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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>24.1. Locale Support</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="charset.html" title="Chapter 24. Localization" /><link rel="next" href="collation.html" title="24.2. Collation Support" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">24.1. Locale Support</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="charset.html" title="Chapter 24. Localization">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="charset.html" title="Chapter 24. Localization">Up</a></td><th width="60%" align="center">Chapter 24. Localization</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="collation.html" title="24.2. Collation Support">Next</a></td></tr></table><hr /></div><div class="sect1" id="LOCALE"><div class="titlepage"><div><div><h2 class="title" style="clear: both">24.1. Locale Support <a href="#LOCALE" class="id_link">#</a></h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="locale.html#LOCALE-OVERVIEW">24.1.1. Overview</a></span></dt><dt><span class="sect2"><a href="locale.html#LOCALE-BEHAVIOR">24.1.2. Behavior</a></span></dt><dt><span class="sect2"><a href="locale.html#LOCALE-SELECTING-LOCALES">24.1.3. Selecting Locales</a></span></dt><dt><span class="sect2"><a href="locale.html#LOCALE-PROVIDERS">24.1.4. Locale Providers</a></span></dt><dt><span class="sect2"><a href="locale.html#ICU-LOCALES">24.1.5. ICU Locales</a></span></dt><dt><span class="sect2"><a href="locale.html#LOCALE-PROBLEMS">24.1.6. Problems</a></span></dt></dl></div><a id="id-1.6.11.3.2" class="indexterm"></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" id="LOCALE-OVERVIEW"><div class="titlepage"><div><div><h3 class="title">24.1.1. Overview <a href="#LOCALE-OVERVIEW" class="id_link">#</a></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 for Unix systems sets the locale to Swedish
(<code class="literal">sv</code>) as spoken
in Sweden (<code class="literal">SE</code>). Other possibilities might include
<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 used for a
locale then the specifications can take the form
<em class="replaceable"><code>language_territory.codeset</code></em>. For example,
<code class="literal">fr_BE.UTF-8</code> represents the French language (fr) as
spoken in Belgium (BE), with a <acronym class="acronym">UTF-8</acronym> character set
encoding.
</p><p>
What locales are available on your
system under what names depends on what was provided by the operating
system vendor and what was installed. On most Unix systems, the command
<code class="literal">locale -a</code> will provide a list of available locales.
Windows uses more verbose locale names, such as <code class="literal">German_Germany</code>
or <code class="literal">Swedish_Sweden.1252</code>, but the principles are the same.
</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 certain
aspects of the localization rules:
</p><div class="informaltable"><table class="informaltable" border="1"><colgroup><col class="col1" /><col class="col2" /></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 name <code class="literal">C</code>, or equivalently
<code class="literal">POSIX</code>.
</p><p>
Some locale categories must have their values
fixed when the database is created. You can use different settings
for different databases, but once a database is created, you cannot
change them for that database anymore. <code class="literal">LC_COLLATE</code>
and <code class="literal">LC_CTYPE</code> are these categories. They affect
the sort order of indexes, so they must be kept fixed, or indexes on
text columns would become corrupt.
(But you can alleviate this restriction using collations, as discussed
in <a class="xref" href="collation.html" title="24.2. Collation Support">Section 24.2</a>.)
The default values for these
categories are determined when <code class="command">initdb</code> is run, and
those values are used when new databases are created, unless
specified otherwise in the <code class="command">CREATE DATABASE</code> command.
</p><p>
The other locale categories can be changed whenever desired
by setting the server configuration parameters
that have the same name as the locale categories (see <a class="xref" href="runtime-config-client.html#RUNTIME-CONFIG-CLIENT-FORMAT" title="20.11.2. Locale and Formatting">Section 20.11.2</a> for details). The values
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 remove 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 might
appear in different languages depending on where they originated.
</p><div class="note"><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>
(or 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>.
</p></div><p>
To enable messages to be translated to the user's preferred language,
<acronym class="acronym">NLS</acronym> must have been selected at build time
(<code class="literal">configure --enable-nls</code>). All other locale support is
built in automatically.
</p></div><div class="sect2" id="LOCALE-BEHAVIOR"><div class="titlepage"><div><div><h3 class="title">24.1.2. Behavior <a href="#LOCALE-BEHAVIOR" class="id_link">#</a></h3></div></div></div><p>
The locale settings influence the following SQL features:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
Sort order in queries using <code class="literal">ORDER BY</code> or the standard
comparison operators on textual data
<a id="id-1.6.11.3.5.2.1.1.1.2" class="indexterm"></a>
</p></li><li class="listitem"><p>
The <code class="function">upper</code>, <code class="function">lower</code>, and <code class="function">initcap</code>
functions
<a id="id-1.6.11.3.5.2.1.2.1.4" class="indexterm"></a>
<a id="id-1.6.11.3.5.2.1.2.1.5" class="indexterm"></a>
</p></li><li class="listitem"><p>
Pattern matching operators (<code class="literal">LIKE</code>, <code class="literal">SIMILAR TO</code>,
and POSIX-style regular expressions); locales affect both case
insensitive matching and the classification of characters by
character-class regular expressions
<a id="id-1.6.11.3.5.2.1.3.1.3" class="indexterm"></a>
<a id="id-1.6.11.3.5.2.1.3.1.4" class="indexterm"></a>
</p></li><li class="listitem"><p>
The <code class="function">to_char</code> family of functions
<a id="id-1.6.11.3.5.2.1.4.1.2" class="indexterm"></a>
</p></li><li class="listitem"><p>
The ability to use indexes with <code class="literal">LIKE</code> clauses
</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 class="xref" href="indexes-opclass.html" title="11.10. Operator Classes and Operator Families">Section 11.10</a>
for more information. Another approach is to create indexes using
the <code class="literal">C</code> collation, as discussed in
<a class="xref" href="collation.html" title="24.2. Collation Support">Section 24.2</a>.
</p></div><div class="sect2" id="LOCALE-SELECTING-LOCALES"><div class="titlepage"><div><div><h3 class="title">24.1.3. Selecting Locales <a href="#LOCALE-SELECTING-LOCALES" class="id_link">#</a></h3></div></div></div><p>
Locales can be selected in different scopes depending on requirements.
The above overview showed how locales are specified using
<code class="command">initdb</code> to set the defaults for the entire cluster. The
following list shows where locales can be selected. Each item provides
the defaults for the subsequent items, and each lower item allows
overriding the defaults on a finer granularity.
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
As explained above, the environment of the operating system provides the
defaults for the locales of a newly initialized database cluster. In
many cases, this is enough: If the operating system is configured for
the desired language/territory, then
<span class="productname">PostgreSQL</span> will by default also behave
according to that locale.
</p></li><li class="listitem"><p>
As shown above, command-line options for <code class="command">initdb</code>
specify the locale settings for a newly initialized database cluster.
Use this if the operating system does not have the locale configuration
you want for your database system.
</p></li><li class="listitem"><p>
A locale can be selected separately for each database. The SQL command
<code class="command">CREATE DATABASE</code> and its command-line equivalent
<code class="command">createdb</code> have options for that. Use this for example
if a database cluster houses databases for multiple tenants with
different requirements.
</p></li><li class="listitem"><p>
Locale settings can be made for individual table columns. This uses an
SQL object called <em class="firstterm">collation</em> and is explained in
<a class="xref" href="collation.html" title="24.2. Collation Support">Section 24.2</a>. Use this for example to sort data in
different languages or customize the sort order of a particular table.
</p></li><li class="listitem"><p>
Finally, locales can be selected for an individual query. Again, this
uses SQL collation objects. This could be used to change the sort order
based on run-time choices or for ad-hoc experimentation.
</p></li></ol></div></div><div class="sect2" id="LOCALE-PROVIDERS"><div class="titlepage"><div><div><h3 class="title">24.1.4. Locale Providers <a href="#LOCALE-PROVIDERS" class="id_link">#</a></h3></div></div></div><p>
<span class="productname">PostgreSQL</span> supports multiple <em class="firstterm">locale
providers</em>. This specifies which library supplies the locale
data. One standard provider name is <code class="literal">libc</code>, which uses
the locales provided by the operating system C library. These are the
locales used by most tools provided by the operating system. Another
provider is <code class="literal">icu</code>, which uses the external
ICU<a id="id-1.6.11.3.7.2.5" class="indexterm"></a> library. ICU locales can
only be used if support for ICU was configured when PostgreSQL was built.
</p><p>
The commands and tools that select the locale settings, as described
above, each have an option to select the locale provider. The examples
shown earlier all use the <code class="literal">libc</code> provider, which is the
default. Here is an example to initialize a database cluster using the
ICU provider:
</p><pre class="programlisting">
initdb --locale-provider=icu --icu-locale=en
</pre><p>
See the description of the respective commands and programs for
details. Note that you can mix locale providers at different
granularities, for example use <code class="literal">libc</code> by default for the
cluster but have one database that uses the <code class="literal">icu</code>
provider, and then have collation objects using either provider within
those databases.
</p><p>
Which locale provider to use depends on individual requirements. For most
basic uses, either provider will give adequate results. For the libc
provider, it depends on what the operating system offers; some operating
systems are better than others. For advanced uses, ICU offers more locale
variants and customization options.
</p></div><div class="sect2" id="ICU-LOCALES"><div class="titlepage"><div><div><h3 class="title">24.1.5. ICU Locales <a href="#ICU-LOCALES" class="id_link">#</a></h3></div></div></div><div class="sect3" id="ICU-LOCALE-NAMES"><div class="titlepage"><div><div><h4 class="title">24.1.5.1. ICU Locale Names <a href="#ICU-LOCALE-NAMES" class="id_link">#</a></h4></div></div></div><p>
The ICU format for the locale name is a <a class="link" href="locale.html#ICU-LANGUAGE-TAG" title="24.1.5.3. Language Tag">Language Tag</a>.
</p><pre class="programlisting">
CREATE COLLATION mycollation1 (provider = icu, locale = 'ja-JP');
CREATE COLLATION mycollation2 (provider = icu, locale = 'fr');
</pre><p>
</p></div><div class="sect3" id="ICU-CANONICALIZATION"><div class="titlepage"><div><div><h4 class="title">24.1.5.2. Locale Canonicalization and Validation <a href="#ICU-CANONICALIZATION" class="id_link">#</a></h4></div></div></div><p>
When defining a new ICU collation object or database with ICU as the
provider, the given locale name is transformed ("canonicalized") into a
language tag if not already in that form. For instance,
</p><pre class="screen">
CREATE COLLATION mycollation3 (provider = icu, locale = 'en-US-u-kn-true');
NOTICE: using standard form "en-US-u-kn" for locale "en-US-u-kn-true"
CREATE COLLATION mycollation4 (provider = icu, locale = 'de_DE.utf8');
NOTICE: using standard form "de-DE" for locale "de_DE.utf8"
</pre><p>
If you see this notice, ensure that the <code class="symbol">provider</code> and
<code class="symbol">locale</code> are the expected result. For consistent results
when using the ICU provider, specify the canonical <a class="link" href="locale.html#ICU-LANGUAGE-TAG" title="24.1.5.3. Language Tag">language tag</a> instead of relying on the
transformation.
</p><p>
A locale with no language name, or the special language name
<code class="literal">root</code>, is transformed to have the language
<code class="literal">und</code> ("undefined").
</p><p>
ICU can transform most libc locale names, as well as some other formats,
into language tags for easier transition to ICU. If a libc locale name is
used in ICU, it may not have precisely the same behavior as in libc.
</p><p>
If there is a problem interpreting the locale name, or if the locale name
represents a language or region that ICU does not recognize, you will see
the following warning:
</p><pre class="screen">
CREATE COLLATION nonsense (provider = icu, locale = 'nonsense');
WARNING: ICU locale "nonsense" has unknown language "nonsense"
HINT: To disable ICU locale validation, set parameter icu_validation_level to DISABLED.
CREATE COLLATION
</pre><p>
<a class="xref" href="runtime-config-client.html#GUC-ICU-VALIDATION-LEVEL">icu_validation_level</a> controls how the message is
reported. Unless set to <code class="literal">ERROR</code>, the collation will
still be created, but the behavior may not be what the user intended.
</p></div><div class="sect3" id="ICU-LANGUAGE-TAG"><div class="titlepage"><div><div><h4 class="title">24.1.5.3. Language Tag <a href="#ICU-LANGUAGE-TAG" class="id_link">#</a></h4></div></div></div><p>
A language tag, defined in BCP 47, is a standardized identifier used to
identify languages, regions, and other information about a locale.
</p><p>
Basic language tags are simply
<em class="replaceable"><code>language</code></em><code class="literal">-</code><em class="replaceable"><code>region</code></em>;
or even just <em class="replaceable"><code>language</code></em>. The
<em class="replaceable"><code>language</code></em> is a language code
(e.g. <code class="literal">fr</code> for French), and
<em class="replaceable"><code>region</code></em> is a region code
(e.g. <code class="literal">CA</code> for Canada). Examples:
<code class="literal">ja-JP</code>, <code class="literal">de</code>, or
<code class="literal">fr-CA</code>.
</p><p>
Collation settings may be included in the language tag to customize
collation behavior. ICU allows extensive customization, such as
sensitivity (or insensitivity) to accents, case, and punctuation;
treatment of digits within text; and many other options to satisfy a
variety of uses.
</p><p>
To include this additional collation information in a language tag,
append <code class="literal">-u</code>, which indicates there are additional
collation settings, followed by one or more
<code class="literal">-</code><em class="replaceable"><code>key</code></em><code class="literal">-</code><em class="replaceable"><code>value</code></em>
pairs. The <em class="replaceable"><code>key</code></em> is the key for a <a class="link" href="collation.html#ICU-COLLATION-SETTINGS" title="24.2.3.2. Collation Settings for an ICU Locale">collation setting</a> and
<em class="replaceable"><code>value</code></em> is a valid value for that setting. For
boolean settings, the <code class="literal">-</code><em class="replaceable"><code>key</code></em>
may be specified without a corresponding
<code class="literal">-</code><em class="replaceable"><code>value</code></em>, which implies a
value of <code class="literal">true</code>.
</p><p>
For example, the language tag <code class="literal">en-US-u-kn-ks-level2</code>
means the locale with the English language in the US region, with
collation settings <code class="literal">kn</code> set to <code class="literal">true</code>
and <code class="literal">ks</code> set to <code class="literal">level2</code>. Those
settings mean the collation will be case-insensitive and treat a sequence
of digits as a single number:
</p><pre class="screen">
CREATE COLLATION mycollation5 (provider = icu, deterministic = false, locale = 'en-US-u-kn-ks-level2');
SELECT 'aB' = 'Ab' COLLATE mycollation5 as result;
result
--------
t
(1 row)
SELECT 'N-45' < 'N-123' COLLATE mycollation5 as result;
result
--------
t
(1 row)
</pre><p>
</p><p>
See <a class="xref" href="collation.html#ICU-CUSTOM-COLLATIONS" title="24.2.3. ICU Custom Collations">Section 24.2.3</a> for details and additional
examples of using language tags with custom collation information for the
locale.
</p></div></div><div class="sect2" id="LOCALE-PROBLEMS"><div class="titlepage"><div><div><h3 class="title">24.1.6. Problems <a href="#LOCALE-PROBLEMS" class="id_link">#</a></h3></div></div></div><p>
If locale support doesn't work according to 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 can 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. The <code class="envar">LC_COLLATE</code> and <code class="envar">LC_CTYPE</code>
settings are determined when a database is created, and cannot be
changed except by creating a new database. 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 class="xref" href="nls.html" title="Chapter 57. Native Language Support">Chapter 57</a> or write to the developers'
mailing list.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="charset.html" title="Chapter 24. Localization">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="charset.html" title="Chapter 24. Localization">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="collation.html" title="24.2. Collation Support">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 24. Localization </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 24.2. Collation Support</td></tr></table></div></body></html>