Nuno, thanks for the tips. I think I will work on getting mk-query-digest to log to a db table and run it periodically. Sounds like a very useful thing to have.
-- Milan On Sun, Aug 2, 2009 at 10:02 AM, <nuno.tava...@dri.pt> wrote: > Hi Milan, > > I can see many ways of accomplish what you want: > * I'm almost sure mk-query-digest will allow you to do so; > * Either crop the slow query log for the desired timespan (that's a couple of > shell scripting commands) and run mk-query-digest against it; > * Set the query log file to a filename which is a link to /dev/null and set a > cron script to relink it to a real filename at noon and another to relink it > to > /dev/null at 1pm - and then run the scripts you want. > * In newer versions you can log the slow queries to tables for analysis; > * Ultimately, you can also try a patched version of mysqldumpslow I was using > for some time, explained here: > http://gpshumano.blogs.dri.pt/2009/07/04/analysing-mysql-slow-queries/ > > In the last two options you'll be logging to a table, so it will be easy to > select a timed range of queries for consideration. > > Hope that helps, > -NT > > Quoting Milan Andric <mand...@gmail.com>: > >> Thanks for the quick replies guys. I won't be pulling queries our of >> Drupal anytime soon. The optimizations I will do are minimal. Sounds >> like we might just have to live with mediocre performance for now. >> >> I will definitely looks further at maatkit though. I actually ran it >> mk-query-digest on my slow log and it's pretty amazing output. Lots >> there but it might take me a while to digest it all. And it does have >> a time span for the queries it spots, like: >> >> # Time range 2009-07-31 06:46:48 to 2009-07-31 12:51:21 >> >> Which is pretty helpful, but ideally I would like to pass args to >> mk-query-digest to list specific queries that were slow between noon >> and 1pm for example. If anyone happens to know how to that it would >> be helpful. Otherwise I will keep grokking maatkit tools. >> >> Thanks, >> >> Milan >> >> >> On Fri, Jul 31, 2009 at 3:14 PM, Johan De Meersman<vegiv...@tuxera.be> >> wrote: >> > On Fri, Jul 31, 2009 at 8:14 PM, Milan Andric <mand...@gmail.com> wrote: >> > Hello, >> > >> > I'm serving a burly Drupal install and at some points throughout the >> > day the mysql threads go way up and iowait peaks. I'm not sure which >> > is causing which but during this time the server is unresponsive. I >> > would like to determine if there is a poorly optimized query causing >> > this. >> > >> > Drupal is a disaster :-) >> > >> > I'm running a dozen drupals, and we've spent the last eight months heavily >> > optimizing every aspect. It's reasonably good now, but I'd still like to >> > move away from it. >> > >> > Drupal wants to remain compatible with multiple databases, notably both >> > MySQL and Postgres, and for v7 also Oracle. This means that they can't >> > optimize their DB layer and use the fancy tricks of a single DB, but must >> do >> > things in ways that are compatible with all of them. Postgres doesn't have >> > autoincrement ? No autoincrement. Mysql doesn't have sequences ? No >> > sequences. >> > >> > Some points: >> > - Drupal uses it's own internal unique ID system, not autoincrement, for >> a >> > number of things. This means that every insert that uses this locks all >> > other inserts that use this. >> > - Drupal has the bothersome tendency to do full table locks around some >> > inserts. This means that even if you move to InnoDB, you'll still get full >> > table locks. We patched this out according to info found on drupal.org and >> > other sites. >> > - Drupal's innate caching mechanisms are DB bound. Fun and dandy, but >> > rather irritating if as soon as a busy page expires, a hundred threads all >> > try to update the same table at the same time. We implemented Memcached. >> > Patches, at least partial ones, are on drupal.org, but I know we did more >> > and better in-house. >> > - Drupal can cache fine for anonymous users, but once you're logged in, >> > it's nearly impossible to cache. We worked around this by basically making >> > 'static' cacheable pages, and pulling any dynamic content in through AJAX. >> > - Get rid of Drupal's views (in drupal, that is, not wat is called a view >> > in a database). They generate horribly inefficient queries. >> > - Full text search modules use MySQL's full text indices, but that's not >> > the best way of doing things. We implemented Sphinx search, there's an >> > existing drupal module for integration. >> > >> > There's lots more that was done, but I can't provide all that info because >> > a) it's company internal, and b) because I'm not a developer and thus >> don't >> > know half of it :-) >> > >> > Suffice it to say, I don't like drupal for high-traffic interactive sites. >> > Get away from it if you can. >> > >> > >> > >> > >> >> I'm logging slow queries but is there a way to see when the >> >> slow queries take place also? I'd like to know what queries are being >> >> processed during this window of poor response time, usually around >> >> noon local time. >> > >> > If you want more than just the slow queries, you'll have to enable the >> full >> > log. Be aware that this has noticeable impact on performance, and will >> spam >> > your disks. Log on different spindles if able, and monitor your disk usage >> > carefully - mysql stops functioning if it can't write logs. >> > >> > >> > >> > >> > -- >> > Celsius is based on water temperature. >> > Fahrenheit is based on alcohol temperature. >> > Ergo, Fahrenheit is better than Celsius. QED. >> > >> >> -- >> MySQL General Mailing List >> For list archives: http://lists.mysql.com/mysql >> To unsubscribe: http://lists.mysql.com/mysql?unsub=nuno.tava...@dri.pt >> >> > > > -- > Nuno Tavares > +351 93 618 40 86 > dri Consultoria Informatica > > -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
