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))