Rails Ruby on Rails → 3.0.2

Comments and changes to this ticket

• You flagged this item as spam.
  

  Jason May March 20th, 2010 @ 04:18 PM

  • no changes were found...

• You flagged this item as spam.
  

  Jason May March 20th, 2010 @ 04:18 PM

  • Tag changed from “arel activerecord bug rails3, eager, eager_loading” to “activerecord 3.0, rails 3, activerecord, arel, eager, eager_loading”
• 

  Emilio Tagua March 22nd, 2010 @ 01:27 PM

  Hey Jason,

  Can you provide a failing test or something more specific, because i tried this on master:

  Post.joins(:comments).includes(:comments).all

  and you get this 2 queries:

  SELECT "posts". FROM "posts" INNER JOIN "comments" ON "comments"."post_id" = "posts"."id"
  SELECT "comments". FROM "comments" WHERE ("comments".post_id IN (1,2,4,5,7)).

  Which shows eager loading is working properly.

• You flagged this item as spam.
  

  Jason May March 22nd, 2010 @ 05:53 PM

  I see...

  I had thought that includes(:bar) would generate an OUTER JOIN clause in the original SQL, rather than generating a second SELECT with an IN clause, i.e.

  Post.includes(:comments).all
  

  would generate (for has_many)

  SELECT "posts".*, "comments".* FROM "posts" LEFT OUTER JOIN "comments" ON "comments"."post_id" = "posts"."id"
  

  instead of

  SELECT "posts".* FROM "posts"
  SELECT "comments". FROM "comments" WHERE ("comments".post_id IN (...))
  

  My problem is that the 2-query situation doesn't allow for iterating through the results without pre-fetching everything. Doesn't that bust Arel's closure objective?

• 

  José Valim March 26th, 2010 @ 11:05 PM

  • Assigned user set to “Emilio Tagua”
  • Milestone cleared.
• 

  Emilio Tagua March 27th, 2010 @ 02:05 AM

  • State changed from “new” to “invalid”

  Hey Jason,

  This 2 queries is the expected behavior, you would get one query with an OUTER JOIN if any restriction includes a reference in conditions, order, etc. in the other table (check out references_eager_loaded_tables? in ActiveRecord::Relation).

  Fox exmaple:

  Post.find(:first, :include => :comments, :conditions => "posts.title = 'Welcome to the weblog'")

  When this doesn't happen preload is used which executes this 2 queries, which do pre-fetch everything in a better way, that 2 queries are better than having just 1 with a join by default.

  I'm marking this ticket as invalid as it doesn't look like a bug but feel free to continue discussing if i'm not making things clear for you.

• You flagged this item as spam.
  

  Jason May March 30th, 2010 @ 01:31 AM

  Hi Emilio-

  I think your example should have comments.title in the conditions instead of post.title.

  Is it possible to express your example using Arel-style syntax? Something like

  Post.includes(:comment).where(comment[:title].eq("Welcome..."))
  

  I'm not sure how to refer to comment here, the example code I could find refers to an Arel::Table method but this seems to be private.

  Thanks,
  -Jason

• 

  Emilio Tagua March 31st, 2010 @ 01:45 PM

  Jason,

  You could try something like this:

  Post.includes(:comments).where(Comment.arel_table[:title].eq("Welcome ..."))
  

• 

  Ryan Bigg October 9th, 2010 @ 10:10 PM

  • Tag cleared.
  • Importance changed from “” to “Low”

  Automatic cleanup of spam.

• 

  Ryan Bigg October 11th, 2010 @ 12:13 PM

  Automatic cleanup of spam.

• 

  Jeremy Kemper October 15th, 2010 @ 11:01 PM

  • Milestone set to “3.0.2”

  [bulk edit]

• 

  Ryan Bigg October 21st, 2010 @ 03:36 AM

  Automatic cleanup of spam.

• 

  Jeff Kreeftmeijer November 8th, 2010 @ 08:54 AM

  Automatic cleanup of spam.