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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="LOCALE"
>22.1. Locale Support</A
></H1
><P
>   <I
CLASS="FIRSTTERM"
>Locale</I
> 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"
><H2
CLASS="SECT2"
><A
NAME="AEN31544"
>22.1.1. Overview</A
></H2
><P
>    Locale support is automatically initialized when a database
    cluster is created using <TT
CLASS="COMMAND"
>initdb</TT
>.
    <TT
CLASS="COMMAND"
>initdb</TT
> 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
    <TT
CLASS="COMMAND"
>initdb</TT
> exactly which locale to use by
    specifying the <TT
CLASS="OPTION"
>--locale</TT
> 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
    (<TT
CLASS="LITERAL"
>sv</TT
>) as spoken
    in Sweden (<TT
CLASS="LITERAL"
>SE</TT
>).  Other possibilities might include
    <TT
CLASS="LITERAL"
>en_US</TT
> (U.S. English) and <TT
CLASS="LITERAL"
>fr_CA</TT
> (French
    Canadian).  If more than one character set can be used for a
    locale then the specifications can take the form
    <TT
CLASS="REPLACEABLE"
><I
>language_territory.codeset</I
></TT
>.  For example,
    <TT
CLASS="LITERAL"
>fr_BE.UTF-8</TT
> 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
    <TT
CLASS="LITERAL"
>locale -a</TT
> will provide a list of available locales.
    Windows uses more verbose locale names, such as <TT
CLASS="LITERAL"
>German_Germany</TT
>
    or <TT
CLASS="LITERAL"
>Swedish_Sweden.1252</TT
>, 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:

    <DIV
CLASS="INFORMALTABLE"
><P
></P
><A
NAME="AEN31565"
></A
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><TBODY
><TR
><TD
><TT
CLASS="ENVAR"
>LC_COLLATE</TT
></TD
><TD
>String sort order</TD
></TR
><TR
><TD
><TT
CLASS="ENVAR"
>LC_CTYPE</TT
></TD
><TD
>Character classification (What is a letter? Its upper-case equivalent?)</TD
></TR
><TR
><TD
><TT
CLASS="ENVAR"
>LC_MESSAGES</TT
></TD
><TD
>Language of messages</TD
></TR
><TR
><TD
><TT
CLASS="ENVAR"
>LC_MONETARY</TT
></TD
><TD
>Formatting of currency amounts</TD
></TR
><TR
><TD
><TT
CLASS="ENVAR"
>LC_NUMERIC</TT
></TD
><TD
>Formatting of numbers</TD
></TR
><TR
><TD
><TT
CLASS="ENVAR"
>LC_TIME</TT
></TD
><TD
>Formatting of dates and times</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
>

    The category names translate into names of
    <TT
CLASS="COMMAND"
>initdb</TT
> 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
    <TT
CLASS="LITERAL"
>initdb --locale=fr_CA --lc-monetary=en_US</TT
>.
   </P
><P
>    If you want the system to behave as if it had no locale support,
    use the special locale name <TT
CLASS="LITERAL"
>C</TT
>, or equivalently
    <TT
CLASS="LITERAL"
>POSIX</TT
>.
   </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. <TT
CLASS="LITERAL"
>LC_COLLATE</TT
>
    and <TT
CLASS="LITERAL"
>LC_CTYPE</TT
> 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
HREF="collation.html"
>Section 22.2</A
>.)
    The default values for these
    categories are determined when <TT
CLASS="COMMAND"
>initdb</TT
> is run, and
    those values are used when new databases are created, unless
    specified otherwise in the <TT
CLASS="COMMAND"
>CREATE DATABASE</TT
> 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
HREF="runtime-config-client.html#RUNTIME-CONFIG-CLIENT-FORMAT"
>Section 18.11.2</A
> for details).  The values
    that are chosen by <TT
CLASS="COMMAND"
>initdb</TT
> are actually only written
    into the configuration file <TT
CLASS="FILENAME"
>postgresql.conf</TT
> to
    serve as defaults when the server is started.  If you remove these
    assignments from <TT
CLASS="FILENAME"
>postgresql.conf</TT
> 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"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>     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: <TT
CLASS="ENVAR"
>LC_ALL</TT
>, <TT
CLASS="ENVAR"
>LC_COLLATE</TT
>
     (or the variable corresponding to the respective category),
     <TT
CLASS="ENVAR"
>LANG</TT
>.  If none of these environment variables are
     set then the locale defaults to <TT
CLASS="LITERAL"
>C</TT
>.
    </P
><P
>     Some message localization libraries also look at the environment
     variable <TT
CLASS="ENVAR"
>LANGUAGE</TT
> 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
></BLOCKQUOTE
></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
    (<TT
CLASS="LITERAL"
>configure --enable-nls</TT
>).  All other locale support is
    built in automatically.
   </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN31621"
>22.1.2. Behavior</A
></H2
><P
>    The locale settings influence the following SQL features:

    <P
></P
></P><UL
><LI
><P
>       Sort order in queries using <TT
CLASS="LITERAL"
>ORDER BY</TT
> or the standard
       comparison operators on textual data
       
      </P
></LI
><LI
><P
>       The <CODE
CLASS="FUNCTION"
>upper</CODE
>, <CODE
CLASS="FUNCTION"
>lower</CODE
>, and <CODE
CLASS="FUNCTION"
>initcap</CODE
>
       functions
       
       
      </P
></LI
><LI
><P
>       Pattern matching operators (<TT
CLASS="LITERAL"
>LIKE</TT
>, <TT
CLASS="LITERAL"
>SIMILAR TO</TT
>,
       and POSIX-style regular expressions); locales affect both case
       insensitive matching and the classification of characters by
       character-class regular expressions
       
       
      </P
></LI
><LI
><P
>       The <CODE
CLASS="FUNCTION"
>to_char</CODE
> family of functions
       
      </P
></LI
><LI
><P
>       The ability to use indexes with <TT
CLASS="LITERAL"
>LIKE</TT
> clauses
      </P
></LI
></UL
><P>
   </P
><P
>    The drawback of using locales other than <TT
CLASS="LITERAL"
>C</TT
> or
    <TT
CLASS="LITERAL"
>POSIX</TT
> in <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> is its performance
    impact. It slows character handling and prevents ordinary indexes
    from being used by <TT
CLASS="LITERAL"
>LIKE</TT
>. 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 <TT
CLASS="LITERAL"
>LIKE</TT
> 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"
>Section 11.9</A
>
    for more information.  Another approach is to create indexes using
    the <TT
CLASS="LITERAL"
>C</TT
> collation, as discussed in
    <A
HREF="collation.html"
>Section 22.2</A
>.
   </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN31672"
>22.1.3. Problems</A
></H2
><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 <TT
CLASS="LITERAL"
>locale -a</TT
> 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 <TT
CLASS="ENVAR"
>LC_COLLATE</TT
> and <TT
CLASS="ENVAR"
>LC_CTYPE</TT
>
    settings are determined when a database is created, and cannot be
    changed except by creating a new database.  Other locale
    settings including <TT
CLASS="ENVAR"
>LC_MESSAGES</TT
> and <TT
CLASS="ENVAR"
>LC_MONETARY</TT
>
    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 <TT
CLASS="COMMAND"
>SHOW</TT
> command.
   </P
><P
>    The directory <TT
CLASS="FILENAME"
>src/test/locale</TT
> 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"
>Chapter 48</A
> or write to the developers'
    mailing list.
   </P
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