add locking support for postgres

3 files changed, 22 insertions, 0 deletions

diff --git a/Manifest.txt b/Manifest.txt
index a14b9aad2b..0c74e6932e 100644
--- a/Manifest.txt
+++ b/Manifest.txt
@@ -102,4 +102,5 @@ spec/table_spec.rb
 spec/update_manager_spec.rb
 spec/visitors/join_sql_spec.rb
 spec/visitors/oracle_spec.rb
+spec/visitors/postgres_spec.rb
 spec/visitors/to_sql_spec.rb
diff --git a/lib/arel/visitors/postgresql.rb b/lib/arel/visitors/postgresql.rb
index 5e03f40984..553ee91bf9 100644
--- a/lib/arel/visitors/postgresql.rb
+++ b/lib/arel/visitors/postgresql.rb
@@ -2,6 +2,10 @@ module Arel
   module Visitors
     class PostgreSQL < Arel::Visitors::ToSql
       private
+      def visit_Arel_Nodes_Lock o
+        "FOR UPDATE"
+      end
+
       def visit_Arel_Nodes_SelectStatement o
         if !o.orders.empty? && using_distinct_on?(o)
           subquery        = o.dup
diff --git a/spec/visitors/postgres_spec.rb b/spec/visitors/postgres_spec.rb
new file mode 100644
index 0000000000..b5174a4c04
--- /dev/null
+++ b/spec/visitors/postgres_spec.rb
@@ -0,0 +1,17 @@
+require 'spec_helper'
+
+module Arel
+  module Visitors
+    describe 'the postgres visitor' do
+      before do
+        @visitor = PostgreSQL.new Table.engine
+      end
+
+      it 'should produce a lock value' do
+        @visitor.accept(Nodes::Lock.new).should be_like %{
+          FOR UPDATE
+        }
+      end
+    end
+  end
+end