Re: very long query time

[Brent Baisley]

This is a shot in the dark, but perhaps you need to optimize your 
indexes. By default, MySQL assumes an even distribution of values for 
indexes. I'm not sure when it diverges from this default, I assume it 
does at some point. MySQL uses the data distribution values/assumptions 
to determine how to optimize a query.

Anyway, you can run myisamchk with the analyze option to have MySQL 
update it's value distribution for the indexes. This may or may not 
alter what decisions the MySQL optimizer works. I know a few people on 
this list have tried this "trick" and have seen considerable 
improvement in query speed.

On Friday, June 27, 2003, at 10:45 AM, Charles Vos wrote:

Thanks to everyone for their help, I actually managed to fix the 
problem by bypassing MySQL's optimization using STRAIGHT_JOIN.  Out of 
curiosity can anyone tell me why MySQL failed so miserably at 
optimizing my query? (The two hour long query took 10s with 
Straight_join).
--
Brent Baisley
Systems Architect
Landover Associates, Inc.
Search & Advisory Services for Advanced Technology Environments
p: 212.759.6400/800.759.0577
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