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POArel, Joins and Rails Queries
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  1. POArel, Joins and Rails Queries
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    copied!<p>I've been stuck on a problem recently for a little while and found my way to Arel which looks like it should allow me to do OR's in my queries.</p> <p>As a starting point I needed to convert an existing Rails 3 query to Arel and that's where I've run into problems.</p> <p>The following scope and query works as I would expect it to. It gives me the requests associated with a particular user's ads.</p> <pre><code>#in the Request class scope :responder, lambda { |user| joins(:ad).where(:ads =&gt; { :user_id =&gt; user }) } Request.responder(303).to_sql =&gt; "SELECT \"requests\".* FROM \"requests\" INNER JOIN \"ads\" ON \"ads\".\"id\" = \"requests\".\"ad_id\" WHERE (\"ads\".\"user_id\" = 303)" </code></pre> <p>According to doco on the Arel github page and Railscast 215 I should be able to do something like the following to replicate the query with Arel</p> <pre><code> requests = Request.arel_table ads = Ad.arel_table where(requests.join(ads).on(ads[:id].eq(requests[:ad_id]))) </code></pre> <p>This results in an error</p> <pre><code>TypeError: Cannot visit Arel::SelectManager </code></pre> <p>I can do the following in the console though</p> <pre><code>r = Request.arel_table a = Ad.arel_table r.join(a).to_sql =&gt; "SELECT FROM \"requests\" INNER JOIN \"ads\" " </code></pre> <p>So it looks like it's forming the SQL request, however when you put that in a where</p> <pre><code>Request.where(r.join(a)).to_sql </code></pre> <p>I get the following</p> <pre><code>TypeError: Cannot visit Arel::SelectManager.... </code></pre> <p>I've tried doing other Arel actions within the where and it works (e.g.)</p> <pre><code>Request.where(r[:status].eq(nil)).to_sql =&gt; "SELECT \"requests\".* FROM \"requests\" WHERE (\"requests\".\"status\" IS NULL)" </code></pre> <p>This is a little beyond my growing rails/ruby knowledge. Any ideas?</p> <p>Thanks in advance.</p>
 

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