mysqld can issue error messages in the following languages: Czech,
Dutch, English (the default), French, German, Hungarian, Italian, Norwegian,
Norwegian-ny, Polish, Portuguese, Spanish and Swedish.
To start mysqld with a particular language, use either the
--language=lang or -L lang options. For example:
shell> mysqld --language=swedish
or:
shell> mysqld --language=/usr/local/share/swedish
Note that all language names are specified in lowercase.
The language files are located (by default) in `mysql_base_dir/share/LANGUAGE/'.
To update the error message file, you should edit the `errmsg.txt' file and execute the following command to generate the `errmsg.sys' file:
shell> comp_err errmsg.txt errmsg.sys
If you upgrade to a newer version of MySQL, remember to repeat your changes with the new `errmsg.txt' file.
By default, MySQL uses the ISO-8859-1 (Latin1) character set. This is the character set used in the USA and western Europe.
The character set determines what characters are allowed in names and how
things are sorted by the ORDER BY and GROUP BY clauses of
the SELECT statement.
You can change the character set at compile time by using the
--with-charset=charset option to configure.
See section 4.7.1 Quick installation overview.
To add another character set to MySQL, use the following procedure:
MYSET below.
ctype_MYSET, to_lower_MYSET and so on.
to_lower[] and to_upper[] are simple arrays that hold the
lowercase and uppercase characters corresponding to each member of the
character set. For example:
to_lower['A'] should contain 'a' to_upper['a'] should contain 'A'
sort_order[] is a map indicating how characters should be ordered for
comparison and sorting purposes. For many character sets, this is the same as
to_upper[] (which means sorting will be case insensitive).
MySQL will sort characters based on the value of
sort_order[character].
ctype[] is an array of bit values, with one element for one character.
(Note that to_lower[], to_upper[] and sort_order[]
are indexed by character value, but ctype[] is indexed by character
value + 1. This is an old legacy to be able to handle EOF.)
You can find the following bitmask definitions in `m_ctype.h':
#define _U 01 /* Upper case */ #define _L 02 /* Lower case */ #define _N 04 /* Numeral (digit) */ #define _S 010 /* Spacing character */ #define _P 020 /* Punctuation */ #define _C 040 /* Control character */ #define _B 0100 /* Blank */ #define _X 0200 /* heXadecimal digit */The
ctype[] entry for each character should be the union of the
applicable bitmask values that describe the character.
For example, 'A' is an uppercase character (_U) as well as a
hexidecimal digit (_X), so ctype['A'+1] should contain the value:
_U + _X = 01 + 0200 = 0201
CHARSETS_AVAILABLE list in
configure.in.
If you are creating a multi-byte character set, you can use the
_MB macros. In `include/m_ctype.h.in', add:
#define MY_CHARSET_MYSET X #if MY_CHARSET_CURRENT == MY_CHARSET_MYSET #define USE_MB #define USE_MB_IDENT #define ismbchar(p, end) (...) #define ismbhead(c) (...) #define mbcharlen(c) (...) #define MBMAXLEN N #endif
Where:
MY_CHARSET_MYSET | A unique character set value. |
USE_MB | This character set has multi-byte
characters, handled by ismbhead() and mbcharlen()
|
USE_MB_IDENT | (optional) If defined, you can use table and column names that use multi-byte characters |
ismbchar(p, e) | return 0 if p is not a multi-byte
character string, or the size of the character (in bytes) if it is. p
and e point to the beginning and end of the string.
Check from (char*)p to (char*)e-1.
|
ismbhead(c) | True if c is the first character of
a multi-byte character string
|
mbcharlen(c) | Size of a multi-byte character string if
c is the first character of such a string
|
MBMAXLEN | Size in bytes of the largest character in the set |
When started with the --log-update=file_name option, mysqld
writes a log file containing all SQL commands that update data. The file is
written in the data directory and has a name of file_name.#, where
# is a number that is incremented each time you execute
mysqladmin refresh or mysqladmin flush-logs, the FLUSH
LOGS statement, or restart the
server.
If you use the --log or -l options, the filename is
`hostname.log', and restarts and refreshes do not cause a new log file
to be generated. By default, the mysql.server script starts the
MySQL server with the -l option. If you need better
performance when you start using MySQL in a production environment,
you can remove the -l option from mysql.server.
Update logging is smart since it logs only statements that really update
data. So an UPDATE or a DELETE with a WHERE that finds no
rows is not written to the log. It even skips UPDATE statements that
set a column to the value it already has.
If you want to update a database from update log files, you could do the following (assuming your log files have names of the form `file_name.#'):
shell> ls -1 -t -r file_name.[0-9]* | xargs cat | mysql
ls is used to get all the log files in the right order.
This can be useful if you have to revert to backup files after a crash and you want to redo the updates that occurred between the time of the backup and the crash.
You can also use the update logs when you have a mirrored database on another host and you want to replicate the changes that have been made to the master database.
MySQL itself has a 4G limit on table size, and operating systems have their own file size limits. On Linux, the current limit is 2G; on Solaris 2.5.1, the limit is 4G; on Solaris 2.6, the limit is going to be 1000G. Currently, table sizes are limited to either 4G (the MySQL limit) or the operating system limit, whichever is smaller. To get more than 4G requires some changes to MySQL that are on the TODO. See section F List of things we want to add to MySQL in the future (The TODO).
If your big table is going to be read-only, you could use pack_isam
to merge and compress many tables to one. pack_isam usually
compresses a table by at least 50%, so you can have, in effect, much bigger
tables.
See section 12.3 The MySQL compressed read-only table generator.
Another solution can be the included MERGE library, which allows you to handle a collection of identical tables as one. (Identical in this case means that all tables are created with identical column information.) Currently MERGE can only be used to scan a collection of tables because it doesn't support indexes. We will add indexes to this in the near future.
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