Merge pull request #356 from tamird/limited-delete

Limited delete

7 files changed, 47 insertions, 5 deletions

diff --git a/lib/arel/crud.rb b/lib/arel/crud.rb
index 2dfe27445c..d310c7381f 100644
--- a/lib/arel/crud.rb
+++ b/lib/arel/crud.rb
@@ -31,6 +31,7 @@ module Arel
 
     def compile_delete
       dm = DeleteManager.new
+      dm.take @ast.limit.expr if @ast.limit
       dm.wheres = @ctx.wheres
       dm.from @ctx.froms
       dm
diff --git a/lib/arel/delete_manager.rb b/lib/arel/delete_manager.rb
index af33c60740..20e988e01f 100644
--- a/lib/arel/delete_manager.rb
+++ b/lib/arel/delete_manager.rb
@@ -11,6 +11,11 @@ module Arel
       self
     end
 
+    def take limit
+      @ast.limit = Nodes::Limit.new(Nodes.build_quoted(limit)) if limit
+      self
+    end
+
     def wheres= list
       @ast.wheres = list
     end
diff --git a/lib/arel/nodes/delete_statement.rb b/lib/arel/nodes/delete_statement.rb
index 3bac8225ec..8aaf8ca0b6 100644
--- a/lib/arel/nodes/delete_statement.rb
+++ b/lib/arel/nodes/delete_statement.rb
@@ -1,6 +1,8 @@
 module Arel
   module Nodes
     class DeleteStatement < Arel::Nodes::Binary
+      attr_accessor :limit
+
       alias :relation :left
       alias :relation= :left=
       alias :wheres :right
diff --git a/lib/arel/visitors/mssql.rb b/lib/arel/visitors/mssql.rb
index 7c65ad33f2..92362a0c5f 100644
--- a/lib/arel/visitors/mssql.rb
+++ b/lib/arel/visitors/mssql.rb
@@ -66,6 +66,23 @@ module Arel
         end
       end
 
+      def visit_Arel_Nodes_DeleteStatement o, collector
+        collector << 'DELETE '
+        if o.limit
+          collector << 'TOP ('
+          visit o.limit.expr, collector
+          collector << ') '
+        end
+        collector << 'FROM '
+        collector = visit o.relation, collector
+        if o.wheres.any?
+          collector << ' WHERE '
+          inject_join o.wheres, collector, AND
+        else
+          collector
+        end
+      end
+
       def determine_order_by orders, x
         if orders.any?
           orders
diff --git a/lib/arel/visitors/to_sql.rb b/lib/arel/visitors/to_sql.rb
index 7dfa86a575..ba176a552c 100644
--- a/lib/arel/visitors/to_sql.rb
+++ b/lib/arel/visitors/to_sql.rb
@@ -74,14 +74,14 @@ module Arel
       end
 
       def visit_Arel_Nodes_DeleteStatement o, collector
-        collector << "DELETE FROM "
+        collector << 'DELETE FROM '
         collector = visit o.relation, collector
         if o.wheres.any?
-          collector << " WHERE "
-          inject_join o.wheres, collector, AND
-        else
-          collector
+          collector << ' WHERE '
+          collector = inject_join o.wheres, collector, AND
         end
+
+        maybe_visit o.limit, collector
       end
 
       # FIXME: we should probably have a 2-pass visitor for this
diff --git a/test/test_delete_manager.rb b/test/test_delete_manager.rb
index b16b52cb9e..ece2389d88 100644
--- a/test/test_delete_manager.rb
+++ b/test/test_delete_manager.rb
@@ -8,6 +8,14 @@ module Arel
       end
     end
 
+    it 'handles limit properly' do
+      table = Table.new(:users)
+      dm = Arel::DeleteManager.new
+      dm.take 10
+      dm.from table
+      assert_match(/LIMIT 10/, dm.to_sql)
+    end
+
     describe 'from' do
       it 'uses from' do
         table = Table.new(:users)
diff --git a/test/visitors/test_mssql.rb b/test/visitors/test_mssql.rb
index 7574aeb0a2..fe228bce4b 100644
--- a/test/visitors/test_mssql.rb
+++ b/test/visitors/test_mssql.rb
@@ -45,6 +45,15 @@ module Arel
         connection.verify
       end
 
+      it 'should use TOP for limited deletes' do
+        stmt = Nodes::DeleteStatement.new
+        stmt.relation = @table
+        stmt.limit = Nodes::Limit.new(10)
+        sql = compile(stmt)
+
+        sql.must_be_like "DELETE TOP (10) FROM \"users\""
+      end
+
       it 'should go over query ORDER BY if .order()' do
         stmt = Nodes::SelectStatement.new
         stmt.limit = Nodes::Limit.new(10)