Drizzle’s Data Dictionary and Global Status

With the recent news by Brian about the Data Dictionary in Drizzle replacing the INFORMATION_SCHEMA, I was looking into the server status variables (aka INFORMATION_SCHEMA.GLOBAL_STATUS) and I came across an interesting discovery.

select * from data_dictionary.global_status;
...
| Table_locks_immediate      | 0              |
| Table_locks_waited         | 0              |
| Threads_connected          | 8134064        |
| Uptime                     | 332            |
| Uptime_since_flush_status  | 332            |
+----------------------------+----------------+
51 rows in set (0 sec)

This only retrieved 51 rows, which is way less then previous. What I wanted was clearly missing, all the old com_ status variables. Looking at what the data_dictionary actually has available revealed a new table.

drizzle> select * from data_dictionary.global_statements;
+-----------------------+----------------+
| VARIABLE_NAME         | VARIABLE_VALUE |
+-----------------------+----------------+
| admin_commands        | 0              |
| alter_db              | 0              |
| alter_table           | 0              |
| analyze               | 0              |
| begin                 | 0              |
| change_db             | 1              |
| check                 | 0              |
| checksum              | 0              |
| commit                | 0              |
| create_db             | 0              |
| create_index          | 0              |
| create_table          | 0              |
| delete                | 0              |
| drop_db               | 0              |
| drop_index            | 0              |
| drop_table            | 0              |
| empty_query           | 0              |
| flush                 | 0              |
| insert                | 0              |
| insert_select         | 0              |
| kill                  | 0              |
| load                  | 0              |
| release_savepoint     | 0              |
| rename_table          | 0              |
| replace               | 0              |
| replace_select        | 0              |
| rollback              | 0              |
| rollback_to_savepoint | 0              |
| savepoint             | 0              |
| select                | 10             |
| set_option            | 0              |
| show_create_db        | 0              |
| show_create_table     | 0              |
| show_errors           | 0              |
| show_warnings         | 0              |
| truncate              | 0              |
| unlock_tables         | 0              |
| update                | 0              |
+-----------------------+----------------+
38 rows in set (0 sec)

Kudos to this. Looking at list I saw an obvious omission, of “ping”. Something that caught me out some years ago with huge (300-500 per second admin_commands). I’m also a fan of Mark’s recent work An evening hack – Com_ping in MySQL.

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3 Responses to “Drizzle’s Data Dictionary and Global Status”

  1. Baron says:

    | Threads_connected | 8134064 |

    That looks like a bug.

  2. Brian Aker says:

    Hi!

    We pulled that table out for the moment, but we have someone who is going through and reimplementing most of the core to this right now. I think it will go through a couple more iterations before it is done.

    Cheers,
    -Brian

  3. Brian Aker says:

    @Baron The entire variables/status code is one big giant hack that has no type safety at all. We are currently removing most of it and replacing it with something that actually tests values. If you look in my tree on Launchpad you can see the work happening there.