mysql5.5.25 源码阅读---rename处理流程

在rename的处理过程中，frm ibd文件都是直接改名，并没有将原表数据导入新表的过程，所以速度还是很快。
drop 比较大的表时可以利用下这个特点
可以先rename，
然后结合这个方法异步进行http://www.mysqlops.com/2011/05/18/mysql%E5%88%A0%E9%99%A4%E5%A4%A7%E8%A1%A8%E6%9B%B4%E5%BF%AB%E7%9A%84drop-table%E5%8A%9E%E6%B3%95.html


sql_rename.cc::do_rename
  build_table_filename(name, sizeof(name) - 1,new_db, new_alias, reg_ext, 0);
 
  build_table_filename(name, sizeof(name) - 1,ren_table->db,old_alias,reg_ext, 0);
  switch (frm_type)
  {
    case FRMTYPE_TABLE:
    {
       ## rename table
       if (!(rc= mysql_rename_table(ha_resolve_by_legacy_type(
                                    thd,table_type),
                                    ren_table->db,old_alias,
                                    new_db, new_alias
                                    , 0)))
       {
          ## 改触发器引用的原表名
          if ((rc= Table_triggers_list::change_table_name(thd, ren_table->db,
                                                          old_alias,
                                                          ren_table->table_name,
                                                          new_db,
                                                          new_alias)))
          {
            ## 失败进行回滚
            (void) mysql_rename_table(ha_resolve_by_legacy_type(thd,table_type),
                                   new_db, new_alias,ren_table->db, old_alias, 0);
          }
        }
      }
      break;


#################################################
sql_table.cc::mysql_rename_table
-->handler.cc::ha_rename_table
-->ha_innobase.cc::rename_table
    innobase_trx_allocate(thd);

    HA_innobase.cc::innobase_rename_table(trx, from, to, TRUE);
      ## 数据字典lock
      row_mysql_lock_data_dictionary(trx);

      Row0mysql.c::row_rename_table_for_mysql(norm_from, norm_to, trx, TRUE)
        ## 获取原表的字典信息
        table = dict_table_get_low(old_name);
        ## 外键约束处理
        dict_foreign_parse_drop_constraints(**);
        for (****) {
          row_mysql_unlock_data_dictionary(trx);
          os_thread_yield();
          row_mysql_lock_data_dictionary(trx);
        }
       
              
        ## 用parse来进行处理，frm改名
        info = pars_info_create();
        pars_info_add_str_literal(info, "new_table_name", new_name);
        pars_info_add_str_literal(info, "old_table_name", old_name);
        err = que_eval_sql(info,
                           "PROCEDURE RENAME_TABLE () IS\n"
                           "BEGIN\n"
                           "UPDATE SYS_TABLES SET NAME = :new_table_name\n"
                           " WHERE NAME =ld_table_name;\n"
                           "END;\n"
                          , FALSE, trx);
      

        ## 如果是独立表空间，rename the .ibd data file
        ## 更新相关数据字典信息。比如索引、外键等
        Dict0dict.c::dict_table_rename_in_cache
          ## ibd data file 改名
          Fil0fil.c::fil_rename_tablespace
        

         ## 恢复原表约束关系
         dict_load_foreigns(new_name, FALSE, !old_is_tmp || trx->check_foreigns);

       ## 释放数据字典lock
       row_mysql_unlock_data_dictionary(trx);

       ## flush log buffer
       ## 防止innodb_flush_log_at_trx_commit = 0时数据字典不一致
       log_buffer_flush_to_disk();

    srv_active_wake_master_thread();
    innobase_commit_low(trx);
    trx_free_for_mysql(trx);