title: Rails PG::UndefinedTable: ERROR: missing FROM-clause entry for table
body: <p>I have models</p>
  
  <pre><code>class Offer &lt; ActiveRecord::Base
    belongs_to :agency
  end
  
  class Agency &lt; ActiveRecord::Base
    has_many :offers
  end
  </code></pre>
  
  <p>When I do such request - everything is OK</p>
  
  <pre><code>@offers = Offer.with_state(:confirmed).
    includes(:destination, :cruise_line, :ship).
    paginate(per_page: 10, page: params[:page]).decorate
  </code></pre>
  
  <p>But I want to select only offers that belong to <code>active</code> agencies (column <code>state</code> from <code>agencies</code> table), so I try to do like this:</p>
  
  <pre><code>@offers = Offer.with_state(:confirmed).
    includes(:destination, :cruise_line, :ship).
    joins(:agency).
    where(agency: {state: 'active'}).
    paginate(per_page: 10, page: params[:page]).decorate
  </code></pre>
  
  <p>Having done this I get error <code>PG::UndefinedTable: ERROR: missing FROM-clause entry for table "agency"</code>. What is wrong with my code?</p>
  
  <p>The query gives me this error and sql:</p>
  
  <pre><code>PG::UndefinedTable: ERROR: missing FROM-clause entry for table "agency" LINE 1: ...id" WHERE ("offers"."state" IN ('confirmed')) AND "agency"."... ^ : 
  SELECT "offers"."id" AS t0_r0, "offers"."name" AS t0_r1, "offers"."destination_id" AS t0_r2, "offers"."cruise_line_id" AS t0_r3, "offers"."ship_id" AS t0_r4, "offers"."departure_date" AS t0_r5, "offers"."departure_port_id" AS t0_r6, "offers"."arrival_date" AS t0_r7, "offers"."arrival_port_id" AS t0_r8, "offers"."flight_price" AS t0_r9, "offers"."bonus" AS t0_r10, "offers"."itinerary" AS t0_r11, "offers"."board_language_id" AS t0_r12, "offers"."agency_landing_page" AS t0_r13, "offers"."benefits" AS t0_r14, "offers"."inner_price" AS t0_r15, "offers"."inner_price_normal" AS t0_r16, "offers"."outer_price" AS t0_r17, "offers"."outer_price_normal" AS t0_r18, "offers"."balcony_price" AS t0_r19, "offers"."balcony_price_normal" AS t0_r20, "offers"."suite_price" AS t0_r21, "offers"."suite_price_normal" AS t0_r22, "offers"."lucky_price" AS t0_r23, "offers"."lucky_price_normal" AS t0_r24, "offers"."valid_from" AS t0_r25, "offers"."valid_till" AS t0_r26, "offers"."created_at" AS t0_r27, "offers"."updated_at" AS t0_r28, "offers"."description" AS t0_r29, "offers"."agency_id" AS t0_r30, "offers"."state" AS t0_r31, "destinations"."id" AS t1_r0, "destinations"."name" AS t1_r1, "destinations"."created_at" AS t1_r2, "destinations"."updated_at" AS t1_r3, "cruise_lines"."id" AS t2_r0, "cruise_lines"."name" AS t2_r1, "cruise_lines"."created_at" AS t2_r2, "cruise_lines"."updated_at" AS t2_r3, "ships"."id" AS t3_r0, "ships"."name" AS t3_r1, "ships"."picture" AS t3_r2, "ships"."cruise_line_id" AS t3_r3, "ships"."created_at" AS t3_r4, "ships"."updated_at" AS t3_r5 
  FROM "offers" 
  INNER JOIN "agencies" ON "agencies"."id" = "offers"."agency_id" 
  LEFT OUTER JOIN "destinations" ON "destinations"."id" = "offers"."destination_id" 
  LEFT OUTER JOIN "cruise_lines" ON "cruise_lines"."id" = "offers"."cruise_line_id" 
  LEFT OUTER JOIN "ships" ON "ships"."id" = "offers"."ship_id" 
  WHERE ("offers"."state" IN ('confirmed')) AND "agency"."state" = 'active' 
  LIMIT 10 OFFSET 0
  </code></pre>