1541 lines
54 KiB
Plaintext
1541 lines
54 KiB
Plaintext
<!-- doc/src/sgml/charset.sgml -->
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<chapter id="charset">
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<title>Localization</title>
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<para>
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This chapter describes the available localization features from the
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point of view of the administrator.
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<productname>PostgreSQL</productname> supports two localization
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facilities:
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<itemizedlist>
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<listitem>
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<para>
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Using the locale features of the operating system to provide
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locale-specific collation order, number formatting, translated
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messages, and other aspects.
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This is covered in <xref linkend="locale"> and
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<xref linkend="collation">.
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</para>
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</listitem>
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<listitem>
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<para>
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Providing a number of different character sets to support storing text
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in all kinds of languages, and providing character set translation
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between client and server.
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This is covered in <xref linkend="multibyte">.
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</para>
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</listitem>
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</itemizedlist>
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</para>
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<sect1 id="locale">
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<title>Locale Support</title>
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<indexterm zone="locale"><primary>locale</></>
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<para>
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<firstterm>Locale</> support refers to an application respecting
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cultural preferences regarding alphabets, sorting, number
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formatting, etc. <productname>PostgreSQL</> uses the standard ISO
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C and <acronym>POSIX</acronym> locale facilities provided by the server operating
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system. For additional information refer to the documentation of your
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system.
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</para>
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<sect2>
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<title>Overview</title>
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<para>
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Locale support is automatically initialized when a database
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cluster is created using <command>initdb</command>.
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<command>initdb</command> will initialize the database cluster
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with the locale setting of its execution environment by default,
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so if your system is already set to use the locale that you want
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in your database cluster then there is nothing else you need to
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do. If you want to use a different locale (or you are not sure
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which locale your system is set to), you can instruct
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<command>initdb</command> exactly which locale to use by
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specifying the <option>--locale</option> option. For example:
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<screen>
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initdb --locale=sv_SE
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</screen>
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</para>
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<para>
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This example for Unix systems sets the locale to Swedish
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(<literal>sv</>) as spoken
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in Sweden (<literal>SE</>). Other possibilities might include
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<literal>en_US</> (U.S. English) and <literal>fr_CA</> (French
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Canadian). If more than one character set can be used for a
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locale then the specifications can take the form
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<replaceable>language_territory.codeset</>. For example,
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<literal>fr_BE.UTF-8</> represents the French language (fr) as
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spoken in Belgium (BE), with a <acronym>UTF-8</> character set
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encoding.
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</para>
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<para>
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What locales are available on your
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system under what names depends on what was provided by the operating
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system vendor and what was installed. On most Unix systems, the command
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<literal>locale -a</> will provide a list of available locales.
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Windows uses more verbose locale names, such as <literal>German_Germany</>
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or <literal>Swedish_Sweden.1252</>, but the principles are the same.
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</para>
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<para>
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Occasionally it is useful to mix rules from several locales, e.g.,
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use English collation rules but Spanish messages. To support that, a
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set of locale subcategories exist that control only certain
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aspects of the localization rules:
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<informaltable>
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<tgroup cols="2">
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<tbody>
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<row>
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<entry><envar>LC_COLLATE</></>
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<entry>String sort order</>
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</row>
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<row>
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<entry><envar>LC_CTYPE</></>
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<entry>Character classification (What is a letter? Its upper-case equivalent?)</>
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</row>
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<row>
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<entry><envar>LC_MESSAGES</></>
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<entry>Language of messages</>
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</row>
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<row>
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<entry><envar>LC_MONETARY</></>
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<entry>Formatting of currency amounts</>
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</row>
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<row>
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<entry><envar>LC_NUMERIC</></>
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<entry>Formatting of numbers</>
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</row>
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<row>
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<entry><envar>LC_TIME</></>
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<entry>Formatting of dates and times</>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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The category names translate into names of
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<command>initdb</command> options to override the locale choice
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for a specific category. For instance, to set the locale to
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French Canadian, but use U.S. rules for formatting currency, use
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<literal>initdb --locale=fr_CA --lc-monetary=en_US</literal>.
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</para>
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<para>
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If you want the system to behave as if it had no locale support,
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use the special locale name <literal>C</>, or equivalently
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<literal>POSIX</>.
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</para>
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<para>
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Some locale categories must have their values
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fixed when the database is created. You can use different settings
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for different databases, but once a database is created, you cannot
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change them for that database anymore. <literal>LC_COLLATE</literal>
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and <literal>LC_CTYPE</literal> are these categories. They affect
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the sort order of indexes, so they must be kept fixed, or indexes on
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text columns would become corrupt.
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(But you can alleviate this restriction using collations, as discussed
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in <xref linkend="collation">.)
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The default values for these
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categories are determined when <command>initdb</command> is run, and
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those values are used when new databases are created, unless
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specified otherwise in the <command>CREATE DATABASE</command> command.
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</para>
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<para>
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The other locale categories can be changed whenever desired
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by setting the server configuration parameters
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that have the same name as the locale categories (see <xref
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linkend="runtime-config-client-format"> for details). The values
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that are chosen by <command>initdb</command> are actually only written
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into the configuration file <filename>postgresql.conf</filename> to
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serve as defaults when the server is started. If you remove these
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assignments from <filename>postgresql.conf</filename> then the
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server will inherit the settings from its execution environment.
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</para>
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<para>
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Note that the locale behavior of the server is determined by the
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environment variables seen by the server, not by the environment
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of any client. Therefore, be careful to configure the correct locale settings
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before starting the server. A consequence of this is that if
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client and server are set up in different locales, messages might
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appear in different languages depending on where they originated.
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</para>
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<note>
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<para>
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When we speak of inheriting the locale from the execution
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environment, this means the following on most operating systems:
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For a given locale category, say the collation, the following
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environment variables are consulted in this order until one is
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found to be set: <envar>LC_ALL</envar>, <envar>LC_COLLATE</envar>
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(or the variable corresponding to the respective category),
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<envar>LANG</envar>. If none of these environment variables are
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set then the locale defaults to <literal>C</literal>.
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</para>
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<para>
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Some message localization libraries also look at the environment
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variable <envar>LANGUAGE</envar> which overrides all other locale
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settings for the purpose of setting the language of messages. If
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in doubt, please refer to the documentation of your operating
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system, in particular the documentation about
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<application>gettext</>.
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</para>
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</note>
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<para>
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To enable messages to be translated to the user's preferred language,
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<acronym>NLS</acronym> must have been selected at build time
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(<literal>configure --enable-nls</>). All other locale support is
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built in automatically.
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</para>
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</sect2>
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<sect2>
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<title>Behavior</title>
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<para>
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The locale settings influence the following SQL features:
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<itemizedlist>
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<listitem>
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<para>
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Sort order in queries using <literal>ORDER BY</> or the standard
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comparison operators on textual data
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<indexterm><primary>ORDER BY</><secondary>and locales</></indexterm>
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</para>
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</listitem>
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<listitem>
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<para>
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The <function>upper</>, <function>lower</>, and <function>initcap</>
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functions
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<indexterm><primary>upper</><secondary>and locales</></indexterm>
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<indexterm><primary>lower</><secondary>and locales</></indexterm>
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</para>
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</listitem>
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<listitem>
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<para>
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Pattern matching operators (<literal>LIKE</>, <literal>SIMILAR TO</>,
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and POSIX-style regular expressions); locales affect both case
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insensitive matching and the classification of characters by
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character-class regular expressions
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<indexterm><primary>LIKE</><secondary>and locales</></indexterm>
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<indexterm><primary>regular expressions</><secondary>and locales</></indexterm>
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</para>
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</listitem>
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<listitem>
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<para>
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The <function>to_char</> family of functions
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<indexterm><primary>to_char</><secondary>and locales</></indexterm>
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</para>
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</listitem>
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<listitem>
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<para>
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The ability to use indexes with <literal>LIKE</> clauses
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</para>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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The drawback of using locales other than <literal>C</> or
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<literal>POSIX</> in <productname>PostgreSQL</> is its performance
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impact. It slows character handling and prevents ordinary indexes
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from being used by <literal>LIKE</>. For this reason use locales
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only if you actually need them.
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</para>
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<para>
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As a workaround to allow <productname>PostgreSQL</> to use indexes
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with <literal>LIKE</> clauses under a non-C locale, several custom
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operator classes exist. These allow the creation of an index that
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performs a strict character-by-character comparison, ignoring
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locale comparison rules. Refer to <xref linkend="indexes-opclass">
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for more information. Another approach is to create indexes using
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the <literal>C</> collation, as discussed in
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<xref linkend="collation">.
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</para>
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</sect2>
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<sect2>
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<title>Problems</title>
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<para>
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If locale support doesn't work according to the explanation above,
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check that the locale support in your operating system is
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correctly configured. To check what locales are installed on your
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system, you can use the command <literal>locale -a</literal> if
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your operating system provides it.
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</para>
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<para>
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Check that <productname>PostgreSQL</> is actually using the locale
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that you think it is. The <envar>LC_COLLATE</> and <envar>LC_CTYPE</>
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settings are determined when a database is created, and cannot be
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changed except by creating a new database. Other locale
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settings including <envar>LC_MESSAGES</> and <envar>LC_MONETARY</>
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are initially determined by the environment the server is started
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in, but can be changed on-the-fly. You can check the active locale
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settings using the <command>SHOW</> command.
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</para>
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<para>
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The directory <filename>src/test/locale</> in the source
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distribution contains a test suite for
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<productname>PostgreSQL</>'s locale support.
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</para>
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<para>
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Client applications that handle server-side errors by parsing the
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text of the error message will obviously have problems when the
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server's messages are in a different language. Authors of such
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applications are advised to make use of the error code scheme
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instead.
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</para>
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<para>
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Maintaining catalogs of message translations requires the on-going
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efforts of many volunteers that want to see
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<productname>PostgreSQL</> speak their preferred language well.
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If messages in your language are currently not available or not fully
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translated, your assistance would be appreciated. If you want to
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help, refer to <xref linkend="nls"> or write to the developers'
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mailing list.
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</para>
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</sect2>
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</sect1>
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<sect1 id="collation">
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<title>Collation Support</title>
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<indexterm zone="collation"><primary>collation</></>
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<para>
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The collation feature allows specifying the sort order and character
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classification behavior of data per-column, or even per-operation.
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This alleviates the restriction that the
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<symbol>LC_COLLATE</symbol> and <symbol>LC_CTYPE</symbol> settings
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of a database cannot be changed after its creation.
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</para>
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<sect2>
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<title>Concepts</title>
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<para>
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Conceptually, every expression of a collatable data type has a
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collation. (The built-in collatable data types are
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<type>text</type>, <type>varchar</type>, and <type>char</type>.
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User-defined base types can also be marked collatable, and of course
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a domain over a collatable data type is collatable.) If the
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expression is a column reference, the collation of the expression is the
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defined collation of the column. If the expression is a constant, the
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collation is the default collation of the data type of the
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constant. The collation of a more complex expression is derived
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from the collations of its inputs, as described below.
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</para>
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<para>
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The collation of an expression can be the <quote>default</quote>
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collation, which means the locale settings defined for the
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database. It is also possible for an expression's collation to be
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indeterminate. In such cases, ordering operations and other
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operations that need to know the collation will fail.
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</para>
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<para>
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When the database system has to perform an ordering or a character
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classification, it uses the collation of the input expression. This
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happens, for example, with <literal>ORDER BY</literal> clauses
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and function or operator calls such as <literal><</literal>.
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The collation to apply for an <literal>ORDER BY</literal> clause
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is simply the collation of the sort key. The collation to apply for a
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function or operator call is derived from the arguments, as described
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below. In addition to comparison operators, collations are taken into
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account by functions that convert between lower and upper case
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letters, such as <function>lower</>, <function>upper</>, and
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<function>initcap</>; by pattern matching operators; and by
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<function>to_char</> and related functions.
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</para>
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<para>
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For a function or operator call, the collation that is derived by
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examining the argument collations is used at run time for performing
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the specified operation. If the result of the function or operator
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call is of a collatable data type, the collation is also used at parse
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time as the defined collation of the function or operator expression,
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in case there is a surrounding expression that requires knowledge of
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its collation.
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</para>
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<para>
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The <firstterm>collation derivation</firstterm> of an expression can be
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implicit or explicit. This distinction affects how collations are
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combined when multiple different collations appear in an
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expression. An explicit collation derivation occurs when a
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<literal>COLLATE</literal> clause is used; all other collation
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derivations are implicit. When multiple collations need to be
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combined, for example in a function call, the following rules are
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used:
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<orderedlist>
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<listitem>
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<para>
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If any input expression has an explicit collation derivation, then
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all explicitly derived collations among the input expressions must be
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the same, otherwise an error is raised. If any explicitly
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derived collation is present, that is the result of the
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collation combination.
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</para>
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</listitem>
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<listitem>
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<para>
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Otherwise, all input expressions must have the same implicit
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collation derivation or the default collation. If any non-default
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collation is present, that is the result of the collation combination.
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Otherwise, the result is the default collation.
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</para>
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</listitem>
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<listitem>
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<para>
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If there are conflicting non-default implicit collations among the
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input expressions, then the combination is deemed to have indeterminate
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collation. This is not an error condition unless the particular
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function being invoked requires knowledge of the collation it should
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apply. If it does, an error will be raised at run-time.
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</para>
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</listitem>
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</orderedlist>
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For example, consider this table definition:
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<programlisting>
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CREATE TABLE test1 (
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a text COLLATE "de_DE",
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b text COLLATE "es_ES",
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...
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);
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</programlisting>
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Then in
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<programlisting>
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SELECT a < 'foo' FROM test1;
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</programlisting>
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the <literal><</literal> comparison is performed according to
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<literal>de_DE</literal> rules, because the expression combines an
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implicitly derived collation with the default collation. But in
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<programlisting>
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SELECT a < ('foo' COLLATE "fr_FR") FROM test1;
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</programlisting>
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the comparison is performed using <literal>fr_FR</literal> rules,
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because the explicit collation derivation overrides the implicit one.
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Furthermore, given
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<programlisting>
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SELECT a < b FROM test1;
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</programlisting>
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the parser cannot determine which collation to apply, since the
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<structfield>a</> and <structfield>b</> columns have conflicting
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implicit collations. Since the <literal><</literal> operator
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does need to know which collation to use, this will result in an
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error. The error can be resolved by attaching an explicit collation
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specifier to either input expression, thus:
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<programlisting>
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SELECT a < b COLLATE "de_DE" FROM test1;
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</programlisting>
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or equivalently
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<programlisting>
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SELECT a COLLATE "de_DE" < b FROM test1;
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</programlisting>
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On the other hand, the structurally similar case
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<programlisting>
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SELECT a || b FROM test1;
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</programlisting>
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does not result in an error, because the <literal>||</> operator
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does not care about collations: its result is the same regardless
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of the collation.
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</para>
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<para>
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The collation assigned to a function or operator's combined input
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expressions is also considered to apply to the function or operator's
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result, if the function or operator delivers a result of a collatable
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data type. So, in
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<programlisting>
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SELECT * FROM test1 ORDER BY a || 'foo';
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</programlisting>
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the ordering will be done according to <literal>de_DE</literal> rules.
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But this query:
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<programlisting>
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SELECT * FROM test1 ORDER BY a || b;
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</programlisting>
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results in an error, because even though the <literal>||</> operator
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doesn't need to know a collation, the <literal>ORDER BY</> clause does.
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As before, the conflict can be resolved with an explicit collation
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specifier:
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<programlisting>
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SELECT * FROM test1 ORDER BY a || b COLLATE "fr_FR";
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</programlisting>
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</para>
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</sect2>
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<sect2>
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<title>Managing Collations</title>
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|
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<para>
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A collation is an SQL schema object that maps an SQL name to
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operating system locales. In particular, it maps to a combination
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of <symbol>LC_COLLATE</symbol> and <symbol>LC_CTYPE</symbol>. (As
|
|
the name would suggest, the main purpose of a collation is to set
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<symbol>LC_COLLATE</symbol>, which controls the sort order. But
|
|
it is rarely necessary in practice to have an
|
|
<symbol>LC_CTYPE</symbol> setting that is different from
|
|
<symbol>LC_COLLATE</symbol>, so it is more convenient to collect
|
|
these under one concept than to create another infrastructure for
|
|
setting <symbol>LC_CTYPE</symbol> per expression.) Also, a collation
|
|
is tied to a character set encoding (see <xref linkend="multibyte">).
|
|
The same collation name may exist for different encodings.
|
|
</para>
|
|
|
|
<para>
|
|
On all platforms, the collations named <literal>default</>,
|
|
<literal>C</>, and <literal>POSIX</> are available. Additional
|
|
collations may be available depending on operating system support.
|
|
The <literal>default</> collation selects the <symbol>LC_COLLATE</symbol>
|
|
and <symbol>LC_CTYPE</symbol> values specified at database creation time.
|
|
The <literal>C</> and <literal>POSIX</> collations both specify
|
|
<quote>traditional C</> behavior, in which only the ASCII letters
|
|
<quote><literal>A</></quote> through <quote><literal>Z</></quote>
|
|
are treated as letters, and sorting is done strictly by character
|
|
code byte values.
|
|
</para>
|
|
|
|
<para>
|
|
If the operating system provides support for using multiple locales
|
|
within a single program (<function>newlocale</> and related functions),
|
|
then when a database cluster is initialized, <command>initdb</command>
|
|
populates the system catalog <literal>pg_collation</literal> with
|
|
collations based on all the locales it finds on the operating
|
|
system at the time. For example, the operating system might
|
|
provide a locale named <literal>de_DE.utf8</literal>.
|
|
<command>initdb</command> would then create a collation named
|
|
<literal>de_DE.utf8</literal> for encoding <literal>UTF8</literal>
|
|
that has both <symbol>LC_COLLATE</symbol> and
|
|
<symbol>LC_CTYPE</symbol> set to <literal>de_DE.utf8</literal>.
|
|
It will also create a collation with the <literal>.utf8</literal>
|
|
tag stripped off the name. So you could also use the collation
|
|
under the name <literal>de_DE</literal>, which is less cumbersome
|
|
to write and makes the name less encoding-dependent. Note that,
|
|
nevertheless, the initial set of collation names is
|
|
platform-dependent.
|
|
</para>
|
|
|
|
<para>
|
|
In case a collation is needed that has different values for
|
|
<symbol>LC_COLLATE</symbol> and <symbol>LC_CTYPE</symbol>, a new
|
|
collation may be created using
|
|
the <xref linkend="sql-createcollation"> command. That command
|
|
can also be used to create a new collation from an existing
|
|
collation, which can be useful to be able to use
|
|
operating-system-independent collation names in applications.
|
|
</para>
|
|
|
|
<para>
|
|
Within any particular database, only collations that use that
|
|
database's encoding are of interest. Other entries in
|
|
<literal>pg_collation</literal> are ignored. Thus, a stripped collation
|
|
name such as <literal>de_DE</literal> can be considered unique
|
|
within a given database even though it would not be unique globally.
|
|
Use of the stripped collation names is recommended, since it will
|
|
make one less thing you need to change if you decide to change to
|
|
another database encoding. Note however that the <literal>default</>,
|
|
<literal>C</>, and <literal>POSIX</> collations can be used
|
|
regardless of the database encoding.
|
|
</para>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> considers distinct collation
|
|
objects to be incompatible even when they have identical properties.
|
|
Thus for example,
|
|
<programlisting>
|
|
SELECT a COLLATE "C" < b COLLATE "POSIX" FROM test1;
|
|
</programlisting>
|
|
will draw an error even though the <literal>C</> and <literal>POSIX</>
|
|
collations have identical behaviors. Mixing stripped and non-stripped
|
|
collation names is therefore not recommended.
|
|
</para>
|
|
</sect2>
|
|
</sect1>
|
|
|
|
<sect1 id="multibyte">
|
|
<title>Character Set Support</title>
|
|
|
|
<indexterm zone="multibyte"><primary>character set</></>
|
|
|
|
<para>
|
|
The character set support in <productname>PostgreSQL</productname>
|
|
allows you to store text in a variety of character sets (also called
|
|
encodings), including
|
|
single-byte character sets such as the ISO 8859 series and
|
|
multiple-byte character sets such as <acronym>EUC</> (Extended Unix
|
|
Code), UTF-8, and Mule internal code. All supported character sets
|
|
can be used transparently by clients, but a few are not supported
|
|
for use within the server (that is, as a server-side encoding).
|
|
The default character set is selected while
|
|
initializing your <productname>PostgreSQL</productname> database
|
|
cluster using <command>initdb</>. It can be overridden when you
|
|
create a database, so you can have multiple
|
|
databases each with a different character set.
|
|
</para>
|
|
|
|
<para>
|
|
An important restriction, however, is that each database's character set
|
|
must be compatible with the database's <envar>LC_CTYPE</> (character
|
|
classification) and <envar>LC_COLLATE</> (string sort order) locale
|
|
settings. For <literal>C</> or
|
|
<literal>POSIX</> locale, any character set is allowed, but for other
|
|
locales there is only one character set that will work correctly.
|
|
(On Windows, however, UTF-8 encoding can be used with any locale.)
|
|
</para>
|
|
|
|
<sect2 id="multibyte-charset-supported">
|
|
<title>Supported Character Sets</title>
|
|
|
|
<para>
|
|
<xref linkend="charset-table"> shows the character sets available
|
|
for use in <productname>PostgreSQL</productname>.
|
|
</para>
|
|
|
|
<table id="charset-table">
|
|
<title><productname>PostgreSQL</productname> Character Sets</title>
|
|
<tgroup cols="6">
|
|
<thead>
|
|
<row>
|
|
<entry>Name</entry>
|
|
<entry>Description</entry>
|
|
<entry>Language</entry>
|
|
<entry>Server?</entry>
|
|
<!--
|
|
The Bytes/Char field is populated by looking at the values returned
|
|
by pg_wchar_table.mblen function for each encoding.
|
|
-->
|
|
<entry>Bytes/Char</entry>
|
|
<entry>Aliases</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>BIG5</literal></entry>
|
|
<entry>Big Five</entry>
|
|
<entry>Traditional Chinese</entry>
|
|
<entry>No</entry>
|
|
<entry>1-2</entry>
|
|
<entry><literal>WIN950</>, <literal>Windows950</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>EUC_CN</literal></entry>
|
|
<entry>Extended UNIX Code-CN</entry>
|
|
<entry>Simplified Chinese</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1-3</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>EUC_JP</literal></entry>
|
|
<entry>Extended UNIX Code-JP</entry>
|
|
<entry>Japanese</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1-3</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>EUC_JIS_2004</literal></entry>
|
|
<entry>Extended UNIX Code-JP, JIS X 0213</entry>
|
|
<entry>Japanese</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1-3</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>EUC_KR</literal></entry>
|
|
<entry>Extended UNIX Code-KR</entry>
|
|
<entry>Korean</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1-3</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>EUC_TW</literal></entry>
|
|
<entry>Extended UNIX Code-TW</entry>
|
|
<entry>Traditional Chinese, Taiwanese</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1-3</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>GB18030</literal></entry>
|
|
<entry>National Standard</entry>
|
|
<entry>Chinese</entry>
|
|
<entry>No</entry>
|
|
<entry>1-4</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>GBK</literal></entry>
|
|
<entry>Extended National Standard</entry>
|
|
<entry>Simplified Chinese</entry>
|
|
<entry>No</entry>
|
|
<entry>1-2</entry>
|
|
<entry><literal>WIN936</>, <literal>Windows936</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>ISO_8859_5</literal></entry>
|
|
<entry>ISO 8859-5, <acronym>ECMA</> 113</entry>
|
|
<entry>Latin/Cyrillic</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>ISO_8859_6</literal></entry>
|
|
<entry>ISO 8859-6, <acronym>ECMA</> 114</entry>
|
|
<entry>Latin/Arabic</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>ISO_8859_7</literal></entry>
|
|
<entry>ISO 8859-7, <acronym>ECMA</> 118</entry>
|
|
<entry>Latin/Greek</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>ISO_8859_8</literal></entry>
|
|
<entry>ISO 8859-8, <acronym>ECMA</> 121</entry>
|
|
<entry>Latin/Hebrew</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>JOHAB</literal></entry>
|
|
<entry><acronym>JOHAB</></entry>
|
|
<entry>Korean (Hangul)</entry>
|
|
<entry>No</entry>
|
|
<entry>1-3</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>KOI8R</literal></entry>
|
|
<entry><acronym>KOI</acronym>8-R</entry>
|
|
<entry>Cyrillic (Russian)</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>KOI8</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>KOI8U</literal></entry>
|
|
<entry><acronym>KOI</acronym>8-U</entry>
|
|
<entry>Cyrillic (Ukrainian)</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN1</literal></entry>
|
|
<entry>ISO 8859-1, <acronym>ECMA</> 94</entry>
|
|
<entry>Western European</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ISO88591</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN2</literal></entry>
|
|
<entry>ISO 8859-2, <acronym>ECMA</> 94</entry>
|
|
<entry>Central European</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ISO88592</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN3</literal></entry>
|
|
<entry>ISO 8859-3, <acronym>ECMA</> 94</entry>
|
|
<entry>South European</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ISO88593</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN4</literal></entry>
|
|
<entry>ISO 8859-4, <acronym>ECMA</> 94</entry>
|
|
<entry>North European</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ISO88594</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN5</literal></entry>
|
|
<entry>ISO 8859-9, <acronym>ECMA</> 128</entry>
|
|
<entry>Turkish</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ISO88599</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN6</literal></entry>
|
|
<entry>ISO 8859-10, <acronym>ECMA</> 144</entry>
|
|
<entry>Nordic</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ISO885910</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN7</literal></entry>
|
|
<entry>ISO 8859-13</entry>
|
|
<entry>Baltic</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ISO885913</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN8</literal></entry>
|
|
<entry>ISO 8859-14</entry>
|
|
<entry>Celtic</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ISO885914</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN9</literal></entry>
|
|
<entry>ISO 8859-15</entry>
|
|
<entry>LATIN1 with Euro and accents</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ISO885915</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN10</literal></entry>
|
|
<entry>ISO 8859-16, <acronym>ASRO</> SR 14111</entry>
|
|
<entry>Romanian</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ISO885916</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>MULE_INTERNAL</literal></entry>
|
|
<entry>Mule internal code</entry>
|
|
<entry>Multilingual Emacs</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1-4</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>SJIS</literal></entry>
|
|
<entry>Shift JIS</entry>
|
|
<entry>Japanese</entry>
|
|
<entry>No</entry>
|
|
<entry>1-2</entry>
|
|
<entry><literal>Mskanji</>, <literal>ShiftJIS</>, <literal>WIN932</>, <literal>Windows932</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>SHIFT_JIS_2004</literal></entry>
|
|
<entry>Shift JIS, JIS X 0213</entry>
|
|
<entry>Japanese</entry>
|
|
<entry>No</entry>
|
|
<entry>1-2</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>SQL_ASCII</literal></entry>
|
|
<entry>unspecified (see text)</entry>
|
|
<entry><emphasis>any</></entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>UHC</literal></entry>
|
|
<entry>Unified Hangul Code</entry>
|
|
<entry>Korean</entry>
|
|
<entry>No</entry>
|
|
<entry>1-2</entry>
|
|
<entry><literal>WIN949</>, <literal>Windows949</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>UTF8</literal></entry>
|
|
<entry>Unicode, 8-bit</entry>
|
|
<entry><emphasis>all</></entry>
|
|
<entry>Yes</entry>
|
|
<entry>1-4</entry>
|
|
<entry><literal>Unicode</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN866</literal></entry>
|
|
<entry>Windows CP866</entry>
|
|
<entry>Cyrillic</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ALT</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN874</literal></entry>
|
|
<entry>Windows CP874</entry>
|
|
<entry>Thai</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1250</literal></entry>
|
|
<entry>Windows CP1250</entry>
|
|
<entry>Central European</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1251</literal></entry>
|
|
<entry>Windows CP1251</entry>
|
|
<entry>Cyrillic</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>WIN</></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1252</literal></entry>
|
|
<entry>Windows CP1252</entry>
|
|
<entry>Western European</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1253</literal></entry>
|
|
<entry>Windows CP1253</entry>
|
|
<entry>Greek</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1254</literal></entry>
|
|
<entry>Windows CP1254</entry>
|
|
<entry>Turkish</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1255</literal></entry>
|
|
<entry>Windows CP1255</entry>
|
|
<entry>Hebrew</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1256</literal></entry>
|
|
<entry>Windows CP1256</entry>
|
|
<entry>Arabic</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1257</literal></entry>
|
|
<entry>Windows CP1257</entry>
|
|
<entry>Baltic</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry></entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1258</literal></entry>
|
|
<entry>Windows CP1258</entry>
|
|
<entry>Vietnamese</entry>
|
|
<entry>Yes</entry>
|
|
<entry>1</entry>
|
|
<entry><literal>ABC</>, <literal>TCVN</>, <literal>TCVN5712</>, <literal>VSCII</></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
Not all client <acronym>API</>s support all the listed character sets. For example, the
|
|
<productname>PostgreSQL</>
|
|
JDBC driver does not support <literal>MULE_INTERNAL</>, <literal>LATIN6</>,
|
|
<literal>LATIN8</>, and <literal>LATIN10</>.
|
|
</para>
|
|
|
|
<para>
|
|
The <literal>SQL_ASCII</> setting behaves considerably differently
|
|
from the other settings. When the server character set is
|
|
<literal>SQL_ASCII</>, the server interprets byte values 0-127
|
|
according to the ASCII standard, while byte values 128-255 are taken
|
|
as uninterpreted characters. No encoding conversion will be done when
|
|
the setting is <literal>SQL_ASCII</>. Thus, this setting is not so
|
|
much a declaration that a specific encoding is in use, as a declaration
|
|
of ignorance about the encoding. In most cases, if you are
|
|
working with any non-ASCII data, it is unwise to use the
|
|
<literal>SQL_ASCII</> setting because
|
|
<productname>PostgreSQL</productname> will be unable to help you by
|
|
converting or validating non-ASCII characters.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Setting the Character Set</title>
|
|
|
|
<para>
|
|
<command>initdb</> defines the default character set (encoding)
|
|
for a <productname>PostgreSQL</productname> cluster. For example,
|
|
|
|
<screen>
|
|
initdb -E EUC_JP
|
|
</screen>
|
|
|
|
sets the default character set to
|
|
<literal>EUC_JP</literal> (Extended Unix Code for Japanese). You
|
|
can use <option>--encoding</option> instead of
|
|
<option>-E</option> if you prefer longer option strings.
|
|
If no <option>-E</> or <option>--encoding</option> option is
|
|
given, <command>initdb</> attempts to determine the appropriate
|
|
encoding to use based on the specified or default locale.
|
|
</para>
|
|
|
|
<para>
|
|
You can specify a non-default encoding at database creation time,
|
|
provided that the encoding is compatible with the selected locale:
|
|
|
|
<screen>
|
|
createdb -E EUC_KR -T template0 --lc-collate=ko_KR.euckr --lc-ctype=ko_KR.euckr korean
|
|
</screen>
|
|
|
|
This will create a database named <literal>korean</literal> that
|
|
uses the character set <literal>EUC_KR</literal>, and locale <literal>ko_KR</literal>.
|
|
Another way to accomplish this is to use this SQL command:
|
|
|
|
<programlisting>
|
|
CREATE DATABASE korean WITH ENCODING 'EUC_KR' LC_COLLATE='ko_KR.euckr' LC_CTYPE='ko_KR.euckr' TEMPLATE=template0;
|
|
</programlisting>
|
|
|
|
Notice that the above commands specify copying the <literal>template0</>
|
|
database. When copying any other database, the encoding and locale
|
|
settings cannot be changed from those of the source database, because
|
|
that might result in corrupt data. For more information see
|
|
<xref linkend="manage-ag-templatedbs">.
|
|
</para>
|
|
|
|
<para>
|
|
The encoding for a database is stored in the system catalog
|
|
<literal>pg_database</literal>. You can see it by using the
|
|
<command>psql</command> <option>-l</option> option or the
|
|
<command>\l</command> command.
|
|
|
|
<screen>
|
|
$ <userinput>psql -l</userinput>
|
|
List of databases
|
|
Name | Owner | Encoding | Collation | Ctype | Access Privileges
|
|
-----------+----------+-----------+-------------+-------------+-------------------------------------
|
|
clocaledb | hlinnaka | SQL_ASCII | C | C |
|
|
englishdb | hlinnaka | UTF8 | en_GB.UTF8 | en_GB.UTF8 |
|
|
japanese | hlinnaka | UTF8 | ja_JP.UTF8 | ja_JP.UTF8 |
|
|
korean | hlinnaka | EUC_KR | ko_KR.euckr | ko_KR.euckr |
|
|
postgres | hlinnaka | UTF8 | fi_FI.UTF8 | fi_FI.UTF8 |
|
|
template0 | hlinnaka | UTF8 | fi_FI.UTF8 | fi_FI.UTF8 | {=c/hlinnaka,hlinnaka=CTc/hlinnaka}
|
|
template1 | hlinnaka | UTF8 | fi_FI.UTF8 | fi_FI.UTF8 | {=c/hlinnaka,hlinnaka=CTc/hlinnaka}
|
|
(7 rows)
|
|
</screen>
|
|
</para>
|
|
|
|
<important>
|
|
<para>
|
|
On most modern operating systems, <productname>PostgreSQL</productname>
|
|
can determine which character set is implied by the <envar>LC_CTYPE</>
|
|
setting, and it will enforce that only the matching database encoding is
|
|
used. On older systems it is your responsibility to ensure that you use
|
|
the encoding expected by the locale you have selected. A mistake in
|
|
this area is likely to lead to strange behavior of locale-dependent
|
|
operations such as sorting.
|
|
</para>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> will allow superusers to create
|
|
databases with <literal>SQL_ASCII</> encoding even when
|
|
<envar>LC_CTYPE</> is not <literal>C</> or <literal>POSIX</>. As noted
|
|
above, <literal>SQL_ASCII</> does not enforce that the data stored in
|
|
the database has any particular encoding, and so this choice poses risks
|
|
of locale-dependent misbehavior. Using this combination of settings is
|
|
deprecated and may someday be forbidden altogether.
|
|
</para>
|
|
</important>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Automatic Character Set Conversion Between Server and Client</title>
|
|
|
|
<para>
|
|
<productname>PostgreSQL</productname> supports automatic
|
|
character set conversion between server and client for certain
|
|
character set combinations. The conversion information is stored in the
|
|
<literal>pg_conversion</> system catalog. <productname>PostgreSQL</>
|
|
comes with some predefined conversions, as shown in <xref
|
|
linkend="multibyte-translation-table">. You can create a new
|
|
conversion using the SQL command <command>CREATE CONVERSION</command>.
|
|
</para>
|
|
|
|
<table id="multibyte-translation-table">
|
|
<title>Client/Server Character Set Conversions</title>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Server Character Set</entry>
|
|
<entry>Available Client Character Sets</entry>
|
|
</row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>BIG5</literal></entry>
|
|
<entry><emphasis>not supported as a server encoding</emphasis>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>EUC_CN</literal></entry>
|
|
<entry><emphasis>EUC_CN</emphasis>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>EUC_JP</literal></entry>
|
|
<entry><emphasis>EUC_JP</emphasis>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>SJIS</literal>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>EUC_KR</literal></entry>
|
|
<entry><emphasis>EUC_KR</emphasis>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>EUC_TW</literal></entry>
|
|
<entry><emphasis>EUC_TW</emphasis>,
|
|
<literal>BIG5</literal>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>GB18030</literal></entry>
|
|
<entry><emphasis>not supported as a server encoding</emphasis>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>GBK</literal></entry>
|
|
<entry><emphasis>not supported as a server encoding</emphasis>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>ISO_8859_5</literal></entry>
|
|
<entry><emphasis>ISO_8859_5</emphasis>,
|
|
<literal>KOI8R</literal>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>,
|
|
<literal>WIN866</literal>,
|
|
<literal>WIN1251</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>ISO_8859_6</literal></entry>
|
|
<entry><emphasis>ISO_8859_6</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>ISO_8859_7</literal></entry>
|
|
<entry><emphasis>ISO_8859_7</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>ISO_8859_8</literal></entry>
|
|
<entry><emphasis>ISO_8859_8</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>JOHAB</literal></entry>
|
|
<entry><emphasis>JOHAB</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>KOI8R</literal></entry>
|
|
<entry><emphasis>KOI8R</emphasis>,
|
|
<literal>ISO_8859_5</literal>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>,
|
|
<literal>WIN866</literal>,
|
|
<literal>WIN1251</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>KOI8U</literal></entry>
|
|
<entry><emphasis>KOI8U</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN1</literal></entry>
|
|
<entry><emphasis>LATIN1</emphasis>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN2</literal></entry>
|
|
<entry><emphasis>LATIN2</emphasis>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>,
|
|
<literal>WIN1250</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN3</literal></entry>
|
|
<entry><emphasis>LATIN3</emphasis>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN4</literal></entry>
|
|
<entry><emphasis>LATIN4</emphasis>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN5</literal></entry>
|
|
<entry><emphasis>LATIN5</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN6</literal></entry>
|
|
<entry><emphasis>LATIN6</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN7</literal></entry>
|
|
<entry><emphasis>LATIN7</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN8</literal></entry>
|
|
<entry><emphasis>LATIN8</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN9</literal></entry>
|
|
<entry><emphasis>LATIN9</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>LATIN10</literal></entry>
|
|
<entry><emphasis>LATIN10</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>MULE_INTERNAL</literal></entry>
|
|
<entry><emphasis>MULE_INTERNAL</emphasis>,
|
|
<literal>BIG5</literal>,
|
|
<literal>EUC_CN</literal>,
|
|
<literal>EUC_JP</literal>,
|
|
<literal>EUC_KR</literal>,
|
|
<literal>EUC_TW</literal>,
|
|
<literal>ISO_8859_5</literal>,
|
|
<literal>KOI8R</literal>,
|
|
<literal>LATIN1</literal> to <literal>LATIN4</literal>,
|
|
<literal>SJIS</literal>,
|
|
<literal>WIN866</literal>,
|
|
<literal>WIN1250</literal>,
|
|
<literal>WIN1251</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>SJIS</literal></entry>
|
|
<entry><emphasis>not supported as a server encoding</emphasis>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>SQL_ASCII</literal></entry>
|
|
<entry><emphasis>any (no conversion will be performed)</emphasis>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>UHC</literal></entry>
|
|
<entry><emphasis>not supported as a server encoding</emphasis>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>UTF8</literal></entry>
|
|
<entry><emphasis>all supported encodings</emphasis>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN866</literal></entry>
|
|
<entry><emphasis>WIN866</emphasis>,
|
|
<literal>ISO_8859_5</literal>,
|
|
<literal>KOI8R</literal>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>,
|
|
<literal>WIN1251</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN874</literal></entry>
|
|
<entry><emphasis>WIN874</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1250</literal></entry>
|
|
<entry><emphasis>WIN1250</emphasis>,
|
|
<literal>LATIN2</literal>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1251</literal></entry>
|
|
<entry><emphasis>WIN1251</emphasis>,
|
|
<literal>ISO_8859_5</literal>,
|
|
<literal>KOI8R</literal>,
|
|
<literal>MULE_INTERNAL</literal>,
|
|
<literal>UTF8</literal>,
|
|
<literal>WIN866</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1252</literal></entry>
|
|
<entry><emphasis>WIN1252</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1253</literal></entry>
|
|
<entry><emphasis>WIN1253</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1254</literal></entry>
|
|
<entry><emphasis>WIN1254</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1255</literal></entry>
|
|
<entry><emphasis>WIN1255</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1256</literal></entry>
|
|
<entry><emphasis>WIN1256</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1257</literal></entry>
|
|
<entry><emphasis>WIN1257</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
<row>
|
|
<entry><literal>WIN1258</literal></entry>
|
|
<entry><emphasis>WIN1258</emphasis>,
|
|
<literal>UTF8</literal>
|
|
</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>
|
|
To enable automatic character set conversion, you have to
|
|
tell <productname>PostgreSQL</productname> the character set
|
|
(encoding) you would like to use in the client. There are several
|
|
ways to accomplish this:
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
Using the <command>\encoding</command> command in
|
|
<application>psql</application>.
|
|
<command>\encoding</command> allows you to change client
|
|
encoding on the fly. For
|
|
example, to change the encoding to <literal>SJIS</literal>, type:
|
|
|
|
<programlisting>
|
|
\encoding SJIS
|
|
</programlisting>
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
<application>libpq</> (<xref linkend="libpq-control">) has functions to control the client encoding.
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
Using <command>SET client_encoding TO</command>.
|
|
|
|
Setting the client encoding can be done with this SQL command:
|
|
|
|
<programlisting>
|
|
SET CLIENT_ENCODING TO '<replaceable>value</>';
|
|
</programlisting>
|
|
|
|
Also you can use the standard SQL syntax <literal>SET NAMES</literal>
|
|
for this purpose:
|
|
|
|
<programlisting>
|
|
SET NAMES '<replaceable>value</>';
|
|
</programlisting>
|
|
|
|
To query the current client encoding:
|
|
|
|
<programlisting>
|
|
SHOW client_encoding;
|
|
</programlisting>
|
|
|
|
To return to the default encoding:
|
|
|
|
<programlisting>
|
|
RESET client_encoding;
|
|
</programlisting>
|
|
</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>
|
|
Using <envar>PGCLIENTENCODING</envar>. If the environment variable
|
|
<envar>PGCLIENTENCODING</envar> is defined in the client's
|
|
environment, 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>
|
|
|
|
<listitem>
|
|
<para>
|
|
Using the configuration variable <xref
|
|
linkend="guc-client-encoding">. If the
|
|
<varname>client_encoding</> variable 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>
|
|
|
|
<para>
|
|
If the conversion of a particular character is not possible
|
|
— suppose you chose <literal>EUC_JP</literal> for the
|
|
server and <literal>LATIN1</literal> for the client, and some
|
|
Japanese characters are returned that do not have a representation in
|
|
<literal>LATIN1</literal> — an error is reported.
|
|
</para>
|
|
|
|
<para>
|
|
If the client character set is defined as <literal>SQL_ASCII</>,
|
|
encoding conversion is disabled, regardless of the server's character
|
|
set. Just as for the server, use of <literal>SQL_ASCII</> is unwise
|
|
unless you are working with all-ASCII data.
|
|
</para>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Further Reading</title>
|
|
|
|
<para>
|
|
These are good sources to start learning about various kinds of encoding
|
|
systems.
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><citetitle>CJKV Information Processing: Chinese, Japanese, Korean & Vietnamese Computing</citetitle></term>
|
|
|
|
<listitem>
|
|
<para>
|
|
Contains detailed explanations of <literal>EUC_JP</literal>,
|
|
<literal>EUC_CN</literal>, <literal>EUC_KR</literal>,
|
|
<literal>EUC_TW</literal>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><ulink url="http://www.unicode.org/"></ulink></term>
|
|
|
|
<listitem>
|
|
<para>
|
|
The web site of the Unicode Consortium.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>RFC 3629</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<acronym>UTF</acronym>-8 (8-bit UCS/Unicode Transformation
|
|
Format) is defined here.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</sect2>
|
|
|
|
</sect1>
|
|
|
|
</chapter>
|