good references when trying to write your own. Look into the contrib
   subdirectory of the source tree. The CREATE FOREIGN DATA WRAPPER
   reference page also has some useful details.

Note

   The SQL standard specifies an interface for writing foreign data
   wrappers. However, PostgreSQL does not implement that API, because the
   effort to accommodate it into PostgreSQL would be large, and the
   standard API hasn't gained wide adoption anyway.