1 files changed, 44 insertions, 0 deletions
diff --git a/activerecord/lib/arel/nodes/function.rb b/activerecord/lib/arel/nodes/function.rb
new file mode 100644
index 0000000000..0a439b39f5
--- /dev/null
+++ b/activerecord/lib/arel/nodes/function.rb
@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+module Arel # :nodoc: all
+  module Nodes
+    class Function < Arel::Nodes::NodeExpression
+      include Arel::WindowPredications
+      attr_accessor :expressions, :alias, :distinct
+
+      def initialize(expr, aliaz = nil)
+        super()
+        @expressions = expr
+        @alias       = aliaz && SqlLiteral.new(aliaz)
+        @distinct    = false
+      end
+
+      def as(aliaz)
+        self.alias = SqlLiteral.new(aliaz)
+        self
+      end
+
+      def hash
+        [@expressions, @alias, @distinct].hash
+      end
+
+      def eql?(other)
+        self.class == other.class &&
+          self.expressions == other.expressions &&
+          self.alias == other.alias &&
+          self.distinct == other.distinct
+      end
+      alias :== :eql?
+    end
+
+    %w{
+      Sum
+      Exists
+      Max
+      Min
+      Avg
+    }.each do |name|
+      const_set(name, Class.new(Function))
+    end
+  end
+end