added aggregations

1 files changed, 21 insertions, 0 deletions

diff --git a/lib/active_relation/primitives/aggregation.rb b/lib/active_relation/primitives/aggregation.rb
new file mode 100644
index 0000000000..20fdcf46c5
--- /dev/null
+++ b/lib/active_relation/primitives/aggregation.rb
@@ -0,0 +1,21 @@
+module ActiveRelation
+  module Primitives
+    class Aggregation
+      include SqlBuilder
+  
+      attr_reader :attribute, :function_sql
+      
+      def initialize(attribute, function_sql)
+        @attribute, @function_sql = attribute, function_sql
+      end
+  
+      def to_sql(options = {})
+        "#{function_sql}(@attribute.to_sql)"
+      end
+      
+      def ==(other)
+        self.class == other.class and attribute == other.attribute and function_sql == other.function_sql
+      end
+    end
+  end
+end
\ No newline at end of file