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<!-- doc/src/sgml/file-fdw.sgml -->
<sect1 id="file-fdw">
<title>file_fdw</title>
<indexterm zone="file-fdw">
<primary>file_fdw</primary>
</indexterm>
<para>
The <filename>file_fdw</> module provides the foreign-data wrapper
<function>file_fdw</function>, which can be used to access data
files in the server's filesystem. Data files must be in a format
that can be read by <command>COPY FROM</command>;
see <xref linkend="sql-copy"> for details.
</para>
<para>
A foreign table created using this wrapper can have the following options:
</para>
<variablelist>
<varlistentry>
<term><literal>filename</literal></term>
<listitem>
<para>
Specifies the file to be read. Required. Must be an absolute path name.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>format</literal></term>
<listitem>
<para>
Specifies the file's format,
the same as <command>COPY</>'s <literal>FORMAT</literal> option.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>header</literal></term>
<listitem>
<para>
Specifies whether the file has a header line,
the same as <command>COPY</>'s <literal>HEADER</literal> option.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>delimiter</literal></term>
<listitem>
<para>
Specifies the file's delimiter character,
the same as <command>COPY</>'s <literal>DELIMITER</literal> option.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>quote</literal></term>
<listitem>
<para>
Specifies the file's quote character,
the same as <command>COPY</>'s <literal>QUOTE</literal> option.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>escape</literal></term>
<listitem>
<para>
Specifies the file's escape character,
the same as <command>COPY</>'s <literal>ESCAPE</literal> option.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>null</literal></term>
<listitem>
<para>
Specifies the file's null string,
the same as <command>COPY</>'s <literal>NULL</literal> option.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
<command>COPY</>'s <literal>OIDS</literal>, <literal>FORCE_QUOTE</literal>,
and <literal>FORCE_NOT_NULL</literal> options are currently not supported by
<literal>file_fdw</>.
</para>
<para>
These options can only be specified for a foreign table, not in the
options of the <literal>file_fdw</> foreign-data wrapper, nor in the
options of a server or user mapping using the wrapper.
</para>
<para>
Changing table-level options requires superuser privileges, for security
reasons: only a superuser should be able to determine which file is read.
In principle non-superusers could be allowed to change the other options,
but that's not supported at present.
</para>
<para>
For a foreign table using <literal>file_fdw</>, <command>EXPLAIN</> shows
the name of the file to be read. Unless <literal>COSTS OFF</> is
specified, the file size (in bytes) is shown as well.
</para>
</sect1>
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