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PORails: Postgresql where with multiple conditions with join (polymorphic)
 

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  1. PORails: Postgresql where with multiple conditions with join (polymorphic)
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    <p>Hi guys here is my code:</p> <pre><code>class Tailor &lt; ActiveRecord::Base has_many :tailor_items has_many :order_items [:collars, :sexes, :sleeves].each do |attribute| has_many attribute, through: :tailor_items, source: :item, source_type: attribute.to_s.classify end end class TailorItem &lt; ActiveRecord::Base belongs_to :tailor belongs_to :item, polymorphic: true end class Collar &lt; ActiveRecord::Base end </code></pre> <p>What I need to do is this: For a given shirt I need to select a tailor. A shirt can have a collar, male/female or a certain type of sleeve. Some tailors can make all collars but only a few sleeves, others can make only male stuff, etc. The priority doesnt matter for this example. The idea is that I end up with 1 tailor.</p> <p>I tried this:</p> <pre><code>tailors = Tailor.joins(:tailor_items).where("(item_id = ? and item_type = ?)",1,"Collar") if tailors.count &gt; 1 tailors.where("(item_id = ? and item_type = ?)",2,"Sleeve") if tailors.count &gt; 1 # and so forth. end end </code></pre> <p>But I never get a row back. If I say:</p> <pre><code>Tailor.find(1).tailor_items </code></pre> <p>I get two results (sudo code for simplicity)</p> <pre><code>&lt;id: 1, item_type: "Collar"&gt;&lt;id:2, item_type:"Sleeve"&gt; </code></pre> <p>and for second tailor:</p> <pre><code>Tailor.find(2).tailor_items </code></pre> <p>I get two results (sudo code for simplicity)</p> <pre><code>&lt;id: 1, item_type: "Collar"&gt;&lt;id:3, item_type:"Sleeve"&gt; </code></pre> <p>but when I try to chain them in the query its no worky... Not even if I put it all in one where:</p> <pre><code>Tailor.where("(item_id = 1 and item_type = 'Collar') and (item_id = 2 and item_type = 'Sleeve')") </code></pre> <p>I still get 0 results.</p> <pre><code>Tailor.where("item_id = 1 and item_type = 'Collar'") returns: Tailor #1 Tailor.where("item_id = 2 and item_type = 'Sleeve'") returns: Tailor #1 </code></pre> <p>but together they return nothing.</p> <pre><code>Tailor Load (0.0ms) SELECT "tailors".* FROM "tailors" INNER JOIN "tailor_items" ON "tailor_items"."tailor_id" = "tailors"."id" WHERE ((tailo r_items.item_id = 1 and tailor_items.item_type = 'Collar') and (tailor_items.ite m_id = 2 and tailor_items.item_type = 'Sleeve')) </code></pre> <p>I am confused..</p> <p>Thanks for your help.</p> <p>I run: Win XP Postgresql Rails 3.2.2</p> <p>PS: The only thing missing to make this complete after a polymorphic join is a bit of XML. :P Otherwise its just not enterprise-y enough..</p> <p>EDIT: Implementing Rob di Marcos scope, I get this SQL:</p> <pre><code>SELECT "tailors".* FROM "tailors" WHERE (EXISTS(SELECT * FROM tailor_items WHERE tailor_items.item_id = 1 and tailor_items.item_type = 'Collar')) AND (exists(select * from tailor_items where tailor_items.item_id = 2 and tailor_items.item_type = 'Sleeve')) </code></pre> <p>This returns 2 tailors instead of only tailor 1 who can do both (while tailor 2 cant do sleeve #2)</p>
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