システム変数実装方法@set_var.ccの違い

mysql-5.0とmysql-5.1で異なっているようなので貼りつけておきます。

mysql-5.0での方法

  - Use one of the 'sys_var... classes from set_var.h or write a specific
    one for the variable type.
  - Define it in the 'variable definition list' in this file.
  - If the variable should be changeable or one should be able to access it
    with @@variable_name, it should be added to the 'list of all variables'
    list (sys_variables) in this file.
  - If the variable is thread specific, add it to 'system_variables' struct.
    If not, add it to mysqld.cc and an declaration in 'mysql_priv.h'
  - If the variable should be changed from the command line, add a definition
    of it in the my_option structure list in mysqld.cc
  - Don't forget to initialize new fields in global_system_variables and
    max_system_variables!
  - If the variable should show up in 'show variables' add it to the
    init_vars[] struct in this file

mysql-5.1での方法

  - Use one of the 'sys_var... classes from set_var.h or write a specific 
    one for the variable type. 
  - Define it in the 'variable definition list' in this file.       
  - If the variable is thread specific, add it to 'system_variables' struct.   
    If not, add it to mysqld.cc and an declaration in 'mysql_priv.h'   
  - If the variable should be changed from the command line, add a definition 
    of it in the my_option structure list in mysqld.cc    
  - Don't forget to initialize new fields in global_system_variables and    
    max_system_variables!

赤で色を付けた部分がなくなっています。mysql-5.0の改造をしていた時、このあたりが冗長だなぁと思っていたのですが、それがmysql-5.1ですっきり簡潔になったということかもしれません。