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<title>Chapter21.Localization</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="chapter" lang="en" id="charset">
<div class="titlepage"><div><div><h2 class="title">
<a name="charset"></a>Chapter21.Localization</h2></div></div></div>
<div class="toc">
<p><b>Table of Contents</b></p>
<dl>
<dt><span class="sect1"><a href="charset.html#locale">21.1. Locale Support</a></span></dt>
<dd><dl>
<dt><span class="sect2"><a href="charset.html#id663047">21.1.1. Overview</a></span></dt>
<dt><span class="sect2"><a href="charset.html#id663399">21.1.2. Behavior</a></span></dt>
<dt><span class="sect2"><a href="charset.html#id663578">21.1.3. Problems</a></span></dt>
</dl></dd>
<dt><span class="sect1"><a href="multibyte.html">21.2. Character Set Support</a></span></dt>
<dd><dl>
<dt><span class="sect2"><a href="multibyte.html#multibyte-charset-supported">21.2.1. Supported Character Sets</a></span></dt>
<dt><span class="sect2"><a href="multibyte.html#id664688">21.2.2. Setting the Character Set</a></span></dt>
<dt><span class="sect2"><a href="multibyte.html#id664905">21.2.3. Automatic Character Set Conversion Between Server and Client</a></span></dt>
<dt><span class="sect2"><a href="multibyte.html#id666163">21.2.4. Further Reading</a></span></dt>
</dl></dd>
</dl>
</div>
<p> This chapter describes the available localization features from the
point of view of the administrator.
<span class="productname">PostgreSQL</span> supports localization with
two approaches:
</p>
<div class="itemizedlist"><ul type="disc">
<li><p> Using the locale features of the operating system to provide
locale-specific collation order, number formatting, translated
messages, and other aspects.
</p></li>
<li><p> Providing a number of different character sets defined in the
<span class="productname">PostgreSQL</span> server, including
multiple-byte character sets, to support storing text in all
kinds of languages, and providing character set translation between
client and server.
</p></li>
</ul></div>
<p>
</p>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="locale"></a>21.1.Locale Support</h2></div></div></div>
<a name="id663015"></a><p> <em class="firstterm">Locale</em> support refers to an application respecting
cultural preferences regarding alphabets, sorting, number
formatting, etc. <span class="productname">PostgreSQL</span> uses the standard ISO
C and <acronym class="acronym">POSIX</acronym> locale facilities provided by the server operating
system. For additional information refer to the documentation of your
system.
</p>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id663047"></a>21.1.1.Overview</h3></div></div></div>
<p> Locale support is automatically initialized when a database
cluster is created using <code class="command">initdb</code>.
<code class="command">initdb</code> will initialize the database cluster
with the locale setting of its execution environment by default,
so if your system is already set to use the locale that you want
in your database cluster then there is nothing else you need to
do. If you want to use a different locale (or you are not sure
which locale your system is set to), you can instruct
<code class="command">initdb</code> exactly which locale to use by
specifying the <code class="option">--locale</code> option. For example:
</p>
<pre class="screen">initdb --locale=sv_SE</pre>
<p>
</p>
<p> This example sets the locale to Swedish (<code class="literal">sv</code>) as spoken
in Sweden (<code class="literal">SE</code>). Other possibilities might be
<code class="literal">en_US</code> (U.S. English) and <code class="literal">fr_CA</code> (French
Canadian). If more than one character set can be useful for a
locale then the specifications look like this:
<code class="literal">cs_CZ.ISO8859-2</code>. What locales are available under what
names on your system depends on what was provided by the operating
system vendor and what was installed. (On most systems, the command
<code class="literal">locale -a</code> will provide a list of available locales.)
</p>
<p> Occasionally it is useful to mix rules from several locales, e.g.,
use English collation rules but Spanish messages. To support that, a
set of locale subcategories exist that control only a certain
aspect of the localization rules:
</p>
<div class="informaltable"><table border="1">
<colgroup>
<col>
<col>
</colgroup>
<tbody>
<tr>
<td><code class="envar">LC_COLLATE</code></td>
<td>String sort order</td>
</tr>
<tr>
<td><code class="envar">LC_CTYPE</code></td>
<td>Character classification (What is a letter? Its upper-case equivalent?)</td>
</tr>
<tr>
<td><code class="envar">LC_MESSAGES</code></td>
<td>Language of messages</td>
</tr>
<tr>
<td><code class="envar">LC_MONETARY</code></td>
<td>Formatting of currency amounts</td>
</tr>
<tr>
<td><code class="envar">LC_NUMERIC</code></td>
<td>Formatting of numbers</td>
</tr>
<tr>
<td><code class="envar">LC_TIME</code></td>
<td>Formatting of dates and times</td>
</tr>
</tbody>
</table></div>
<p>
The category names translate into names of
<code class="command">initdb</code> options to override the locale choice
for a specific category. For instance, to set the locale to
French Canadian, but use U.S. rules for formatting currency, use
<code class="literal">initdb --locale=fr_CA --lc-monetary=en_US</code>.
</p>
<p> If you want the system to behave as if it had no locale support,
use the special locale <code class="literal">C</code> or <code class="literal">POSIX</code>.
</p>
<p> The nature of some locale categories is that their value has to be
fixed for the lifetime of a database cluster. That is, once
<code class="command">initdb</code> has run, you cannot change them anymore.
<code class="literal">LC_COLLATE</code> and <code class="literal">LC_CTYPE</code> are
those categories. They affect the sort order of indexes, so they
must be kept fixed, or indexes on text columns will become corrupt.
<span class="productname">PostgreSQL</span> enforces this by recording
the values of <code class="envar">LC_COLLATE</code> and <code class="envar">LC_CTYPE</code> that are
seen by <code class="command">initdb</code>. The server automatically adopts
those two values when it is started.
</p>
<p> The other locale categories can be changed as desired whenever the
server is running by setting the run-time configuration variables
that have the same name as the locale categories (see <a href="runtime-config-client.html#runtime-config-client-format" title="17.10.2.Locale and Formatting">Section17.10.2, “Locale and Formatting”</a> for details). The defaults that are
chosen by <code class="command">initdb</code> are actually only written into
the configuration file <code class="filename">postgresql.conf</code> to
serve as defaults when the server is started. If you delete these
assignments from <code class="filename">postgresql.conf</code> then the
server will inherit the settings from its execution environment.
</p>
<p> Note that the locale behavior of the server is determined by the
environment variables seen by the server, not by the environment
of any client. Therefore, be careful to configure the correct locale settings
before starting the server. A consequence of this is that if
client and server are set up in different locales, messages may
appear in different languages depending on where they originated.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p> When we speak of inheriting the locale from the execution
environment, this means the following on most operating systems:
For a given locale category, say the collation, the following
environment variables are consulted in this order until one is
found to be set: <code class="envar">LC_ALL</code>, <code class="envar">LC_COLLATE</code>
(the variable corresponding to the respective category),
<code class="envar">LANG</code>. If none of these environment variables are
set then the locale defaults to <code class="literal">C</code>.
</p>
<p> Some message localization libraries also look at the environment
variable <code class="envar">LANGUAGE</code> which overrides all other locale
settings for the purpose of setting the language of messages. If
in doubt, please refer to the documentation of your operating
system, in particular the documentation about
<span class="application">gettext</span>, for more information.
</p>
</div>
<p> To enable messages to be translated to the user's preferred language,
<acronym class="acronym">NLS</acronym> must have been enabled at build time. This
choice is independent of the other locale support.
</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id663399"></a>21.1.2.Behavior</h3></div></div></div>
<p> The locale settings influence the following SQL features:
</p>
<div class="itemizedlist"><ul type="disc">
<li><p> Sort order in queries using <code class="literal">ORDER BY</code> on textual data
<a name="id663420"></a>
</p></li>
<li><p> The ability to use indexes with <code class="literal">LIKE</code> clauses
<a name="id663441"></a>
</p></li>
<li><p> The <code class="function">upper</code>, <code class="function">lower</code>, and <code class="function">initcap</code>
functions
<a name="id663476"></a>
<a name="id663486"></a>
</p></li>
<li><p> The <code class="function">to_char</code> family of functions
<a name="id663507"></a>
</p></li>
</ul></div>
<p>
</p>
<p> The drawback of using locales other than <code class="literal">C</code> or
<code class="literal">POSIX</code> in <span class="productname">PostgreSQL</span> is its performance
impact. It slows character handling and prevents ordinary indexes
from being used by <code class="literal">LIKE</code>. For this reason use locales
only if you actually need them.
</p>
<p> As a workaround to allow <span class="productname">PostgreSQL</span> to use indexes
with <code class="literal">LIKE</code> clauses under a non-C locale, several custom
operator classes exist. These allow the creation of an index that
performs a strict character-by-character comparison, ignoring
locale comparison rules. Refer to <a href="indexes-opclass.html" title="11.8.Operator Classes">Section11.8, “Operator Classes”</a>
for more information.
</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id663578"></a>21.1.3.Problems</h3></div></div></div>
<p> If locale support doesn't work in spite of the explanation above,
check that the locale support in your operating system is
correctly configured. To check what locales are installed on your
system, you may use the command <code class="literal">locale -a</code> if
your operating system provides it.
</p>
<p> Check that <span class="productname">PostgreSQL</span> is actually using the locale
that you think it is. <code class="envar">LC_COLLATE</code> and <code class="envar">LC_CTYPE</code>
settings are determined at <code class="command">initdb</code> time and cannot be
changed without repeating <code class="command">initdb</code>. Other locale
settings including <code class="envar">LC_MESSAGES</code> and <code class="envar">LC_MONETARY</code>
are initially determined by the environment the server is started
in, but can be changed on-the-fly. You can check the active locale
settings using the <code class="command">SHOW</code> command.
</p>
<p> The directory <code class="filename">src/test/locale</code> in the source
distribution contains a test suite for
<span class="productname">PostgreSQL</span>'s locale support.
</p>
<p> Client applications that handle server-side errors by parsing the
text of the error message will obviously have problems when the
server's messages are in a different language. Authors of such
applications are advised to make use of the error code scheme
instead.
</p>
<p> Maintaining catalogs of message translations requires the on-going
efforts of many volunteers that want to see
<span class="productname">PostgreSQL</span> speak their preferred language well.
If messages in your language are currently not available or not fully
translated, your assistance would be appreciated. If you want to
help, refer to <a href="nls.html" title="Chapter45.Native Language Support">Chapter45, <i>Native Language Support</i></a> or write to the developers'
mailing list.
</p>
</div>
</div>
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