From 2579fec805f23903dd6c4f1726198e010f5a9a54 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Mon, 23 Aug 2010 10:14:02 -0700
Subject: adding count nodes

---
 lib/arel/nodes.rb                   |  1 +
 lib/arel/nodes/count.rb             | 12 ++++++++++++
 lib/arel/nodes/sql_literal.rb       |  3 +++
 lib/arel/visitors/to_sql.rb         |  4 ++++
 spec/arel/nodes/sql_literal_spec.rb | 19 +++++++++++++++++++
 5 files changed, 39 insertions(+)
 create mode 100644 lib/arel/nodes/count.rb
 create mode 100644 spec/arel/nodes/sql_literal_spec.rb

diff --git a/lib/arel/nodes.rb b/lib/arel/nodes.rb
index 67568b5fd4..98fc045690 100644
--- a/lib/arel/nodes.rb
+++ b/lib/arel/nodes.rb
@@ -3,6 +3,7 @@ require 'arel/nodes/equality'
 require 'arel/nodes/or'
 
 require 'arel/nodes/in'
+require 'arel/nodes/count'
 require 'arel/nodes/sql_literal'
 require 'arel/nodes/select_core'
 require 'arel/nodes/select_statement'
diff --git a/lib/arel/nodes/count.rb b/lib/arel/nodes/count.rb
new file mode 100644
index 0000000000..b7c4b60948
--- /dev/null
+++ b/lib/arel/nodes/count.rb
@@ -0,0 +1,12 @@
+module Arel
+  module Nodes
+    class Count
+      attr_accessor :expressions, :distinct
+
+      def initialize expr, distinct = false
+        @expressions = expr
+        @distinct    = distinct
+      end
+    end
+  end
+end
diff --git a/lib/arel/nodes/sql_literal.rb b/lib/arel/nodes/sql_literal.rb
index 53ff376071..526d088449 100644
--- a/lib/arel/nodes/sql_literal.rb
+++ b/lib/arel/nodes/sql_literal.rb
@@ -1,6 +1,9 @@
 module Arel
   module Nodes
     class SqlLiteral < String
+      def count distinct = false
+        Count.new [self], distinct
+      end
     end
   end
 end
diff --git a/lib/arel/visitors/to_sql.rb b/lib/arel/visitors/to_sql.rb
index 55ed53177e..05c33ddb8b 100644
--- a/lib/arel/visitors/to_sql.rb
+++ b/lib/arel/visitors/to_sql.rb
@@ -58,6 +58,10 @@ module Arel
         ].compact.join ' '
       end
 
+      def visit_Arel_Nodes_Count o
+        "COUNT(#{o.distinct ? 'DISTINCT ' : ''}#{o.expressions.map { |x| visit x }.join(', ')})"
+      end
+
       def visit_Arel_Nodes_TableAlias o
         "#{visit o.relation} #{quote_table_name o.name}"
       end
diff --git a/spec/arel/nodes/sql_literal_spec.rb b/spec/arel/nodes/sql_literal_spec.rb
new file mode 100644
index 0000000000..390eb708e1
--- /dev/null
+++ b/spec/arel/nodes/sql_literal_spec.rb
@@ -0,0 +1,19 @@
+module Arel
+  module Nodes
+    describe 'sql literal' do
+      describe 'count' do
+        it 'makes a count node' do
+          node = SqlLiteral.new('*').count
+          viz = Visitors::ToSql.new Table.engine
+          viz.accept(node).should be_like %{ COUNT(*) }
+        end
+
+        it 'makes a distinct node' do
+          node = SqlLiteral.new('*').count true
+          viz = Visitors::ToSql.new Table.engine
+          viz.accept(node).should be_like %{ COUNT(DISTINCT *) }
+        end
+      end
+    end
+  end
+end
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