--- /dev/null
+
+ PostgreSQL Charsets README
+ Draft v0.1, Tue Jul 20 15:49:07 CEST 1999
+
+ This document is a brief overview of the national charsets support
+ that PostgreSQL ver. 6.5 has implemented. Various compilation options
+ and setup tips are mentioned here to be helpful in the particular use.
+
+ ---------------------------------------------------------------------------
+
+ Table of Contents
+
+ 1. Locale awareness
+
+ 2. Single-byte charsets recoding
+
+ 3. Multi-byte support/recoding
+
+ 4. Credits
+
+ ---------------------------------------------------------------------------
+
+ 1. Locale awareness
+
+ PostgreSQL server supports both locale aware and locale not aware
+ (default) operational modes. You can determine this mode during the
+ configuration stage of the installation with --enable-locale option.
+
+ If you don't use --enable-locale, the multi-language code will not be
+ compiled and PostgreSQL will behave as an ASCII compliant application.
+ This mode is useful for its speed but only provided that you don't
+ have to consider national specific chars.
+
+ With --enable-locale you will get a locale aware server using LC_*
+ environment variables to determine how to process national specifics.
+ In this case strcoll(3) and similar functions are used internally
+ so speed is somewhat lower.
+
+ Notice here that --enable-locale is sufficient when all your clients
+ use the same single-byte encoding as the database server does.
+
+ When your clients use encoding different from the server than you have
+ to use, moreover, --enable-recode or --with-mb=<encoding> options on
+ the server side or a particular client that does recoding itself (e.g.
+ there exists a PostgreSQL ODBC driver for Win32 with various Cyrillic
+ encoding capability). Option --with-mb=<encoding> is necessary for the
+ multi-byte charsets support.
+
+
+ 2. Single-byte charsets recoding
+
+ You can set up this feature with --enable-recode option. This option
+ is described as 'enable Cyrillic recode support' which doesn't express
+ all its power. It can be used for *any* single-byte charset recoding.
+
+ This method uses charset.conf file located in the $PGDATA directory.
+ It's a typical configuration text file where spaces and newlines
+ separate items and records and # specifies comments. Three keywords
+ with the following syntax are recognized here:
+
+ BaseCharset <server_charset>
+ RecodeTable <from_charset> <to_charset> <file_name>
+ HostCharset <host_spec> <host_charset>
+
+ BaseCharset defines encoding of the database server. All charset
+ names are only used for mapping inside the charset.conf so you can
+ freely use typing-friendly names.
+
+ RecodeTable records specify translation table between server and client.
+ The file name is relative to the $PGDATA directory. Table file format
+ is very simple. There are no keywords and characters are represented by
+ a pair of decimal or hexadecimal (0x prefixed) values on single lines:
+
+ <char_value> <translated_char_value>
+
+ HostCharset records define IP address and charset. You can use a single
+ IP address, an IP mask range starting from the given address or an IP
+ interval (e.g. 127.0.0.1, 192.168.1.100/24, 192.168.1.20-192.168.1.40)
+
+ The charset.conf is always processed up to the end, so you can easily
+ specify exceptions from the previous rules. In the src/data you will
+ find charset.conf example and a few recoding tables.
+
+ As this solution is based on the client's IP address / charset mapping
+ there are obviously some restrictions as well. You can't use different
+ encoding on the same host at the same time. It's also inconvenient when
+ you boot your client hosts into more operating systems.
+ Nevertheless, when these restrictions are not limiting and you don't
+ need multi-byte chars than it's a simple and effective solution.
+
+
+ 3. Multi-byte support/recoding
+
+ It's a new generation of charset encoding in PostgreSQL designed as a
+ more complex solution supporting both single-byte and multi-byte chars.
+ You can set up this feature with --with-mb=<encoding> option.
+
+ There is no IP mapping file and recoding is controlled through the new
+ SQL statements. Recoding tables are included in the code. Many national
+ charsets are already supported and further will follow.
+
+ See doc/README.mb, doc/README.mb.jp to get detailed instruction on how
+ to use the multibyte support. In the file doc/README.locale there is
+ a particular instruction on usage of the multibyte support with Cyrillic.
+
+
+ 4. Credits
+
+ I'd like to thank the PostgreSQL development team and all contributors
+ for creating PostgreSQL. Thanks to Oleg Bartunov, Oleg Broytmann and
+ Tatsuo Ishii for opening the door into the multi-language world.
+