Comments on: Better in-memory associations with :inverse_of http://mediumexposure.com/better-memory-associations-inverseof/ by Maxim Chernyak Thu, 15 Jul 2010 14:57:57 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: hakunin http://mediumexposure.com/better-memory-associations-inverseof/comment-page-1/#comment-3284 hakunin Sat, 12 Jun 2010 21:49:29 +0000 #comment-3284 <p>Currently all relationship are one-way. A practical explanation would be that if you have:</p> <p><pre><code lang="ruby"> class Horse belongs_to :rider end class Rider has_many :horses end # controller @riders = Rider.all(:include => :horses) </code></pre></p> <p>You will end up eager-loading both riders and horses, that's great. So <code lang="ruby" inline="true">@riders.first.horse</code> will not run any extra SQL queries. However, <code lang="ruby" inline="true">@riders.first.horse.rider</code> <strong>will</strong> run an additional query to fetch the horse's rider. Because Rails won't know that they should be the same object. The comprehensive solution would be an identity map, but this commit was a start in the right direction.</p> Currently all relationship are one-way. A practical explanation would be that if you have:



class Horse

  belongs_to :rider

end



class Rider

  has_many :horses

end



# controller

@riders = Rider.all(:include => :horses)

You will end up eager-loading both riders and horses, that’s great. So @riders.first.horse will not run any extra SQL queries. However, @riders.first.horse.rider will run an additional query to fetch the horse’s rider. Because Rails won’t know that they should be the same object. The comprehensive solution would be an identity map, but this commit was a start in the right direction.

]]> By: Clay Shentrup http://mediumexposure.com/better-memory-associations-inverseof/comment-page-1/#comment-3283 Clay Shentrup Sat, 12 Jun 2010 21:40:17 +0000 #comment-3283 <p>Can you explain how inverse_of is in any way necessary? The relationships are already described via has_one and belongs_to.</p> Can you explain how inverse_of is in any way necessary? The relationships are already described via has_one and belongs_to.

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