GH-139: some aggregations lacked DISTINCT emission

2 files changed, 43 insertions, 4 deletions

diff --git a/lib/arel/visitors/to_sql.rb b/lib/arel/visitors/to_sql.rb
index a350daa3da..9c76772ef8 100644
--- a/lib/arel/visitors/to_sql.rb
+++ b/lib/arel/visitors/to_sql.rb
@@ -283,22 +283,22 @@ key on UpdateManager using UpdateManager#key=
       end
 
       def visit_Arel_Nodes_Sum o
-        "SUM(#{o.expressions.map { |x|
+        "SUM(#{o.distinct ? 'DISTINCT ' : ''}#{o.expressions.map { |x|
           visit x }.join(', ')})#{o.alias ? " AS #{visit o.alias}" : ''}"
       end
 
       def visit_Arel_Nodes_Max o
-        "MAX(#{o.expressions.map { |x|
+        "MAX(#{o.distinct ? 'DISTINCT ' : ''}#{o.expressions.map { |x|
           visit x }.join(', ')})#{o.alias ? " AS #{visit o.alias}" : ''}"
       end
 
       def visit_Arel_Nodes_Min o
-        "MIN(#{o.expressions.map { |x|
+        "MIN(#{o.distinct ? 'DISTINCT ' : ''}#{o.expressions.map { |x|
           visit x }.join(', ')})#{o.alias ? " AS #{visit o.alias}" : ''}"
       end
 
       def visit_Arel_Nodes_Avg o
-        "AVG(#{o.expressions.map { |x|
+        "AVG(#{o.distinct ? 'DISTINCT ' : ''}#{o.expressions.map { |x|
           visit x }.join(', ')})#{o.alias ? " AS #{visit o.alias}" : ''}"
       end
 
diff --git a/test/visitors/test_to_sql.rb b/test/visitors/test_to_sql.rb
index 1caedacd45..dfe1d49a4e 100644
--- a/test/visitors/test_to_sql.rb
+++ b/test/visitors/test_to_sql.rb
@@ -48,6 +48,45 @@ module Arel
         sql.must_be_like %{ omg(*) = 2 }
       end
 
+      it 'should visit built-in functions' do
+        function = Nodes::Count.new([Arel.star])
+        assert_equal 'COUNT(*)', @visitor.accept(function)
+
+        function = Nodes::Sum.new([Arel.star])
+        assert_equal 'SUM(*)', @visitor.accept(function)
+
+        function = Nodes::Max.new([Arel.star])
+        assert_equal 'MAX(*)', @visitor.accept(function)
+
+        function = Nodes::Min.new([Arel.star])
+        assert_equal 'MIN(*)', @visitor.accept(function)
+
+        function = Nodes::Avg.new([Arel.star])
+        assert_equal 'AVG(*)', @visitor.accept(function)
+      end
+
+      it 'should visit built-in functions operating on distinct values' do
+        function = Nodes::Count.new([Arel.star])
+        function.distinct = true
+        assert_equal 'COUNT(DISTINCT *)', @visitor.accept(function)
+
+        function = Nodes::Sum.new([Arel.star])
+        function.distinct = true
+        assert_equal 'SUM(DISTINCT *)', @visitor.accept(function)
+
+        function = Nodes::Max.new([Arel.star])
+        function.distinct = true
+        assert_equal 'MAX(DISTINCT *)', @visitor.accept(function)
+
+        function = Nodes::Min.new([Arel.star])
+        function.distinct = true
+        assert_equal 'MIN(DISTINCT *)', @visitor.accept(function)
+
+        function = Nodes::Avg.new([Arel.star])
+        function.distinct = true
+        assert_equal 'AVG(DISTINCT *)', @visitor.accept(function)
+      end
+
       it 'works with lists' do
         function = Nodes::NamedFunction.new('omg', [Arel.star, Arel.star])
         assert_equal 'omg(*, *)', @visitor.accept(function)