adding having nodes

lib/arel/nodes.rb

@@ -7,6 +7,7 @@ require 'arel/nodes/in'
 require 'arel/nodes/count'
 require 'arel/nodes/sum'
 require 'arel/nodes/max'
+require 'arel/nodes/having'
 require 'arel/nodes/sql_literal'
 require 'arel/nodes/select_core'
 require 'arel/nodes/select_statement'

lib/arel/nodes/having.rb

@@ -0,0 +1,11 @@
+module Arel
+  module Nodes
+    class Having
+      attr_accessor :expr
+
+      def initialize expr
+        @expr = expr
+      end
+    end
+  end
+end

lib/arel/nodes/select_core.rb

@@ -2,12 +2,14 @@ module Arel
   module Nodes
     class SelectCore
       attr_reader :froms, :projections, :wheres, :groups
+      attr_accessor :having
 
       def initialize
         @froms       = []
         @projections = []
         @wheres      = []
         @groups      = []
+        @having      = nil
       end
 
       def initialize_copy other
@@ -16,6 +18,7 @@ module Arel
         @projections = @projections.clone
         @wheres      = @wheres.clone
         @group       = @groups.clone
+        @having      = @having.clone if @having
       end
     end
   end

lib/arel/select_manager.rb

@@ -40,6 +40,11 @@ module Arel
       end
     end
 
+    def having expr
+      @ctx.having = Nodes::Having.new(expr)
+      self
+    end
+
     def project *projections
       # FIXME: converting these to SQLLiterals is probably not good, but
       # rails tests require it.

lib/arel/table.rb

@@ -61,6 +61,10 @@ module Arel
       tm.take amount
     end
 
+    def having expr
+      tm.having expr
+    end
+
     def columns
       @columns ||= @engine.connection.columns(@name, "#{@name} Columns").map do |column|
         Attributes.for(column).new self, column.name, column

lib/arel/visitors/to_sql.rb

@@ -57,10 +57,15 @@ module Arel
           "SELECT #{o.projections.map { |x| visit x }.join ', '}",
           ("FROM #{o.froms.map { |x| visit x }.join ', ' }" unless o.froms.empty?),
           ("WHERE #{o.wheres.map { |x| visit x }.join ' AND ' }" unless o.wheres.empty?),
-          ("GROUP BY #{o.groups.map { |x| visit x }.join ', ' }" unless o.groups.empty?)
+          ("GROUP BY #{o.groups.map { |x| visit x }.join ', ' }" unless o.groups.empty?),
+          (visit(o.having) if o.having),
         ].compact.join ' '
       end
 
+      def visit_Arel_Nodes_Having o
+        "HAVING #{visit o.expr}"
+      end
+
       def visit_Arel_Nodes_Group o
         visit o.expr
       end

spec/arel/table_spec.rb

@@ -6,6 +6,15 @@ module Arel
       @relation = Table.new(:users)
     end
 
+    describe 'having' do
+      it 'adds a having clause' do
+        mgr = @relation.having @relation[:id].eq(10)
+        mgr.to_sql.should be_like %{
+         SELECT FROM "users" HAVING "users"."id" = 10
+        }
+      end
+    end
+
     describe 'backwards compat' do
       describe 'joins' do
         it 'returns nil' do