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 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-slow-when-run-from-rails-activerecord -- 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.
