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POis there a way to eager load polymorphic association's associations?
 

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  1. POis there a way to eager load polymorphic association's associations?
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    <p>artists have many activities (basically a cache of interactions between users):</p> <pre><code>class Activity &lt; ActiveRecord::Base belongs_to :receiver, :class_name =&gt; 'Artist', :foreign_key =&gt; :receiver_id #owns the stuff done "TO" him belongs_to :link, :polymorphic =&gt; true belongs_to :creator, :class_name =&gt; 'Artist', :foreign_key =&gt; :creator_id #person who initiated the activity end </code></pre> <p>For example: </p> <pre><code> Activity.create(:receiver_id =&gt; author_id, :creator_id =&gt; artist_id, :link_id =&gt; id, :link_type =&gt; 'ArtRating') </code></pre> <p>I want to create an activity stream page for each artist, consisting of a list of different types of events, ArtRatings (likes, dislikes), Favoriting, Following etc.</p> <p>The controller looks like this:</p> <pre><code>class ActivityStreamController &lt; ApplicationController def index @activities = @artist.activities.includes([:link,:creator,:receiver]).order("id DESC").limit(30) end end </code></pre> <p>The db call correctly eagerly loads the polymorphic link objects:</p> <pre><code> SELECT "activities".* FROM "activities" WHERE (("activities"."receiver_id" = 6 OR "activities"."creator_id" = 6)) ORDER BY id DESC LIMIT 30 ArtRating Load (0.5ms) SELECT "art_ratings".* FROM "art_ratings" WHERE "art_ratings"."id" IN (137, 136, 133, 130, 126, 125, 114, 104, 103, 95, 85, 80, 73, 64) SELECT "follows".* FROM "follows" WHERE "follows"."id" IN (14, 10) SELECT "favorites".* FROM "favorites" WHERE "favorites"."id" IN (25, 16, 14) </code></pre> <p>But when I display each ArtRating, I also need to reference the post title, which belongs to a post. In the view, if I do:</p> <pre><code>activity.link.post </code></pre> <p>It does a separate DB call for each art_rating's post. Is there a way to eagerly load the post as well?</p> <p><strong>UPDATE TO THE QUESTION:</strong></p> <p>If there is no way to achieve eager loading of posts using 'includes' syntax, is there a way to manually do the eager loading query myself and inject it into the @activities object?</p> <p>I see in the DB log: </p> <pre><code>SELECT "art_ratings".* FROM "art_ratings" WHERE "art_ratings"."id" IN (137, 136, 133, 130, 126, 125, 114, 104, 103, 95, 85, 80, 73, 64) </code></pre> <p>Is there a way I can access this list of ids from the @activities object? If so, I could do 2 additional queries, 1 to get the art_ratings.post_id(s) in that list, and another to SELECT all posts IN those list of post_ids. Then somehow inject the 'post' results back into @activities so that it's available as activity.link.post when I iterate through the collection. Possible?</p>
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    1. COany progress here?
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    2. COFrom what I understand, you have a set of models that are supposed to be attached to activities as links and I gather they all share at least one association, which is `post`. Is there maybe enough common ground in these link models to use [Single Table Inheritance](http://apidock.com/rails/ActiveRecord/Base) and put all in one table?
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