Rails - Aug 2014 - Should includes work with a query that returns the same object more than once?

My app has models Person, Photo, Comment. A Comment has_many Photos and a 
Photo has_many People.

In the console, with a database with some data in it and the ActiveRecord 
logger sent to STDOUT ...

First, to show what's in the data:

irb(main):003:0> Photo.joins(:comments).order(:id).limit(2).map &:id 
D, [2014-08-05T18:19:10.528376 #24027] DEBUG -- :   Photo Load (20.6ms)  
SELECT  `photos`.* FROM `photos` INNER JOIN `comments` ON 
`comments`.`photo_id` = `photos`.`id`  ORDER BY `photos`.`id` ASC LIMIT 2
=> [1, 1]

Photo.joins(:comments).order(:id).limit(2) returns the same photo twice, 
because it has two comments. That's what I want. (This is cut down from a 
much larger query where this behavior is actually useful.) Now for the 
problem:

irb(main):001:0> 
Photo.joins(:comments).includes(:person).order(:id).limit(2).each { |f| 
puts f.person.username }; nil
D, [2014-08-05T18:17:44.613676 #24027] DEBUG -- :   Photo Load (0.6ms)  
SELECT  `photos`.* FROM `photos` INNER JOIN `comments` ON 
`comments`.`photo_id` = `photos`.`id`  ORDER BY `photos`.`id` ASC LIMIT 2
D, [2014-08-05T18:17:44.811715 #24027] DEBUG -- :   Person Load (0.3ms)  
SELECT `people`.* FROM `people`  WHERE `people`.`id` IN (1)
user1
D, [2014-08-05T18:17:44.845897 #24027] DEBUG -- :   Person Load (0.6ms)  
SELECT  `people`.* FROM `people`  WHERE `people`.`id` = 1 LIMIT 1
user1

Even though I said includes(:person), and it did cause ActiveRecord to 
issue the second query to get all the people, when I retrieve the second 
Photo's Person ActiveRecord has to query it again. With a production query 
with many more photos and people it's very slow.

Is this a bug? Is includes not supported with a query that returns the same 
object more than once? Is there a way around the N + 1 queries?

Thanks!


-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To view this discussion on the web visit
https://groups.google.com/d/msgid/rubyonrails-talk/1279d510-aea0-4b03-83ac-d78ee8a2507d%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.