| Current File : //usr/share/doc/postgresql-9.2.24/html/file-fdw.html |
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>file_fdw</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REV="MADE"
HREF="mailto:pgsql-docs@postgresql.org"><LINK
REL="HOME"
TITLE="PostgreSQL 9.2.24 Documentation"
HREF="index.html"><LINK
REL="UP"
TITLE="Additional Supplied Modules"
HREF="contrib.html"><LINK
REL="PREVIOUS"
TITLE="earthdistance"
HREF="earthdistance.html"><LINK
REL="NEXT"
TITLE="fuzzystrmatch"
HREF="fuzzystrmatch.html"><LINK
REL="STYLESHEET"
TYPE="text/css"
HREF="stylesheet.css"><META
HTTP-EQUIV="Content-Type"
CONTENT="text/html; charset=ISO-8859-1"><META
NAME="creation"
CONTENT="2017-11-06T22:43:11"></HEAD
><BODY
CLASS="SECT1"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="5"
ALIGN="center"
VALIGN="bottom"
><A
HREF="index.html"
>PostgreSQL 9.2.24 Documentation</A
></TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
TITLE="earthdistance"
HREF="earthdistance.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
HREF="contrib.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="60%"
ALIGN="center"
VALIGN="bottom"
>Appendix F. Additional Supplied Modules</TD
><TD
WIDTH="20%"
ALIGN="right"
VALIGN="top"
><A
TITLE="fuzzystrmatch"
HREF="fuzzystrmatch.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="FILE-FDW"
>F.14. file_fdw</A
></H1
><P
> The <TT
CLASS="FILENAME"
>file_fdw</TT
> module provides the foreign-data wrapper
<CODE
CLASS="FUNCTION"
>file_fdw</CODE
>, which can be used to access data
files in the server's file system. Data files must be in a format
that can be read by <TT
CLASS="COMMAND"
>COPY FROM</TT
>;
see <A
HREF="sql-copy.html"
>COPY</A
> for details.
</P
><P
> A foreign table created using this wrapper can have the following options:
</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>filename</TT
></DT
><DD
><P
> Specifies the file to be read. Required. Must be an absolute path name.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>format</TT
></DT
><DD
><P
> Specifies the file's format,
the same as <TT
CLASS="COMMAND"
>COPY</TT
>'s <TT
CLASS="LITERAL"
>FORMAT</TT
> option.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>header</TT
></DT
><DD
><P
> Specifies whether the file has a header line,
the same as <TT
CLASS="COMMAND"
>COPY</TT
>'s <TT
CLASS="LITERAL"
>HEADER</TT
> option.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>delimiter</TT
></DT
><DD
><P
> Specifies the file's delimiter character,
the same as <TT
CLASS="COMMAND"
>COPY</TT
>'s <TT
CLASS="LITERAL"
>DELIMITER</TT
> option.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>quote</TT
></DT
><DD
><P
> Specifies the file's quote character,
the same as <TT
CLASS="COMMAND"
>COPY</TT
>'s <TT
CLASS="LITERAL"
>QUOTE</TT
> option.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>escape</TT
></DT
><DD
><P
> Specifies the file's escape character,
the same as <TT
CLASS="COMMAND"
>COPY</TT
>'s <TT
CLASS="LITERAL"
>ESCAPE</TT
> option.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>null</TT
></DT
><DD
><P
> Specifies the file's null string,
the same as <TT
CLASS="COMMAND"
>COPY</TT
>'s <TT
CLASS="LITERAL"
>NULL</TT
> option.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>encoding</TT
></DT
><DD
><P
> Specifies the file's encoding,
the same as <TT
CLASS="COMMAND"
>COPY</TT
>'s <TT
CLASS="LITERAL"
>ENCODING</TT
> option.
</P
></DD
></DL
></DIV
><P
> A column of a foreign table created using this wrapper can have the
following options:
</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>force_not_null</TT
></DT
><DD
><P
> This is a Boolean option. If true, it specifies that values of the
column should not be matched against the null string (that is, the
file-level <TT
CLASS="LITERAL"
>null</TT
> option). This has the same effect
as listing the column in <TT
CLASS="COMMAND"
>COPY</TT
>'s
<TT
CLASS="LITERAL"
>FORCE_NOT_NULL</TT
> option.
</P
></DD
></DL
></DIV
><P
> <TT
CLASS="COMMAND"
>COPY</TT
>'s <TT
CLASS="LITERAL"
>OIDS</TT
> and
<TT
CLASS="LITERAL"
>FORCE_QUOTE</TT
> options are currently not supported by
<TT
CLASS="LITERAL"
>file_fdw</TT
>.
</P
><P
> These options can only be specified for a foreign table or its columns, not
in the options of the <TT
CLASS="LITERAL"
>file_fdw</TT
> foreign-data wrapper, nor in the
options of a server or user mapping using the wrapper.
</P
><P
> 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.
</P
><P
> For a foreign table using <TT
CLASS="LITERAL"
>file_fdw</TT
>, <TT
CLASS="COMMAND"
>EXPLAIN</TT
> shows
the name of the file to be read. Unless <TT
CLASS="LITERAL"
>COSTS OFF</TT
> is
specified, the file size (in bytes) is shown as well.
</P
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN148264"
></A
><P
><B
>Example F-1. Create a Foreign Table for PostgreSQL CSV Logs</B
></P
><P
> One of the obvious uses for the <TT
CLASS="LITERAL"
>file_fdw</TT
> is to make
the PostgreSQL activity log available as a table for querying. To
do this, first you must be logging to a CSV file, which here we
will call <TT
CLASS="LITERAL"
>pglog.csv</TT
>. First, install <TT
CLASS="LITERAL"
>file_fdw</TT
>
as an extension:
</P
><PRE
CLASS="PROGRAMLISTING"
>CREATE EXTENSION file_fdw;</PRE
><P
> Then create a foreign server:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE SERVER pglog FOREIGN DATA WRAPPER file_fdw;</PRE
><P>
</P
><P
> Now you are ready to create the foreign data table. Using the
<TT
CLASS="COMMAND"
>CREATE FOREIGN TABLE</TT
> command, you will need to define
the columns for the table, the CSV file name, and its format:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE FOREIGN TABLE pglog (
log_time timestamp(3) with time zone,
user_name text,
database_name text,
process_id integer,
connection_from text,
session_id text,
session_line_num bigint,
command_tag text,
session_start_time timestamp with time zone,
virtual_transaction_id text,
transaction_id bigint,
error_severity text,
sql_state_code text,
message text,
detail text,
hint text,
internal_query text,
internal_query_pos integer,
context text,
query text,
query_pos integer,
location text,
application_name text
) SERVER pglog
OPTIONS ( filename '/home/josh/9.1/data/pg_log/pglog.csv', format 'csv' );</PRE
><P>
</P
><P
> That's it — now you can query your log directly. In production, of course,
you would need to define some way to adjust to log rotation.
</P
></DIV
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="earthdistance.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="fuzzystrmatch.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>earthdistance</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="contrib.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>fuzzystrmatch</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>