Movatterモバイル変換

24.1.1. Overview

24.1.2. Behavior

24.1.3. Selecting Locales

24.1.4. Locale Providers

24.1.5. Problems

Locale support is automatically initialized when a database cluster is created usinginitdb.initdb 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 instructinitdb exactly which locale to use by specifying the--locale option. For example:

initdb --locale=sv_SE

This example for Unix systems sets the locale to Swedish (sv) as spoken in Sweden (SE). Other possibilities might includeen_US (U.S. English) andfr_CA (French Canadian). If more than one character set can be used for a locale then the specifications can take the formlanguage_territory.codeset. For example,fr_BE.UTF-8 represents the French language (fr) as spoken in Belgium (BE), with aUTF-8 character set encoding.

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 commandlocale -a will provide a list of available locales. Windows uses more verbose locale names, such asGerman_Germany orSwedish_Sweden.1252, but the principles are the same.

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:

The category names translate into names ofinitdb 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, useinitdb --locale=fr_CA --lc-monetary=en_US.

If you want the system to behave as if it had no locale support, use the special locale nameC, or equivalentlyPOSIX.

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.LC_COLLATE andLC_CTYPE 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 inSection 24.2.) The default values for these categories are determined wheninitdb is run, and those values are used when new databases are created, unless specified otherwise in theCREATE DATABASE command.

The other locale categories can be changed whenever desired by setting the server configuration parameters that have the same name as the locale categories (seeSection 20.11.2 for details). The values that are chosen byinitdb are actually only written into the configuration filepostgresql.conf to serve as defaults when the server is started. If you remove these assignments frompostgresql.conf then the server will inherit the settings from its execution environment.

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.

To enable messages to be translated to the user's preferred language,NLS must have been selected at build time (configure --enable-nls). All other locale support is built in automatically.

The locale settings influence the following SQL features:

The drawback of using locales other thanC orPOSIX inPostgreSQL is its performance impact. It slows character handling and prevents ordinary indexes from being used byLIKE. For this reason use locales only if you actually need them.

As a workaround to allowPostgreSQL to use indexes withLIKE 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 toSection 11.10 for more information. Another approach is to create indexes using theC collation, as discussed inSection 24.2.

Locales can be selected in different scopes depending on requirements. The above overview showed how locales are specified usinginitdb 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.

PostgreSQL supports multiplelocale providers. This specifies which library supplies the locale data. One standard provider name islibc, 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 isicu, which uses the external ICU library. ICU locales can only be used if support for ICU was configured when PostgreSQL was built.

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 thelibc provider, which is the default. Here is an example to initialize a database cluster using the ICU provider:

initdb --locale-provider=icu --icu-locale=en

See the description of the respective commands and programs for details. Note that you can mix locale providers at different granularities, for example uselibc by default for the cluster but have one database that uses theicu provider, and then have collation objects using either provider within those databases.

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.

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 commandlocale -a if your operating system provides it.

Check thatPostgreSQL is actually using the locale that you think it is. TheLC_COLLATE andLC_CTYPE settings are determined when a database is created, and cannot be changed except by creating a new database. Other locale settings includingLC_MESSAGES andLC_MONETARY 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 theSHOW command.

The directorysrc/test/locale in the source distribution contains a test suite forPostgreSQL's locale support.

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.

Maintaining catalogs of message translations requires the on-going efforts of many volunteers that want to seePostgreSQL 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 toChapter 57 or write to the developers' mailing list.