Calculation queries do not take eager loading into account
Reported by Lawrence Pit | July 3rd, 2008 @ 07:20 AM | in 2.x
When :include is used with a find (or defined within a scope), like for example:
Project.scoped({:include => categories}).find(:limit => 15)
then execution of this results in e.g. these queries:
Project Load (0.005413) SELECT projects.id, title FROM `projects` LIMIT 0, 15
Category Load (0.003505) SELECT `categories`.*, t0.project_id as _parent_record_id FROM `categories` INNER JOIN `categories_projects` as t0 ON `categories`.id = t0.category_id WHERE (t0.project_id IN (1298,1275,1274,1273,1270,1269,1264,1261,1260,1259,1258,1257,1256,1254,1253))
So far so good.
However, when a count is executed on the same scope, the query is like:
SQL (0.013835) SELECT count(DISTINCT `projects`.id) AS count_all FROM `projects` LEFT OUTER JOIN `categories_projects` ON `categories_projects`.project_id = `projects`.id LEFT OUTER JOIN `categories` ON `categories`.id = `categories_projects`.category_id
I expected, based on the first "Project Load" query executed:
SELECT count(DISTINCT `projects`.id) AS count_all FROM `projects`
which should perform a lot better.
Comments and changes to this ticket
-
Joshua Peek October 5th, 2008 @ 03:18 PM
- → State changed from “new” to “stale”
Please Login or create a free account to add a new comment.
You can update this ticket by sending an email to from your email client. (help)
Create your profile
Help contribute to this project by taking a few moments to create your personal profile. Create your profile »
Source available from github
The Git repository resides at http://github.com/rails
Check out the current development trunk (Edge Rails) with:
git clone git://github.com/rails/rails.git
Creating or reviewing a patch
See the contributor guide.
Creating a feature request
Please don't. If you want a new feature in Rails, you'll have to pull up your sleeves and get busy yourself. Or convince someone else to do it. See the contributor guide on how to get going. But posting them here is just going to lead to ticket root.
Creating a bug report
When creating a bug report, be sure to include as much relevant information as possible. Post the code sample that causes the problem. Preferably, alter the unit tests and show through either changed or added tests how the expected behavior is not occuring.
Security vulnerabilities should be reported via an email to security@rubyonrails.org, do not use trac for reporting security vulnerabilities. All content in trac is publicly available as soon as it is posted.
Then don't get your hopes up. Unless you have a "Code Red, Mission Critical, The World is Coming to an End" kinda bug, you're creating this ticket in the hope that others with the same problem will be able to collaborate with you on solving it. Do not expect that the ticket automatically will see any activity or that others will jump to fix it. Creating a ticket like this is mostly to help yourself start on the path of fixing the problem and for others to sign on to with a "I'm having this problem too".
