PostgreSQL 7.0 multi-byte (MB) support README Mar 22 2000 Tatsuo Ishii ishii@postgresql.org http://www.sra.co.jp/people/t-ishii/PostgreSQL/ 0. Introduction The MB support is intended for allowing PostgreSQL to handle multi-byte character sets such as EUC(Extended Unix Code), Unicode and Mule internal code. With the MB enabled you can use multi-byte character sets in regexp ,LIKE and some other functions. The default encoding system chosen is determined while initializing your PostgreSQL installation using initdb(1). Note that this can be overridden when you create a database using createdb(1) or by using a create database SQL command. So you could have multiple databases with each different encoding system. MB also fixes some problems concerning with 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) 1. How to use run configure with a multibyte option: % ./configure --enable-multibyte[=encoding_system] where the encoding_system is one of: 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 Example: % ./configure --enable-multibyte=EUC_JP If the encoding system is omitted (./configure --enable-multibyte), SQL_ASCII is assumed. 2. How to set the encoding initdb command defines the default encoding for a PostgreSQL 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 like longer option string:-) 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 "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) 3. Automatic encoding translation between backend and frontend PostgreSQL supports an automatic encoding translation between backend and frontend for some encodings. encoding of backend available encoding of frontend -------------------------------------------------------------------- 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 PostgreSQL the encoding you would like to use in frontend. There are several ways to accomplish this. o using \encoding command in psql \encoding allows you to change frontend encoding on the fly. For example, to change the encoding to SJIS, type: \encoding SJIS o using libpq functions \encoding actually calls PQsetClientEncoding() for its purpose. int PQsetClientEncoding(PGconn *conn, const char *encoding) 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) o using PGCLIENTENCODING If an environment variable PGCLIENTENCODING is defined in the frontend, an automatic encoding translation is done by the backend. o using SET CLIENT_ENCODING TO command 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; 4. About Unicode An automatic encoding translation between Unicode and any other encodings is not supported (yet). 5. 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) 6. 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. 5. History 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 Appendix: [Here is a good documentation explaining how to use WIN1250 on Windows/ODBC from Pavel Behal. Please note that Installation step 1) is not necceary in 6.5.1 -- Tatsuo] Version: 0.91 for PgSQL 6.5 Author: Pavel Behal Revised by: Tatsuo Ishii Email: behal@opf.slu.cz Licence: The Same as PostgreSQL Sorry for my Eglish and C code, I'm not native :-) !!!!!!!!!!!!!!!!!!!!!!!!! NO WARRANTY !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Instalation: ------------ 1) Change three affected files in source directories (I don't have time to create proper patch diffs, I don't know how) 2) Compile with enabled locale and multibyte set to LATIN2 3) Setup properly your instalation, do not forget to create locale variables in your profile (environment). Ex. (may not be exactly true): 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 4) You have to start the postmaster with locales set! 5) Try it with Czech language, it have to sort 5) Install ODBC driver for PgSQL into your M$ Windows 6) Setup properly your data source. Include this line in your ODBC configuration dialog in field "Connect Settings:" : SET CLIENT_ENCODING = 'WIN1250'; 7) Now try it again, but in Windows with ODBC. Description: ------------ - Depends on proper system locales, tested with RH6.0 and Slackware 3.6, with cs_CZ.iso8859-2 loacle - Never try to set-up server multibyte database encoding to WIN1250, always use LATIN2 instead. There is not WIN1250 locale in Unix - WIN1250 encoding is useable only for M$W ODBC clients. The characters are on thy fly re-coded, to be displayed and stored back properly Important: ---------- - it reorders your sort order depending on your LC_... setting, so don't be confused with regression tests, they don't use locale - "ch" is corectly sorted only in some newer locales (Ex. RH6.0) - you have to insert money as '162,50' (with comma in aphostrophes!) - not tested properly