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Re: Optimized Indexing for a Schedule Table
Posted by: Rick James
Date: November 26, 2010 01:42PM

Hmmm...

INDEX(state, priority, fire_time);
This one should have the following characteristics:
* The query will be "Using index"
* Hopefully the ORDER BY will use the index, then filter on fire_time.
* There are often enough with the correct `state` to meet the LIMIT
* There are often enough with the priority=0 (or small number) to meet the LIMIT

What is the value of innodb_buffer_pool_size? autocommit? How much RAM do you have?

Why are there 3M rows in the table? Sounds like you have a huge backlog of things to do.

Is it always LIMIT 10?

It may be worth it to do something like
for $prio = 0, 1, ...
   SELECT ...
          where state='ARMED'
            and priority = $prio
            and fire_time < 20101127
          order by fire_time
          limit 10; 
   IF got some rows, process them and exit loop

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