From d86e20ccbea226bb6e42da508bc040fd03ab473f Mon Sep 17 00:00:00 2001
From: Tamir Duberstein <tamird@squareup.com>
Date: Mon, 23 Feb 2015 09:58:22 -0800
Subject: Special limited delete handling in MSSQL

Refernce:
https://technet.microsoft.com/en-us/library/ms175486%28v=sql.105%29.aspx
---
 lib/arel/visitors/mssql.rb  | 17 +++++++++++++++++
 lib/arel/visitors/to_sql.rb |  4 ++--
 test/visitors/test_mssql.rb |  9 +++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)

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 6084f5746c..ba176a552c 100644
--- a/lib/arel/visitors/to_sql.rb
+++ b/lib/arel/visitors/to_sql.rb
@@ -74,10 +74,10 @@ 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 "
+          collector << ' WHERE '
           collector = inject_join o.wheres, collector, AND
         end
 
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)
-- 
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