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><H1
><A
NAME="SQL-CREATEFOREIGNDATAWRAPPER"
></A
>CREATE FOREIGN DATA WRAPPER</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN56787"
></A
><H2
>Name</H2
>CREATE FOREIGN DATA WRAPPER -- define a new foreign-data wrapper</DIV
><A
NAME="AEN56790"
></A
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN56792"
></A
><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
>CREATE FOREIGN DATA WRAPPER <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>
[ VALIDATOR <TT
CLASS="REPLACEABLE"
><I
>valfunction</I
></TT
> | NO VALIDATOR ]
[ OPTIONS ( <TT
CLASS="REPLACEABLE"
><I
>option</I
></TT
> '<TT
CLASS="REPLACEABLE"
><I
>value</I
></TT
>' [, ... ] ) ]</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN56798"
></A
><H2
>Description</H2
><P
> <TT
CLASS="COMMAND"
>CREATE FOREIGN DATA WRAPPER</TT
> creates a new
foreign-data wrapper. The user who defines a foreign-data wrapper
becomes its owner.
</P
><P
> The foreign-data wrapper name must be unique within the database.
</P
><P
> Only superusers can create foreign-data wrappers.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN56804"
></A
><H2
>Parameters</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
></DT
><DD
><P
> The name of the foreign-data wrapper to be created.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>VALIDATOR <TT
CLASS="REPLACEABLE"
><I
>valfunction</I
></TT
></TT
></DT
><DD
><P
> <TT
CLASS="REPLACEABLE"
><I
>valfunction</I
></TT
> 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 <TT
CLASS="LITERAL"
>NO
VALIDATOR</TT
> 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 <TT
CLASS="TYPE"
>text[]</TT
>, which will
contain the array of options as stored in the system catalogs,
and one of type <TT
CLASS="TYPE"
>oid</TT
>, 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
<CODE
CLASS="FUNCTION"
>ereport()</CODE
> function.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>OPTIONS ( <TT
CLASS="REPLACEABLE"
><I
>option</I
></TT
> '<TT
CLASS="REPLACEABLE"
><I
>value</I
></TT
>' [, ... ] )</TT
></DT
><DD
><P
> 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.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN56830"
></A
><H2
>Notes</H2
><P
> 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 <SPAN
CLASS="APPLICATION"
>dblink</SPAN
>;
see <A
HREF="dblink.html"
>Section F.8</A
>. The functionality to actually query
external data through a foreign-data wrapper library does not exist
yet.
</P
><P
> There is currently one foreign-data wrapper validator function
provided:
<TT
CLASS="FILENAME"
>postgresql_fdw_validator</TT
>, which accepts
options corresponding to <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> connection
parameters.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN56838"
></A
><H2
>Examples</H2
><P
> Create a foreign-data wrapper <TT
CLASS="LITERAL"
>dummy</TT
>:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE FOREIGN DATA WRAPPER dummy;</PRE
><P>
</P
><P
> Create a foreign-data wrapper <TT
CLASS="LITERAL"
>postgresql</TT
> with
validator function <TT
CLASS="LITERAL"
>postgresql_fdw_validator</TT
>:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE FOREIGN DATA WRAPPER postgresql VALIDATOR postgresql_fdw_validator;</PRE
><P>
</P
><P
> Create a foreign-data wrapper <TT
CLASS="LITERAL"
>mywrapper</TT
> with some
options:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE FOREIGN DATA WRAPPER mywrapper
OPTIONS (debug 'true');</PRE
><P>
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN56850"
></A
><H2
>Compatibility</H2
><P
> <TT
CLASS="COMMAND"
>CREATE FOREIGN DATA WRAPPER</TT
> conforms to ISO/IEC
9075-9 (SQL/MED), with the exception that
the <TT
CLASS="LITERAL"
>VALIDATOR</TT
> clause is an extension and the
clauses <TT
CLASS="LITERAL"
>LIBRARY</TT
> and <TT
CLASS="LITERAL"
>LANGUAGE</TT
>
are not yet implemented in PostgreSQL.
</P
><P
> Note, however, that the SQL/MED functionality as a whole is not yet
conforming.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN56858"
></A
><H2
>See Also</H2
><A
HREF="sql-alterforeigndatawrapper.html"
><I
>ALTER FOREIGN DATA WRAPPER</I
></A
>, <A
HREF="sql-dropforeigndatawrapper.html"
><I
>DROP FOREIGN DATA WRAPPER</I
></A
>, <A
HREF="sql-createserver.html"
><I
>CREATE SERVER</I
></A
>, <A
HREF="sql-createusermapping.html"
><I
>CREATE USER MAPPING</I
></A
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