Handle rank joins on subquery

Author: causztic

lib/pg_search/scope_options.rb

@@ -79,10 +79,15 @@ def increment_counter
     delegate :connection, :quoted_table_name, to: :model
 
     def subquery
-      model
-        .unscoped
-        .select("#{primary_key} AS pg_search_id")
-        .select("#{rank} AS rank")
+      query = model.unscoped
+      
+      if composite_primary_key?
+        query = query.select(model.primary_key.map.with_index(1) { |part, index| "#{quoted_column_name(part)} AS pg_search_id_#{index}" })
+      else
+        query = query.select("#{primary_key} AS pg_search_id")  
+      end
+
+      query.select("#{rank} AS rank")
         .joins(subquery_join)
         .where(conditions)
         .limit(nil)
@@ -101,11 +106,10 @@ def order_within_rank
     end
 
     def primary_key
-      if model.primary_key.is_a?(Array)
-        model.primary_key.map { |part| "#{quoted_table_name}.#{connection.quote_column_name(part)}" }
-                         .join(',')
+      if composite_primary_key?
+        model.primary_key.map { |part| quoted_column_name(part) }.join(',')
       else
-        "#{quoted_table_name}.#{connection.quote_column_name(model.primary_key)}"
+        quoted_column_name(model.primary_key)
       end
     end
 
@@ -147,7 +151,14 @@ def rank
     end
 
     def rank_join(rank_table_alias)
-      "INNER JOIN (#{subquery.to_sql}) AS #{rank_table_alias} ON #{primary_key} = #{rank_table_alias}.pg_search_id"
+      join_condition = if composite_primary_key?
+        model.primary_key.map.with_index(1) { |part, index| "#{quoted_column_name(part)} = #{rank_table_alias}.pg_search_id_#{index}" }
+          .join(" AND ")
+      else
+        "#{primary_key} = #{rank_table_alias}.pg_search_id"
+      end
+
+      "INNER JOIN (#{subquery.to_sql}) AS #{rank_table_alias} ON #{join_condition}"
     end
 
     def include_table_aliasing_for_rank(scope)
@@ -157,5 +168,17 @@ def include_table_aliasing_for_rank(scope)
         new_scope.instance_eval { extend PgSearchRankTableAliasing }
       end
     end
+
+    def composite_primary_key?
+      model.primary_key.is_a?(Array)
+    end
+
+    def composite_primary_key_length
+      model.primary_key.length
+    end
+
+    def quoted_column_name(column)
+      "#{quoted_table_name}.#{connection.quote_column_name(column)}"
+    end
   end
 end

spec/integration/composite_primary_key_spec.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+describe "composite_primary_key" do
+  with_model :CompositePrimaryKeyModel do
+    table primary_key: [:prefix, :postfix] do |t|
+      t.string :prefix
+      t.string :postfix
+      t.string :name
+    end
+
+    model do
+      include PgSearch::Model
+      self.primary_key = [:prefix, :postfix]
+      pg_search_scope :search_name, against: :name
+    end
+  end
+
+  before { CompositePrimaryKeyModel.create!(id: ["prefix", "postfix"], name: "bar") }
+  let!(:record_1) { CompositePrimaryKeyModel.create!(id: ["prefix_2", "postfix_2"], name: "foo") }
+
+  it "searches without any issues" do
+    expect(CompositePrimaryKeyModel.search_name("foo")).to eq([record_1])
+  end
+end