adding an offset node

lib/arel/nodes.rb

@@ -8,6 +8,7 @@ require 'arel/nodes/lock'
 require 'arel/nodes/function'
 require 'arel/nodes/count'
 require 'arel/nodes/values'
+require 'arel/nodes/offset'
 require 'arel/nodes/sum'
 require 'arel/nodes/max'
 require 'arel/nodes/avg'

lib/arel/nodes/offset.rb

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

lib/arel/nodes/select_statement.rb

@@ -2,13 +2,14 @@ module Arel
   module Nodes
     class SelectStatement
       attr_reader :cores
-      attr_accessor :limit, :orders, :lock
+      attr_accessor :limit, :orders, :lock, :offset
 
       def initialize cores = [SelectCore.new]
         @cores  = cores
         @orders = []
         @limit  = nil
         @lock   = nil
+        @offset = nil
       end
 
       def initialize_copy other

lib/arel/select_manager.rb

@@ -12,6 +12,11 @@ module Arel
       @head.limit
     end
 
+    def skip amount
+      @head.offset = Nodes::Offset.new(amount)
+      self
+    end
+
     def where_clauses
       warn "where_clauses is deprecated" if $VERBOSE
       to_sql = Visitors::ToSql.new @engine

lib/arel/visitors/to_sql.rb

@@ -52,6 +52,7 @@ module Arel
           o.cores.map { |x| visit x }.join,
           ("ORDER BY #{o.orders.map { |x| visit x }.join(', ')}" unless o.orders.empty?),
           ("LIMIT #{o.limit}" if o.limit),
+          (visit(o.offset) if o.offset),
           (visit(o.lock) if o.lock),
         ].compact.join ' '
       end
@@ -70,6 +71,10 @@ module Arel
         "HAVING #{visit o.expr}"
       end
 
+      def visit_Arel_Nodes_Offset o
+        "OFFSET #{visit o.value}"
+      end
+
       # FIXME: this does nothing on SQLLite3, but should do things on other
       # databases.
       def visit_Arel_Nodes_Lock o

spec/arel/select_manager_spec.rb

@@ -26,6 +26,21 @@ module Arel
   end
 
   describe 'select manager' do
+    describe 'skip' do
+      it 'should add an offset' do
+        table   = Table.new :users
+        mgr = table.from table
+        mgr.skip 10
+        mgr.to_sql.should be_like %{ SELECT FROM "users" OFFSET 10 }
+      end
+
+      it 'should chain' do
+        table   = Table.new :users
+        mgr = table.from table
+        mgr.skip(10).to_sql.should be_like %{ SELECT FROM "users" OFFSET 10 }
+      end
+    end
+
     describe 'taken' do
       it 'should return limit' do
         table   = Table.new :users