From: Zardosht Kasheff
Date: January 12 2010 7:14pm
Subject: consequences of HTON_FLUSH_AFTER_RENAME
List-Archive: http://lists.mysql.com/internals/37636
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Hello,

I was wondering what the purpose of HTON_FLUSH_AFTER_RENAME is for
handertons. It seems exposing this flag causes a call to "flush logs"
after any "alter table". Is there any other purpose? The relevant code
seems to be the following in sql_table.cc:

  if (ha_check_storage_engine_flag(old_db_type, HTON_FLUSH_AFTER_RENAME))
  {
    /*
      For the alter table to be properly flushed to the logs, we
      have to open the new table.  If not, we get a problem on server
      shutdown. But we do not need to attach MERGE children.
    */
    char path[FN_REFLEN];
    TABLE *t_table;
    build_table_filename(path, sizeof(path), new_db, table_name, "", 0);
    t_table= open_temporary_table(thd, path, new_db, tmp_name, 0);
    if (t_table)
    {
      intern_close_table(t_table);
      my_free(t_table, MYF(0));
    }
    else
      sql_print_warning("Could not open table %s.%s after rename\n",
                        new_db,table_name);
    ha_flush_logs(old_db_type);
  }


I see the last line calls "flush logs". I do not understand what the
code before that does.

-Zardosht