<!-- $PostgreSQL: pgsql/doc/src/sgml/charset.sgml,v 2.65 2005/03/13 22:04:29 momjian Exp $ --> <chapter id="charset"> <title>Localization</> <para> This chapter describes the available localization features from the point of view of the administrator. <productname>PostgreSQL</productname> supports localization with two approaches: <itemizedlist> <listitem> <para> Using the locale features of the operating system to provide locale-specific collation order, number formatting, translated messages, and other aspects. </para> </listitem> <listitem> <para> Providing a number of different character sets defined in the <productname>PostgreSQL</productname> server, including multiple-byte character sets, to support storing text in all kinds of languages, and providing character set translation between client and server. </para> </listitem> </itemizedlist> </para> <sect1 id="locale"> <title>Locale Support</title> <indexterm zone="locale"><primary>locale</></> <para> <firstterm>Locale</> support refers to an application respecting cultural preferences regarding alphabets, sorting, number formatting, etc. <productname>PostgreSQL</> uses the standard ISO C and <acronym>POSIX</acronym> locale facilities provided by the server operating system. For additional information refer to the documentation of your system. </para> <sect2> <title>Overview</> <para> Locale support is automatically initialized when a database cluster is created using <command>initdb</command>. <command>initdb</command> 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 <command>initdb</command> exactly which locale to use by specifying the <option>--locale</option> option. For example: <screen> initdb --locale=sv_SE </screen> </para> <para> This example sets the locale to Swedish (<literal>sv</>) as spoken in Sweden (<literal>SE</>). Other possibilities might be <literal>en_US</> (U.S. English) and <literal>fr_CA</> (French Canadian). If more than one character set can be useful for a locale then the specifications look like this: <literal>cs_CZ.ISO8859-2</>. What locales are available under what names on your system depends on what was provided by the operating system vendor and what was installed. (On most systems, the command <literal>locale -a</> will provide a list of available locales.) </para> <para> Occasionally it is useful to mix rules from several locales, e.g., use English collation rules but Spanish messages. To support that, a set of locale subcategories exist that control only a certain aspect of the localization rules: <informaltable> <tgroup cols="2"> <tbody> <row> <entry><envar>LC_COLLATE</></> <entry>String sort order</> </row> <row> <entry><envar>LC_CTYPE</></> <entry>Character classification (What is a letter? Its upper-case equivalent?)</> </row> <row> <entry><envar>LC_MESSAGES</></> <entry>Language of messages</> </row> <row> <entry><envar>LC_MONETARY</></> <entry>Formatting of currency amounts</> </row> <row> <entry><envar>LC_NUMERIC</></> <entry>Formatting of numbers</> </row> <row> <entry><envar>LC_TIME</></> <entry>Formatting of dates and times</> </row> </tbody> </tgroup> </informaltable> The category names translate into names of <command>initdb</command> 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 <literal>initdb --locale=fr_CA --lc-monetary=en_US</literal>. </para> <para> If you want the system to behave as if it had no locale support, use the special locale <literal>C</> or <literal>POSIX</>. </para> <para> The nature of some locale categories is that their value has to be fixed for the lifetime of a database cluster. That is, once <command>initdb</command> has run, you cannot change them anymore. <literal>LC_COLLATE</literal> and <literal>LC_CTYPE</literal> are those categories. They affect the sort order of indexes, so they must be kept fixed, or indexes on text columns will become corrupt. <productname>PostgreSQL</productname> enforces this by recording the values of <envar>LC_COLLATE</> and <envar>LC_CTYPE</> that are seen by <command>initdb</>. The server automatically adopts those two values when it is started. </para> <para> The other locale categories can be changed as desired whenever the server is running by setting the run-time configuration variables that have the same name as the locale categories (see <xref linkend="runtime-config-client-format"> for details). The defaults that are chosen by <command>initdb</command> are actually only written into the configuration file <filename>postgresql.conf</filename> to serve as defaults when the server is started. If you delete the assignments from <filename>postgresql.conf</filename> then the server will inherit the settings from the execution environment. </para> <para> Note that the locale behavior of the server is determined by the environment variables seen by the server, not by the environment of any client. Therefore, be careful to configure the correct locale settings before starting the server. A consequence of this is that if client and server are set up in different locales, messages may appear in different languages depending on where they originated. </para> <note> <para> 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: <envar>LC_ALL</envar>, <envar>LC_COLLATE</envar> (the variable corresponding to the respective category), <envar>LANG</envar>. If none of these environment variables are set then the locale defaults to <literal>C</literal>. </para> <para> Some message localization libraries also look at the environment variable <envar>LANGUAGE</envar> 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 <application>gettext</>, for more information. </para> </note> <para> To enable messages to be translated to the user's preferred language, <acronym>NLS</acronym> must have been enabled at build time. This choice is independent of the other locale support. </para> </sect2> <sect2> <title>Behavior</> <para> Locale support influences the following features: <itemizedlist> <listitem> <para> Sort order in queries using <literal>ORDER BY</> <indexterm><primary>ORDER BY</><secondary>and locales</></indexterm> </para> </listitem> <listitem> <para> The ability to use indexes with <literal>LIKE</> clauses <indexterm><primary>LIKE</><secondary>and locales</></indexterm> </para> </listitem> <listitem> <para> The <function>to_char</> family of functions </para> </listitem> </itemizedlist> </para> <para> The drawback of using locales other than <literal>C</> or <literal>POSIX</> in <productname>PostgreSQL</> is its performance impact. It slows character handling and prevents ordinary indexes from being used by <literal>LIKE</>. For this reason use locales only if you actually need them. </para> </sect2> <sect2> <title>Problems</> <para> If locale support doesn't work in spite of the explanation above, check that the locale support in your operating system is correctly configured. To check what locales are installed on your system, you may use the command <literal>locale -a</literal> if your operating system provides it. </para> <para> Check that <productname>PostgreSQL</> is actually using the locale that you think it is. <envar>LC_COLLATE</> and <envar>LC_CTYPE</> settings are determined at <command>initdb</> time and cannot be changed without repeating <command>initdb</>. Other locale settings including <envar>LC_MESSAGES</> and <envar>LC_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 the <command>SHOW</> command. </para> <para> The directory <filename>src/test/locale</> in the source distribution contains a test suite for <productname>PostgreSQL</>'s locale support. </para> <para> 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. </para> <para> Maintaining catalogs of message translations requires the on-going efforts of many volunteers that want to see <productname>PostgreSQL</> 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 <xref linkend="nls"> or write to the developers' mailing list. </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, including single-byte character sets such as the ISO 8859 series and multiple-byte character sets such as <acronym>EUC</> (Extended Unix Code), UTF8, and Mule internal code. All character sets can be used transparently throughout the server. (If you use extension functions from other sources, it depends on whether they wrote their code correctly.) 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 using <command>createdb</command> or by using the SQL command <command>CREATE DATABASE</>. So you can have multiple databases each with a different character set. </para> <sect2 id="multibyte-charset-supported"> <title>Supported Character Sets</title> <para> <xref linkend="charset-table"> shows the character sets available for use in the server. </para> <table id="charset-table"> <title>Server Character Sets</title> <tgroup cols="2"> <thead> <row> <entry>Name</entry> <entry>Description</entry> <entry>Language</entry> <entry>Aliases</entry> </row> </thead> <tbody> <row> <entry><literal>BIG5</literal></entry> <entry>Big Five</entry> <entry>Traditional Chinese</entry> <entry>WIN950, Windows950</entry> </row> <row> <entry><literal>EUC_CN</literal></entry> <entry>Extended UNIX Code-CN</entry> <entry>Simplified Chinese</entry> <entry></entry> </row> <row> <entry><literal>EUC_JP</literal></entry> <entry>Extended UNIX Code-JP</entry> <entry>Japanese</entry> <entry></entry> </row> <row> <entry><literal>EUC_KR</literal></entry> <entry>Extended UNIX Code-KR</entry> <entry>Korean</entry> <entry></entry> </row> <row> <entry><literal>EUC_TW</literal></entry> <entry>Extended UNIX Code-TW</entry> <entry>Traditional Chinese, Taiwanese</entry> <entry></entry> </row> <row> <entry><literal>GB18030</literal></entry> <entry>National Standard</entry> <entry>Chinese</entry> <entry></entry> </row> <row> <entry><literal>GBK</literal></entry> <entry>Extended National Standard</entry> <entry>Simplified Chinese</entry> <entry>WIN936, Windows936</entry> </row> <row> <entry><literal>ISO_8859_5</literal></entry> <entry>ISO 8859-5, <acronym>ECMA</> 113</entry> <entry>Latin/Cyrillic</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></entry> </row> <row> <entry><literal>ISO_8859_7</literal></entry> <entry>ISO 8859-7, <acronym>ECMA</> 118</entry> <entry>Latin/Greek</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></entry> </row> <row> <entry><literal>JOHAB</literal></entry> <entry><acronym>JOHAB</></entry> <entry>Korean (Hangul)</entry> <entry></entry> </row> <row> <entry><literal>KOI8</literal></entry> <entry><acronym>KOI</acronym>8-R(U)</entry> <entry>Cyrillic</entry> <entry>KOI8R</entry> </row> <row> <entry><literal>LATIN1</literal></entry> <entry>ISO 8859-1, <acronym>ECMA</> 94</entry> <entry>Western European</entry> <entry>ISO88591</entry> </row> <row> <entry><literal>LATIN2</literal></entry> <entry>ISO 8859-2, <acronym>ECMA</> 94</entry> <entry>Central European</entry> <entry>ISO88592</entry> </row> <row> <entry><literal>LATIN3</literal></entry> <entry>ISO 8859-3, <acronym>ECMA</> 94</entry> <entry>South European</entry> <entry>ISO88593</entry> </row> <row> <entry><literal>LATIN4</literal></entry> <entry>ISO 8859-4, <acronym>ECMA</> 94</entry> <entry>North European</entry> <entry>ISO88594</entry> </row> <row> <entry><literal>LATIN5</literal></entry> <entry>ISO 8859-9, <acronym>ECMA</> 128</entry> <entry>Turkish</entry> <entry>ISO88599</entry> </row> <row> <entry><literal>LATIN6</literal></entry> <entry>ISO 8859-10, <acronym>ECMA</> 144</entry> <entry>Nordic</entry> <entry>ISO885910</entry> </row> <row> <entry><literal>LATIN7</literal></entry> <entry>ISO 8859-13</entry> <entry>Baltic</entry> <entry>ISO885913</entry> </row> <row> <entry><literal>LATIN8</literal></entry> <entry>ISO 8859-14</entry> <entry>Celtic</entry> <entry>ISO885914</entry> </row> <row> <entry><literal>LATIN9</literal></entry> <entry>ISO 8859-15</entry> <entry>LATIN1 with Euro and accents</entry> <entry>ISO885915</entry> </row> <row> <entry><literal>LATIN10</literal></entry> <entry>ISO 8859-16, <acronym>ASRO</> SR 14111</entry> <entry>Romanian</entry> <entry>ISO885916</entry> </row> <row> <entry><literal>MULE_INTERNAL</literal></entry> <entry>Mule internal code</entry> <entry>Multi-lingual Emacs</entry> <entry></entry> </row> <row> <entry><literal>SJIS</literal></entry> <entry>Shift JIS</entry> <entry>Japanese</entry> <entry>Mskanji, ShiftJIS, WIN932, Windows932</entry> </row> <row> <entry><literal>SQL_ASCII</literal></entry> <entry><acronym>ASCII</acronym></entry> <entry>English</entry> <entry></entry> </row> <row> <entry><literal>UHC</literal></entry> <entry>Unified Hangul Code</entry> <entry>Korean</entry> <entry>WIN949, Windows949</entry> </row> <row> <entry><literal>UTF8</literal></entry> <entry>Unicode, 8-bit</entry> <entry><emphasis>all</></entry> <entry>Unicode</entry> </row> <row> <entry><literal>WIN866</literal></entry> <entry>Windows CP866</entry> <entry>Cyrillic</entry> <entry>ALT</entry> </row> <row> <entry><literal>WIN874</literal></entry> <entry>Windows CP874</entry> <entry>Thai</entry> <entry></entry> </row> <row> <entry><literal>WIN1250</literal></entry> <entry>Windows CP1250</entry> <entry>Central European</entry> <entry></entry> </row> <row> <entry><literal>WIN1251</literal></entry> <entry>Windows CP1251</entry> <entry>Cyrillic</entry> <entry>WIN</entry> </row> <row> <entry><literal>WIN1256</literal></entry> <entry>Windows CP1256</entry> <entry>Arabic</entry> <entry></entry> </row> <row> <entry><literal>WIN1258</literal></entry> <entry>Windows CP1258</entry> <entry>Vietnamese</entry> <entry>ABC, TCVN, TCVN5712, VSCII</entry> </row> </tbody> </tgroup> </table> <para> Not all <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> </sect2> <sect2> <title>Setting the Character Set</title> <para> <command>initdb</> defines the default character set for a <productname>PostgreSQL</productname> cluster. For example, <screen> initdb -E EUC_JP </screen> sets the default character set (encoding) to <literal>EUC_JP</literal> (Extended Unix Code for Japanese). You can use <option>--encoding</option> instead of <option>-E</option> if you prefer to type longer option strings. If no <option>-E</> or <option>--encoding</option> option is given, <literal>SQL_ASCII</> is used. </para> <para> You can create a database with a different character set: <screen> createdb -E EUC_KR korean </screen> This will create a database named <literal>korean</literal> that uses the character set <literal>EUC_KR</literal>. Another way to accomplish this is to use this SQL command: <programlisting> CREATE DATABASE korean WITH ENCODING 'EUC_KR'; </programlisting> The encoding for a database is stored in the system catalog <literal>pg_database</literal>. You can see that by using the <option>-l</option> option or the <command>\l</command> command of <command>psql</command>. <screen> $ <userinput>psql -l</userinput> List of databases Database | Owner | Encoding ---------------+---------+--------------- euc_cn | t-ishii | EUC_CN euc_jp | t-ishii | EUC_JP euc_kr | t-ishii | EUC_KR euc_tw | t-ishii | EUC_TW mule_internal | t-ishii | MULE_INTERNAL regression | t-ishii | SQL_ASCII template1 | t-ishii | EUC_JP test | t-ishii | EUC_JP utf8 | t-ishii | UTF8 (9 rows) </screen> </para> <important> <para> Although you can specify any encoding you want for a database, it is unwise to choose an encoding that is not what is expected by the locale you have selected. The <literal>LC_COLLATE</literal> and <literal>LC_CTYPE</literal> settings imply a particular encoding, and locale-dependent operations (such as sorting) are likely to misinterpret data that is in an incompatible encoding. </para> <para> Since these locale settings are frozen by <command>initdb</>, the apparent flexibility to use different encodings in different databases of a cluster is more theoretical than real. It is likely that these mechanisms will be revisited in future versions of <productname>PostgreSQL</productname>. </para> <para> One way to use multiple encodings safely is to set the locale to <literal>C</> or <literal>POSIX</> during <command>initdb</>, thus disabling any real locale awareness. </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 sets. The conversion information is stored in the <literal>pg_conversion</> system catalog. You can create a new conversion by using the SQL command <command>CREATE CONVERSION</command>. <productname>PostgreSQL</> comes with some predefined conversions. They are listed in <xref linkend="multibyte-translation-table">. </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>BIG5</emphasis>, <literal>EUC_TW</literal> <literal>MULE_INTERNAL</literal>, <literal>UTF8</literal> </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>GB18030</emphasis>, <literal>UTF8</literal> </entry> </row> <row> <entry><literal>GBK</literal></entry> <entry><emphasis>GBK</emphasis>, <literal>UTF8</literal> </entry> </row> <row> <entry><literal>ISO_8859_5</literal></entry> <entry><emphasis>ISO_8859_5</emphasis>, <literal>KOI8</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>KOI8</literal></entry> <entry><emphasis>KOI8</emphasis>, <literal>ISO_8859_5</literal>, <literal>MULE_INTERNAL</literal>, <literal>UTF8</literal>, <literal>WIN866</literal>, <literal>WIN1251</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>KOI8</literal>, <literal>LATIN1</literal> to <literal>LATIN4</literal>, <literal>LATIN2</literal>, <literal>LATIN3</literal>, <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>SJIS</emphasis>, <literal>EUC_JP</literal>, <literal>MULE_INTERNAL</literal>, <literal>UTF8</literal> </entry> </row> <row> <entry><literal>SQL_ASCII</literal></entry> <entry><emphasis>SQL_ASCII</emphasis>, <literal>MULE_INTERNAL</literal>, <literal>UTF8</literal> </entry> </row> <row> <entry><literal>UHC</literal></entry> <entry><emphasis>UHC</emphasis>, <literal>UTF8</literal> </entry> </row> <row> <entry><literal>UTF8</literal></entry> <entry><emphasis>UTF8</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>ISO_8859_6</literal>, <literal>ISO_8859_7</literal>, <literal>ISO_8859_8</literal>, <literal>GB18030</literal>, <literal>GBK</literal>, <literal>JOHAB</literal>, <literal>KOI8</literal>, <literal>LATIN1</literal> to <literal>LATIN10</literal>, <literal>SJIS</literal>, <literal>UHC</literal>, <literal>WIN866</literal>, <literal>WIN874</literal>, <literal>WIN1250</literal>, <literal>WIN1251</literal>, <literal>WIN1256</literal>, <literal>WIN1258</literal> </entry> </row> <row> <entry><literal>WIN866</literal></entry> <entry><emphasis>WIN866</emphasis>, <literal>ISO_8859_5</literal>, <literal>KOI8</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>KOI8</literal>, <literal>MULE_INTERNAL</literal>, <literal>UTF8</literal>, <literal>WIN866</literal> </entry> </row> <row> <entry><literal>WIN1256</literal></entry> <entry><emphasis>WIN1256</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 the 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> Using <application>libpq</> functions. <command>\encoding</command> actually calls <function>PQsetClientEncoding()</function> for its purpose. <synopsis> int PQsetClientEncoding(PGconn *<replaceable>conn</replaceable>, const char *<replaceable>encoding</replaceable>); </synopsis> where <replaceable>conn</replaceable> is a connection to the server, and <replaceable>encoding</replaceable> is the encoding you want to use. If the function successfully sets the encoding, it returns 0, otherwise -1. The current encoding for this connection can be determined by using: <synopsis> int PQclientEncoding(const PGconn *<replaceable>conn</replaceable>); </synopsis> Note that it returns the encoding ID, not a symbolic string such as <literal>EUC_JP</literal>. To convert an encoding ID to an encoding name, you can use: <synopsis> char *pg_encoding_to_char(int <replaceable>encoding_id</replaceable>); </synopsis> </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 more 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, then some Japanese characters cannot be converted to <literal>LATIN1</literal> — it is transformed to its hexadecimal byte values in parentheses, e.g., <literal>(826C)</literal>. </para> </sect2> <sect2> <title>Further Reading</title> <para> These are good sources to start learning about various kinds of encoding systems. <variablelist> <varlistentry> <term><ulink url="http://www.i18ngurus.com/docs/984813247.html"></ulink></term> <listitem> <para> An extensive collection of documents about character sets, encodings, and code pages. </para> </listitem> </varlistentry> <variablelist> <varlistentry> <term><ulink url="ftp://ftp.ora.com/pub/examples/nutshell/ujip/doc/cjk.inf"></ulink></term> <listitem> <para> Detailed explanations of <literal>EUC_JP</literal>, <literal>EUC_CN</literal>, <literal>EUC_KR</literal>, <literal>EUC_TW</literal> appear in section 3.2. </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 2044</term> <listitem> <para> <acronym>UTF</acronym>-8 is defined here. </para> </listitem> </varlistentry> </variablelist> </para> </sect2> </sect1> </chapter> <!-- Keep this comment at the end of the file Local variables: mode:sgml sgml-omittag:nil sgml-shorttag:t sgml-minimize-attributes:nil sgml-always-quote-attributes:t sgml-indent-step:1 sgml-indent-data:t sgml-parent-document:nil sgml-default-dtd-file:"./reference.ced" sgml-exposed-tags:nil sgml-local-catalogs:("/usr/lib/sgml/catalog") sgml-local-ecat-files:nil End: -->