From ac2bdd1dd31c8b89578ae7f490a898838b9ef6e0 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Fri, 10 Sep 2010 09:47:50 -0700
Subject: adding an offset node

---
 lib/arel/nodes.rb                  |  1 +
 lib/arel/nodes/offset.rb           | 11 +++++++++++
 lib/arel/nodes/select_statement.rb |  3 ++-
 lib/arel/select_manager.rb         |  5 +++++
 lib/arel/visitors/to_sql.rb        |  5 +++++
 5 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 lib/arel/nodes/offset.rb

(limited to 'lib')

diff --git a/lib/arel/nodes.rb b/lib/arel/nodes.rb
index 2894deab57..89e28f138c 100644
--- a/lib/arel/nodes.rb
+++ b/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'
diff --git a/lib/arel/nodes/offset.rb b/lib/arel/nodes/offset.rb
new file mode 100644
index 0000000000..baa4068d93
--- /dev/null
+++ b/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
diff --git a/lib/arel/nodes/select_statement.rb b/lib/arel/nodes/select_statement.rb
index a96c02a545..6272fd126d 100644
--- a/lib/arel/nodes/select_statement.rb
+++ b/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
diff --git a/lib/arel/select_manager.rb b/lib/arel/select_manager.rb
index 569b631c7f..ce749c4977 100644
--- a/lib/arel/select_manager.rb
+++ b/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
diff --git a/lib/arel/visitors/to_sql.rb b/lib/arel/visitors/to_sql.rb
index 25b7f005ea..d45253abd5 100644
--- a/lib/arel/visitors/to_sql.rb
+++ b/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
-- 
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