Is it possible to do a non-blocking read of MyISAM table?

Question

I have a log table with heavy write operations: that was the reason of choosing MyISAM for it.

Now I need to execute a complicated SELECT query which takes a lot time and blocks the table: no one can write to it then.

• The table has a high 'write' load
• I don't care if I don't get the most recent records
• The data is never deleted

What are the options to read the data without blocking the table?

• LIMIT is applied after the query is completed, so is not an option
• Modifying all INSERT statements to make them DELAYED is not an option
• InnoDB is also is not an option
• HANDLER query is not an option: I need complex WHERE conditions

Answer 1

Some suggestions, maybe one or the other is suitable for you

1. option: Slave

   Configure a slave that you use for your SELECT query. That won't block the inserts. However, this requires a second server, some configuration and storage space, so this is not a good solution, just to get your data.

2. option: use low-priority-updates: http://dev.mysql.com/doc/refman/5.0/en/table-locking.html

   This can be done on a server level or connection level, so you don't have to modify every insert statement.

3. worker process

   • Make your inserts as usual.
   • create a worker process that "moves" your log entries (for each row in table A, make a insert in table B, delete row in Table A) to another table.
   • Now you can query Table B