NAME

       CREATE_FOREIGN_DATA_WRAPPER - define a new foreign-data wrapper

SYNOPSIS

       CREATE FOREIGN DATA WRAPPER name
           [ HANDLER handler_function | NO HANDLER ]
           [ VALIDATOR validator_function | NO VALIDATOR ]
           [ OPTIONS ( option 'value' [, ... ] ) ]

DESCRIPTION

       CREATE FOREIGN DATA WRAPPER creates a new foreign-data wrapper. The user who defines a foreign-data
       wrapper becomes its owner.

       The foreign-data wrapper name must be unique within the database.

       Only superusers can create foreign-data wrappers.

PARAMETERS

       name
           The name of the foreign-data wrapper to be created.

       HANDLER handler_function
           handler_function is the name of a previously registered function that will be called to retrieve the
           execution functions for foreign tables. The handler function must take no arguments, and its return
           type must be fdw_handler.

           It is possible to create a foreign-data wrapper with no handler function, but foreign tables using
           such a wrapper can only be declared, not accessed.

       VALIDATOR validator_function
           validator_function is the name of a previously registered function that will be called to check the
           generic options given to the foreign-data wrapper, as well as options for foreign servers, user
           mappings and foreign tables using the foreign-data wrapper. If no validator function or NO VALIDATOR
           is specified, then options will not be checked at creation time. (Foreign-data wrappers will possibly
           ignore or reject invalid option specifications at run time, depending on the implementation.) The
           validator function must take two arguments: one of type text[], which will contain the array of
           options as stored in the system catalogs, and one of type oid, which will be the OID of the system
           catalog containing the options. The return type is ignored; the function should report invalid
           options using the ereport(ERROR) function.

       OPTIONS ( option 'value' [, ... ] )
           This clause specifies options for the new foreign-data wrapper. The allowed option names and values
           are specific to each foreign data wrapper and are validated using the foreign-data wrapper's
           validator function. Option names must be unique.

NOTES

       PostgreSQL's foreign-data functionality is still under active development. Optimization of queries is
       primitive (and mostly left to the wrapper, too). Thus, there is considerable room for future performance
       improvements.

EXAMPLES

       Create a useless foreign-data wrapper dummy:

           CREATE FOREIGN DATA WRAPPER dummy;

       Create a foreign-data wrapper file with handler function file_fdw_handler:

           CREATE FOREIGN DATA WRAPPER file HANDLER file_fdw_handler;

       Create a foreign-data wrapper mywrapper with some options:

           CREATE FOREIGN DATA WRAPPER mywrapper
               OPTIONS (debug 'true');

COMPATIBILITY

       CREATE FOREIGN DATA WRAPPER conforms to ISO/IEC 9075-9 (SQL/MED), with the exception that the HANDLER and
       VALIDATOR clauses are extensions and the standard clauses LIBRARY and LANGUAGE are not implemented in
       PostgreSQL.

       Note, however, that the SQL/MED functionality as a whole is not yet conforming.

SEE ALSO

       ALTER FOREIGN DATA WRAPPER (ALTER_FOREIGN_DATA_WRAPPER(7)), DROP FOREIGN DATA WRAPPER
       (DROP_FOREIGN_DATA_WRAPPER(7)), CREATE SERVER (CREATE_SERVER(7)), CREATE USER MAPPING
       (CREATE_USER_MAPPING(7)), CREATE FOREIGN TABLE (CREATE_FOREIGN_TABLE(7))