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Very slow sort on Order By for MySQL query.
Posted by: SlowQuery Shark ()
Date: June 26, 2011 12:01AM

Hi everybody! :-D

I have a problem on sorting fields. The Order By clause on a query is very slow on a table of 2 million rows - even when I have an index on the field.

Here is the table structure, I need to sort the data quickly by 'id', 'fld1' or 'fld2' depending on search criteria.

CREATE TABLE `tblM` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`fld1` varchar(1024) NOT NULL,
`fld2` varchar(1024) NOT NULL,
PRIMARY KEY (`id`),
KEY `fld1` (`fld1`(1000)),
KEY `fld2` (`fld2`(1000)),
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=21748375 ;

The query I use is:
SELECT id, fld1, fld2 FROM tblM ORDER BY fld2 ASC LIMIT 30

However this takes around 15 seconds to return a result. However when I short by id (the primary key) it takes only 0.0017 sec. Why is this?

How can I make this sort through the data of those fields in less than a second? Is this possible in MySQL? (Disk space does not matter, but the fact to order these rows in less than a second does. I tried looking at documentation and various other forums but nobody seems to know how to make it sort these fields in <1sec)



Edited 3 time(s). Last edit at 06/26/2011 12:36AM by SlowQuery Shark.

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Subject Written By Posted
Very slow sort on Order By for MySQL query. SlowQuery Shark 06/26/2011 12:01AM
Re: Very slow sort on Order By for MySQL query. Peter Brawley 06/26/2011 09:53AM
Re: Very slow sort on Order By for MySQL query. Rick James 07/05/2011 11:09PM


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