Even prior to the group by it's still not likely to ever be more than 200 or so maximum.
I have the sort_buffer_size at 256Mb so I don't believe it's that either :( On Thu, Sep 9, 2010 at 3:16 PM, Michael Dykman <mdyk...@gmail.com> wrote: > How many rows before the GROUP BY? Group by is, in effect a sorting > process.. perhaps that contains enough data to justify going to disk. > > What is the value of the variable sort_buffer_size? > show variables like '%sort%'; > > - md > > On Thu, Sep 9, 2010 at 3:04 PM, Phil <freedc....@gmail.com> wrote: > > On average it would be between 10 and 40, certainly no more than 100. > > > > > > On Thu, Sep 9, 2010 at 2:57 PM, Michael Dykman <mdyk...@gmail.com> > wrote: > >> > >> The filesort is probably necessary because of the number of rows in > >> the result set to be ordered. How many rows do you get out of this > >> query? > >> > >> - michael dykman > >> > >> On Thu, Sep 9, 2010 at 1:53 PM, Phil <freedc....@gmail.com> wrote: > >> > I wonder if anyone could help with a query which I've been unable to > >> > prevent > >> > from using a filesort. Might be something obvious I'm overlooking! > >> > > >> > I have a table which tracks milestones in distributed computing > projects > >> > > >> > Create Table: CREATE TABLE `boinc_milestone` ( > >> > `proj` char(6) NOT NULL, > >> > `id` int(11) NOT NULL, > >> > `stat_date` date NOT NULL DEFAULT '0000-00-00', > >> > `milestone_type` char(1) NOT NULL DEFAULT '0', > >> > `milestone` double NOT NULL DEFAULT '0', > >> > `cpid` varchar(32) DEFAULT NULL, > >> > `team` int(11) DEFAULT NULL, > >> > PRIMARY KEY (`proj`,`id`,`stat_date`,`milestone`), > >> > KEY `two` (`proj`,`stat_date`,`id`,`milestone`), > >> > KEY `cpid` (`cpid`,`proj`,`id`,`stat_date`,`milestone`), > >> > KEY `team` (`proj`,`team`,`id`,`stat_date`,`milestone`) > >> > ) ENGINE=MyISAM DEFAULT CHARSET=latin1 > >> > > >> > These are added to on a daily basis as users pass the various credit > >> > milestones so for instance you can end up with rows for > >> > 1000,5000,10000,50000,1000000 etc on different dates as time goes on. > >> > > >> > Now on one page for display I want to show the latest milestone for > each > >> > project for a particular cpid. The query I use is as follows: > >> > > >> > select a.proj,a.id,max(stat_date),max(a.milestone) as > >> > milestone,b.description > >> > from boinc_milestone a join boinc_projects b on a.proj = > b.proj > >> > where cpid = '$cpid' > >> > group by proj > >> > order by stat_date desc > >> > > >> > The order by causes the filesort and I can't find an easy way around > it. > >> > > >> > mysql> explain select a.proj,a.id,max(stat_date),max(a.milestone) as > >> > milestone,b.description from boinc_milestone a join boinc_projects b > on > >> > a.proj = b.proj where cpid = 'XXX' group by proj order by stat_date\G > >> > *************************** 1. row *************************** > >> > id: 1 > >> > select_type: SIMPLE > >> > table: a > >> > type: ref > >> > possible_keys: PRIMARY,two,cpid,team > >> > key: cpid > >> > key_len: 35 > >> > ref: const > >> > rows: 1 > >> > Extra: Using where; Using index; Using temporary; Using > filesort > >> > *************************** 2. row *************************** > >> > id: 1 > >> > select_type: SIMPLE > >> > table: b > >> > type: eq_ref > >> > possible_keys: PRIMARY > >> > key: PRIMARY > >> > key_len: 10 > >> > ref: stats.a.proj > >> > rows: 1 > >> > Extra: Using where > >> > 2 rows in set (0.00 sec) > >> > > >> > I could just remove the order by altogether and perform the sort in > php > >> > afterwards I guess but any other ideas? > >> > > >> > Thanks > >> > > >> > Phil > >> > > >> > -- > >> > Distributed Computing stats > >> > http://stats.free-dc.org > >> > > >> > >> > >> > >> -- > >> - michael dykman > >> - mdyk...@gmail.com > >> > >> May the Source be with you. > > > > > > > > -- > > Distributed Computing stats > > http://stats.free-dc.org > > > > > > -- > - michael dykman > - mdyk...@gmail.com > > May the Source be with you. > -- Distributed Computing stats http://stats.free-dc.org
