+ url="http://www.sra.co.jp/people/t-ishii/PostgreSQL/">Tatsuo's
+ web site for more information.
+
+
+
+ Multi-byte (
MB) support is intended to allow
+ multiple-byte character sets such as EUC (Extended Unix Code), Unicode and
+ Mule internal code. With
MB enabled you can use multi-byte
+ character sets in regular expressions (regexp), LIKE, and some
+ other functions. The default
+ encoding system is selected while initializing your
+
Postgres installation using
+
initdb. Note that this can be
+ overridden when you create a database using
+
createdb or by using the SQL command
+ CREATE DATABASE. So you can have multiple databases each with
+ a different encoding system.
+
+
+
MB also fixes some problems concerning 8-bit single byte
+ character sets including ISO8859. (I would not say all of problems
+ have been fixed. I just confirmed that the regression test ran fine
+ and a few French characters could be used with the patch. Please let
+ me know if you find any problem while using 8-bit characters.)
+
+
+
+
Enabling MB
+
+ Run configure with a multibyte option:
+
+% ./configure --enable-multibyte[=encoding_system]
+
+
+ where encoding_system can be one of the
+ values in the following table:
+
+
<productname>Postgres</productname> Character Set Encodings
+ Encodings
+
+
+ |
+ Encoding
+ Description
+
+
+
+ |
+ SQL_ASCII
+ ASCII
+
+ |
+ EUC_JP
+ Japanese EUC
+
+ |
+ EUC_CN
+ Chinese EUC
+
+ |
+ EUC_KR
+ Korean EUC
+
+ |
+ EUC_TW
+ Taiwan EUC
+
+ |
+ UNICODE
+ Unicode(UTF-8)
+
+ |
+ MULE_INTERNAL
+ Mule internal
+
+ |
+ LATIN1
+ ISO 8859-1 English and some European languages
+
+ |
+ LATIN2
+ ISO 8859-2 English and some European languages
+
+ |
+ LATIN3
+ ISO 8859-3 English and some European languages
+
+ |
+ LATIN4
+ ISO 8859-4 English and some European languages
+
+ |
+ LATIN5
+ ISO 8859-5 English and some European languages
+
+ |
+ KOI8
+ KOI8-R
+
+ |
+ WIN
+ Windows CP1251
+
+ |
+ ALT
+ Windows CP866
+
+
+
+
+
+
+ Here is an example of configuring
+
Postgres to use a Japanese encoding by
+ default:
+
+% ./configure --enable-multibyte=EUC_JP
+
+
+
+ If the encoding system is omitted (./configure --enable-multibyte),
+ SQL_ASCII is assumed.
+
+
+
+
+
Setting the Encoding
+
+
initdb defines the default encoding
+ for a
Postgres installation. For example:
+
+% initdb -E EUC_JP
+
+
+ sets the default encoding to EUC_JP(Extended Unix Code for Japanese).
+ Note that you can use "--encoding" instead of "-E" if you prefer
+ to type longer option strings.
+ If no -E or --encoding option is given, the encoding
+ specified at the compile time is used.
+
+
+ You can create a database with a different encoding:
+
+% createdb -E EUC_KR korean
+
+
+ will create a database named "korean" with EUC_KR encoding. The
+ another way to accomplish this is to use a SQL command:
+
+CREATE DATABASE korean WITH ENCODING = 'EUC_KR';
+
+
+ The encoding for a database is represented as an
+ encoding column in the
+ pg_database system catalog.
+ You can see that by using -l or \l of psql
+ command.
+
+$ psql -l
+ 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
+ unicode | t-ishii | UNICODE
+(9 rows)
+
+
+
+
+
+
Automatic encoding translation between backend and</div>
<div class="diff add">+ frontend
+
+
Postgres supports an automatic
+ encoding translation between backend
+ and frontend for some encodings.
+
+
<productname>Postgres</productname> Client/Server Character Set Encodings
+ Communication Encodings
+
+
+ |
+ Server Encoding
+ Available Client Encodings
+
+
+
+ |
+ EUC_JP
+ EUC_JP, SJIS
+
+ |
+ EUC_TW
+ EUC_TW, BIG5
+
+
+ LATIN2
+ LATIN2, WIN1250
+
+ |
+ LATIN5
+ LATIN5, WIN, ALT
+
+ |
+ MULE_INTERNAL
+ EUC_JP, SJIS, EUC_KR, EUC_CN,
+ EUC_TW, BIG5, LATIN1 to LATIN5,
+ WIN, ALT, WIN1250
+
+
+
+
+
+
+ To enable the automatic encoding translation, you have to tell
+
Postgres the encoding you would like
+ to use in frontend. There are
+ several ways to accomplish this.
+
+
+
+ Using the \encoding command in
+ \encoding allows you to change frontend
+ encoding on the fly. For
+ example, to change the encoding to SJIS, type:
+
+\encoding SJIS
+
+
+
+
+
+ Using libpq functions.
+ \encoding actually calls
+ PQsetClientEncoding() for its purpose.
+
+int PQsetClientEncoding(PGconn *conn, const char *encoding)
+
+
+ where conn is a connection to the backend,
+ and encoding is an encoding you
+ want to use. If it successfully sets the encoding, it returns 0,
+ otherwise -1. The current encoding for this connection can be shown by
+ using:
+
+int PQclientEncoding(const PGconn *conn)
+
+
+ Note that it returns the "encoding id," not the encoding symbol string
+ such as "EUC_JP." To convert an encoding id to an encoding symbol, you
+ can use:
+
+char *pg_encoding_to_char(int encoding_id)
+
+
+
+
+
+ Using PGCLIENTENCODING.
+
+ If an environment variable PGCLIENTENCODING is defined in the
+ frontend, an automatic encoding translation is done by the backend.
+
+
+
+
+ Using SET CLIENT_ENCODING TO.
+
+ Setting the frontend side encoding can be done a SQL command:
+
+SET CLIENT_ENCODING TO 'encoding';
+
+
+ Also you can use SQL92 syntax "SET NAMES" for this purpose:
+
+SET NAMES 'encoding';
+
+
+ To query the current the frontend encoding:
+
+SHOW CLIENT_ENCODING;
+
+
+ To return to the default encoding:
+
+RESET CLIENT_ENCODING;
+
+
+
+
+
+
+
+
+
About Unicode
+
+ An automatic encoding translation between Unicode and other
+ encodings is not yet supported.
+
+
+
+
+
What happens if the translation is not possible?
+
+ Suppose you choose EUC_JP for the backend, LATIN1 for the frontend,
+ then some Japanese characters could not be translated into LATIN1. In
+ this case, a letter cannot be represented in the LATIN1 character set,
+ would be transformed as:
+
+(HEXA DECIMAL)
+
+
+
+
+
+
References
+
+ These are good sources to start learning various kind of encoding
+ systems.
+
+
+
+ ftp://ftp.ora.com/pub/examples/nutshell/ujip/doc/cjk.inf
+ Detailed explanations of EUC_JP, EUC_CN, EUC_KR, EUC_TW
+ appear in section 3.2.
+
+
+
+
+ Unicode:
http://www.unicode.org/+ The homepage of UNICODE.
+
+
+
+
+ RFC 2044
+ UTF-8 is defined here.
+
+
+
+
+
+
+
+
History
+
+May 20, 2000
+ * SJIS UDC (NEC selection IBM kanji) support contributed
+ by Eiji Tokuya
+ * Changes above will appear in 7.0.1
+
+Mar 22, 2000
+ * Add new libpq functions PQsetClientEncoding, PQclientEncoding
+ * ./configure --with-mb=EUC_JP
+ now deprecated. use
+ ./configure --enable-multibyte=EUC_JP
+ instead
+ * Add SQL_ASCII regression test case
+ * Add SJIS User Defined Character (UDC) support
+ * All of above will appear in 7.0
+
+July 11, 1999
+ * Add support for WIN1250 (Windows Czech) as a client encoding
+ (contributed by Pavel Behal)
+ * fix some compiler warnings (contributed by Tomoaki Nishiyama)
+
+Mar 23, 1999
+ * Add support for KOI8(KOI8-R), WIN(CP1251), ALT(CP866)
+ (thanks Oleg Broytmann for testing)
+ * Fix problem with MB and locale
+
+Jan 26, 1999
+ * Add support for Big5 for fronend encoding
+ (you need to create a database with EUC_TW to use Big5)
+ * Add regression test case for EUC_TW
+ (contributed by
Jonah Kuo)+
+Dec 15, 1998
+ * Bugs related to SQL_ASCII support fixed
+
+Nov 5, 1998
+ * 6.4 release. In this version, pg_database has "encoding"
+ column that represents the database encoding
+
+Jul 22, 1998
+ * determine encoding at initdb/createdb rather than compile time
+ * support for PGCLIENTENCODING when issuing COPY command
+ * support for SQL92 syntax "SET NAMES"
+ * support for LATIN2-5
+ * add UNICODE regression test case
+ * new test suite for MB
+ * clean up source files
+
+Jun 5, 1998
+ * add support for the encoding translation between the backend
+ and the frontend
+ * new command SET CLIENT_ENCODING etc. added
+ * add support for LATIN1 character set
+ * enhance 8 bit cleaness
+
+April 21, 1998 some enhancements/fixes
+ * character_length(), position(), substring() are now aware of
+ multi-byte characters
+ * add octet_length()
+ * add --with-mb option to configure
+ * new regression tests for EUC_KR
+ (contributed by
Soonmyung. Hong)+ * add some test cases to the EUC_JP regression test
+ * fix problem in regress/regress.sh in case of System V
+ * fix toupper(), tolower() to handle 8bit chars
+
+Mar 25, 1998 MB PL2 is incorporated into PostgreSQL 6.3.1
+
+Mar 10, 1998 PL2 released
+ * add regression test for EUC_JP, EUC_CN and MULE_INTERNAL
+ * add an English document (this file)
+ * fix problems concerning 8-bit single byte characters
+
+Mar 1, 1998 PL1 released
+
+
+
+
+
+
WIN1250 on Windows/ODBC
+
+
+
+ The WIN1250 character set on Windows client platforms can be used
+ with
Postgres with locale support
+ enabled.
+
+
+ The following should be kept in mind:
+
+
+
+ Success depends on proper system locales. This has been tested
+ with RH6.0 and Slackware 3.6, with cs_CZ.iso8859-2 locale.
+
+
+
+
+ Never try to set the server multibyte database encoding to WIN1250.
+ Always use LATIN2 instead since there is not a WIN1250 locale
+ in Unix.
+
+
+
+
+ WIN1250 encoding is useable only for M$W ODBC clients. The
+ characters are recoded on the fly, to be displayed and stored
+ back properly.
+
+
+
+
+
+ When running, it is important to remember the following:
+
+
+
+ This configuration reorders your sort order depending on your
+ LC_x settings. Don't be
+ confused with the regression test results since they don't use
+ locale.
+
+
+
+
+ A locale such as "ch" is correctly sorted
+ only if your system
+ supports that locale; older systems may not do so but new ones
+ (e.g. RH6.0) do.
+
+
+
+
+ You have to insert money as '162,50' (note
+ comma within the single-quotes).
+
+
+
+
+ At the time of writing (early 1999), this configuration has
+ not received extensive testing. Please let us know of any
+ changes you had to make!
+
+
+
+
+
+
WIN1250 on Windows/ODBC
+
+ Change the three relevant files in the source directories.
+
+
+
+
+ Compile
Postgres with local enabled
+ and the multibyte encoding set to LATIN2.
+
+
+
+
+ Set up your instalation. Do not forget to create locale
+ variables in your profile (environment). For example (this may
+ not be correct for your environment):
+
+LC_ALL=cs_CZ.ISO8859-2
+LC_COLLATE=cs_CZ.ISO8859-2
+LC_CTYPE=cs_CZ.ISO8859-2
+LC_MONETARY=cs_CZ.ISO8859-2
+LC_NUMERIC=cs_CZ.ISO8859-2
+LC_TIME=cs_CZ.ISO8859-2
+
+
+
+
+
+ You have to start the postmaster with locales set!
+
+
+
+
+ Try it with Czech language, and have it sort on a query.
+
+
+
+
+ Install ODBC driver for PgSQL on your M$ Windows machine.
+
+
+
+
+ Setup properly your data source. Include this line in your ODBC
+ configuration dialog in the field Connect Settings:
+
+SET CLIENT_ENCODING = 'WIN1250';
+
+
+
+
+
+ Now try it again, but in Windows with ODBC.
+
+
+
+
+
+
+
+
projects / postgresql.git / commitdiff