On Feb 24, 9:23 pm, William Fisk <[email protected]> wrote: > Has anyone experienced an ActiveRecord query being much much slower than > running the equivalent > query in the MySql console? > > I am running a simple "group by" query with one condition on a table with 7 > million records. When > I run EXPLAIN it says that it will have to scan over all the records - well > that's OK. In the MySQL > query it takes 1min 40secs which is OK for me - this is not a web app. But > when I run exactly > the same query in a ruby script using ActiveRecord it takes about 45 mins - > far too long. > I'd try using ruby-prof to see where the time is being spent (bear in mind that ruby-prof does slow down the execution of ruby code, but it should still give you an idea)
Fred > I am running all this on my work PC, 3 gig of memory. Windows PerfMon says > I have 2 gig available > and 1 gig on standyby. I am using ruby 1.8.7; rails 3; mysql2 gem; Windows > 7 and MySql 5.5. > I have also set the INNODB buffer pool size to 480M. > > What seems to be happening is that the MySQL process uses all the memory up > to 500M and > there is a lot of page swapping. PerfMon shows that the disk activity is > very high (99%). So > that explains the bottleneck. But I still don't know why this happens when > I run the code from > Ruby and yet from the MySQL console it is fine. > > I even tried just using the MySQL2 gem directly in my ruby code using > MySql2::Client.new, > but still very very slow. > > I know this probably doesn't explain everything but I just wondered if > anyone had a similar experience. > > Thanks > > William > > p.s. also posed on > StackOverflow.http://stackoverflow.com/questions/5004204/query-is-fast-in-mysql-but... -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
