Pre-General Availability Draft: 2018-03-17
This section discusses the procedure for adding a character set to MySQL. The proper procedure depends on whether the character set is simple or complex:
If the character set does not need special string collating routines for sorting and does not need multibyte character support, it is simple.
If the character set needs either of those features, it is complex.
are simple character sets, whereas
czech are complex character sets.
To use the following instructions, you must have a MySQL source
distribution. In the instructions,
MYSET represents the name of the
character set that you want to add.
sql/share/charsets/Index.xmlfile. Use the existing contents in the file as a guide to adding new contents. A partial listing for the
<charset name="latin1"> <family>Western</family> <description>cp1252 West European</description> ... <collation name="latin1_swedish_ci" id="8" order="Finnish, Swedish"> <flag>primary</flag> <flag>compiled</flag> </collation> <collation name="latin1_danish_ci" id="15" order="Danish"/> ... <collation name="latin1_bin" id="47" order="Binary"> <flag>binary</flag> <flag>compiled</flag> </collation> ... </charset>
<charset>element must list all the collations for the character set. These must include at least a binary collation and a default (primary) collation. The default collation is often named using a suffix of
general_ci(general, case insensitive). It is possible for the binary collation to be the default collation, but usually they are different. The default collation should have a
primaryflag. The binary collation should have a
You must assign a unique ID number to each collation. The range of IDs from 1024 to 2047 is reserved for user-defined collations. To find the maximum of the currently used collation IDs, use this query:
SELECT MAX(ID) FROM INFORMATION_SCHEMA.COLLATIONS;
This step depends on whether you are adding a simple or complex character set. A simple character set requires only a configuration file, whereas a complex character set requires C source file that defines collation functions, multibyte functions, or both.
For a simple character set, create a configuration file,
, that describes the character set properties. Create this file in the
sql/share/charsetsdirectory. You can use a copy of
latin1.xmlas the basis for this file. The syntax for the file is very simple:
Comments are written as ordinary XML comments (
<map>array elements are separated by arbitrary amounts of whitespace.
Each word within
<map>array elements must be a number in hexadecimal format.
<map>array element for the
<ctype>element has 257 words. The other
<map>array elements after that have 256 words. See Section 10.12.1, “Character Definition Arrays”.
For each collation listed in the
<charset>element for the character set in
must contain a
<collation>element that defines the character ordering.
For a complex character set, create a C source file that describes the character set properties and defines the support routines necessary to properly perform operations on the character set:
Create the file
stringsdirectory. Look at one of the existing
ctype-*.cfiles (such as
ctype-big5.c) to see what needs to be defined. The arrays in your file must have names like
to_lower_, and so on. These correspond to the arrays for a simple character set. See Section 10.12.1, “Character Definition Arrays”.
<collation>element listed in the
<charset>element for the character set in
ctype-file must provide an implementation of the collation.
If the character set requires string collating functions, see Section 10.12.2, “String Collating Support for Complex Character Sets”.
If the character set requires multibyte character support, see Section 10.12.3, “Multi-Byte Character Support for Complex Character Sets”.
Modify the configuration information. Use the existing configuration information as a guide to adding information for
MYSYS. The example here assumes that the character set has default and binary collations, but more lines are needed if
MYSEThas additional collations.
mysys/charset-def.c, and “register” the collations for the new character set.
Add these lines to the “declaration” section:
#ifdef HAVE_CHARSET_MYSET extern CHARSET_INFO my_charset_MYSET_general_ci; extern CHARSET_INFO my_charset_MYSET_bin; #endif
Add these lines to the “registration” section:
#ifdef HAVE_CHARSET_MYSET add_compiled_collation(&my_charset_MYSET_general_ci); add_compiled_collation(&my_charset_MYSET_bin); #endif
If the character set uses
ctype-to the definition of the
MYSETto the value of with
CHARSETS_AVAILABLEin alphabetic order.
MYSETto the value of
CHARSETS_COMPLEXin alphabetic order. This is needed even for simple character sets, or CMake will not recognize
Reconfigure, recompile, and test.