manuals

NAME

       CREATE_FOREIGN_DATA_WRAPPER - define a new foreign-data wrapper

SYNOPSIS

       CREATE FOREIGN DATA WRAPPER name
           [ VALIDATOR valfunction | 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.

       VALIDATOR valfunction
           valfunction 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 to foreign servers and user
           mappings 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 indicate invalid options using
           the ereport() 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 library.
           Option names must be unique.

NOTES

       At the moment, the foreign-data wrapper functionality is very
       rudimentary. The purpose of foreign-data wrappers, foreign servers, and
       user mappings is to store this information in a standard way so that it
       can be queried by interested applications. One such application is
       dblink; see Section F.8, “dblink”, in the documentation. The
       functionality to actually query external data through a foreign-data
       wrapper library does not exist yet.

       There is currently one foreign-data wrapper validator function
       provided: postgresql_fdw_validator, which accepts options corresponding
       to libpq connection parameters.

EXAMPLES

       Create a foreign-data wrapper dummy:

           CREATE FOREIGN DATA WRAPPER dummy;

       Create a foreign-data wrapper postgresql with validator function
       postgresql_fdw_validator:

           CREATE FOREIGN DATA WRAPPER postgresql VALIDATOR postgresql_fdw_validator;

       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 VALIDATOR clause is an extension and the clauses
       LIBRARY and LANGUAGE are not yet 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))