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Documentation of the system catalogs, directed toward PostgreSQL developers

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<chapter id="catalogs">

<entry>check constraints, unique / primary key constraints, foreign key constraints</entry>

</row>

<row>

<entry>pg_conversion</entry>

<entry>encoding conversion information</entry>

</row>

<row>

<entry>pg_database</entry>

<entry>databases within this database cluster</entry>

</sect1>

<sect1 id="catalog-pg-conversion">

<title>pg_conversion</title>

<para>

This system catalog stores encoding conversion information. See

<command>CREATE CONVERSION</command> for more information.

</para>

<table>

<title>pg_conversion Columns</title>

<tgroup cols=4>

<thead>

<row>

<entry>Name</entry>

<entry>Type</entry>

<entry>References</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry>conname</entry>

<entry><type>name</type></entry>

<entry></entry>

<entry>Conversion name (unique within a namespace)</entry>

</row>

<row>

<entry>connamespace</entry>

<entry><type>oid</type></entry>

<entry>pg_namespace.oid</entry>

<entry>

The OID of the namespace that contains this conversion

</entry>

</row>

<row>

<entry>conowner</entry>

<entry><type>int4</type></entry>

<entry>pg_shadow.usesysid</entry>

<entry>Owner (creator) of the namespace</entry>

</row>

<row>

<entry>conforencoding</entry>

<entry><type>int4</type></entry>

<entry></entry>

<entry>Source(for) encoding ID</entry>

</row>

<row>

<entry>contoencoding</entry>

<entry><type>int4</type></entry>

<entry></entry>

<entry>Destination(to) encoding ID</entry>

</row>

<row>

<entry>conproc</entry>

<entry><type>regproc</type></entry>

<entry>pg_proc.oid</entry>

<entry>Conversion procedure</entry>

</row>

<row>

<entry>condefault</entry>

<entry><type>boolean</type></entry>

<entry></entry>

<entry>true if this is the default conversion</entry>

</row>

</tbody>

</tgroup>

</table>

</sect1>

<sect1 id="catalog-pg-database">

<title>pg_database</title>

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<chapter id="charset">

<title>Localization</>

<para>

Tatsuo Ishii (<email>ishii@postgresql.org</email>),

last updated2000-03-22.

last updated2002-07-24.

Check <ulink

url="http://www.sra.co.jp/people/t-ishii/PostgreSQL/">Tatsuo's

web site</ulink> for more information.

overridden when you create a database using

<application>createdb</application> or by using the SQL command

<command>CREATE DATABASE</>. So you can have multiple databases each with

a different encoding system.

a different encoding system. Note that <acronym>MB</acronym> can

handle single byte characters sets such as ISO-8859-1.

</para>

<sect2>

<title>Enabling Multibyte Support</title>

<para>

Run configure with the multibyte option:

Multibyte support is enabled by default since PostgreSQL version 7.3.

</para>

<synopsis>

./configure --enable-multibyte<optional>=<replaceable>encoding_system</replaceable></optional>

</synopsis>

<sect2>

<title>Supported character set encodings</title>

<table tocentry="1">

<title>Character Set Encodings</title>

<literal>LATIN8</>, and <literal>LATIN10</>.

</para>

</important>

</sect2>

<para>

Here is an example of configuring

<productname>PostgreSQL</productname> to use a Japanese encoding by

default:

<screen>

$ <userinput>./configure --enable-multibyte=EUC_JP</userinput>

</screen>

</para>

<para>

If the encoding system is omitted (<literal>./configure --enable-multibyte</literal>),

<literal>SQL_ASCII</> is assumed.

</para>

</sect2>

<sect2>

<title>Setting the Encoding</title>

sets the default encoding to <literal>EUC_JP</literal> (Extended Unix Code for Japanese).

Note that you can use <option>--encoding</option> instead of <option>-E</option> if you prefer

to type longer option strings.

If no <option>-E</> or <option>--encoding</option> option is given, the encoding

specified at configure time is used.

If no <option>-E</> or <option>--encoding</option> option is

given, SQL_ASCII is used.

</para>

<para>

</sect2>

<sect2>

<title>Automatic encodingtranslation between server and

<title>Automatic encodingconversion between server and

client</title>

<para>

<productname>PostgreSQL</productname> supports an automatic

encoding translation between server

and client for some encodings. The available combinations are

listed in <xref linkend="multibyte-translation-table">.

encoding conversion between server and client for some

encodings. The conversion info is stored in pg_converson system

catalog. You can create a new conversion by using <command>CREATE

CONVERSION</command>. PostgreSQL comes with some predefined

conversions. They are listed in <xref

linkend="multibyte-translation-table">.

</para>

<table tocentry="1" id="multibyte-translation-table">

be overridden using any of the other methods mentioned above.)

</para>

</listitem>

<listitem>

<para>

Using client_encoding variable.

If client_encoding variable in postgresql.conf is set, that

client encoding is automatically selected when a connection to the

server is made. (This can subsequently be overridden using any of the

other methods mentioned above.)

</para>

</listitem>

</itemizedlist>

</para>

</sect2>

The Unicode conversion functionality is automatically enabled

if <option>--enable-multibyte</option> is specified.

</para>

<para>

For 7.3, <option>--enable-unicode-conversion</option> nor

<option>--enable-multibyte</option> is needed.

</para>

</sect2>

<sect2>