Writing Storage Engines for MySQL

MySQL UC2005

by Brian Aker

MySQLのDirector of Architectureによるストレージエンジンの作り方解説：

  • Starting points for coding：
-sql/ is for the kernel
-mysys/ is the portable runtime
-mysql-test is for you test cases
  • Terms:Storage Engine, Handler (This is the code that controls the storage engine)
  • What does it take?: All code is written in simplified C++, An example storage engine, your ideas
  • People who implemented storage engine: Friendster, Google, Yahoo (contributed ideas, thanks Jeremy!!)
  • server's kernel:
DDL > Query cache > rewrite engine > parser > optimizer > hander > strage engine
DML > rewrite engine > parser > optimizer > hander > strage engine
  • What is a storage engine?: Data formats on disk
  • What do I need to do to add field:
- Subclass Field in field.h
- implements a few method 
  Storage:store(string), store(long long), store(double)
  Retrieve:val_real(), val_int(), val_str()
  Other:field_cast_type(), result_type(), cmp(), sort_string(), max_length()
  • Field Store Example:
int Field_ipaddrv4::store(const char *from, uint length, CHARSET_INFO *cs) {
  int count;
  count = sscan(from,"%u.%u.%u.%u" ptr, (ptr+1),(ptr+2),(ptr+3));
  if(count!=4) {
    bzero(ptr,4);
    return -1;
  }
  return 0;
}
  • Storage Engine Methods types:
Table Control: create(), open(), close(), delete_table() 
Optimizer: info(), records_in_range()
SQL Modifiers: insert_row(), delete_row(), write_row(), update_row()
SQL Readers: [Scan Reads] rnd_init(), md_init(), md_next(), position(), rnd_pos(), mod_pos()
             [Index Reads] index_read(), index_next()
  • Transaction methods　←more complex!!
  • Bulk load methods
  • Defrag methods
  • Lot more (read handler.h)
  • Autoconf: Create a new rule in config/ac-macros(look at ha_example file), add your ruleto be checked in configure.in
  • Additional Files: basic server files modified under sql/
sql/Makefile.am  ..add your include and source file
sql/handler.h    ..register your handler
sql/mysql_priv.h ..set up your variable for show variabes
sql/handler.cc   ..add yourself to the handler create list
sql/mysqld.cc    ..set up your variable for show
sql/set_var.cc   ..add your variable for SHOW display
  • Test Cases
mysql-test/include/have_mmap.inc
mysql-test/mmap.test
mysql-test/???
  • other thoughts: what is your goal? (read only? durable? network?)
  • more information: sql/ha_example.[h|cc] , mysql.com , list , support

感想．昨日のアレよりもテクニカル，実践的．とりあえず"sql/ha_example"見れ．Brianさんお疲れ様です．今回のUCのセッションはこれにて終了．あとはTim O'Reilly氏のスピーチのみ．