Index: issue_nested_set.rb
===================================================================
--- issue_nested_set.rb	(revision 16557)
+++ issue_nested_set.rb	(working copy)
@@ -54,11 +54,13 @@
         self.root_id = parent.root_id
         self.lft = target_lft
         self.rgt = lft + 1
-        self.class.where(:root_id => root_id).where("lft >= ? OR rgt >= ?", lft, lft).update_all([
+        get_update {
+        self.class.reorder('lft desc').where(:root_id => root_id).where("lft >= ? OR rgt >= ?", lft, lft).update_all([
           "lft = CASE WHEN lft >= :lft THEN lft + 2 ELSE lft END, " +
           "rgt = CASE WHEN rgt >= :lft THEN rgt + 2 ELSE rgt END",
           {:lft => lft}
         ])
+        }
       end
 
       def add_as_root
@@ -84,7 +86,7 @@
         if parent
           previous_root_id = root_id
           self.root_id = parent.root_id
-          
+
           lft_after_move = target_lft
           self.class.where(:root_id => parent.root_id).update_all([
             "lft = CASE WHEN lft >= :lft THEN lft + :shift ELSE lft END, " +
@@ -91,12 +93,12 @@
             "rgt = CASE WHEN rgt >= :lft THEN rgt + :shift ELSE rgt END",
             {:lft => lft_after_move, :shift => (rgt - lft + 1)}
           ])
-    
+
           self.class.where(:root_id => previous_root_id).update_all([
             "root_id = :root_id, lft = lft + :shift, rgt = rgt + :shift",
             {:root_id => parent.root_id, :shift => lft_after_move - lft}
           ])
-    
+
           self.lft, self.rgt = lft_after_move, (rgt - lft + lft_after_move)
           parent.send :reload_nested_set_values
         end
@@ -105,7 +107,7 @@
       def remove_from_nested_set
         self.class.where(:root_id => root_id).where("lft >= ? AND rgt <= ?", lft, rgt).
           update_all(["root_id = :id, lft = lft - :shift, rgt = rgt - :shift", {:id => id, :shift => lft - 1}])
-    
+
         self.class.where(:root_id => root_id).update_all([
           "lft = CASE WHEN lft >= :lft THEN lft - :shift ELSE lft END, " +
           "rgt = CASE WHEN rgt >= :lft THEN rgt - :shift ELSE rgt END",
@@ -123,11 +125,13 @@
         children.each {|c| c.send :destroy_without_nested_set_update}
         reload
         unless @without_nested_set_update
-          self.class.where(:root_id => root_id).where("lft > ? OR rgt > ?", lft, lft).update_all([
+          get_update {
+          self.class.reorder('lft asc').where(:root_id => root_id).where("lft > ? OR rgt > ?", lft, lft).update_all([
             "lft = CASE WHEN lft > :lft THEN lft - :shift ELSE lft END, " +
             "rgt = CASE WHEN rgt > :lft THEN rgt - :shift ELSE rgt END",
             {:lft => lft, :shift => rgt - lft + 1}
           ])
+          }
         end
       end
 
@@ -148,7 +152,43 @@
         new_record? || !is_or_is_ancestor_of?(issue)
       end
 
-      def lock_nested_set
+      def get_update(&block)
+        retry_count = 0
+        begin
+          yield
+        rescue ActiveRecord::StatementInvalid => error
+          raise unless error.message =~ /[Dd]eadlock|Lock wait timeout exceeded|[Dd]uplicate/
+          raise unless retry_count < 20
+          retry_count += 1
+          if error.message =~ /[Dd]uplicate/
+            puts "Duplicate retry ##{retry_count} thread: #{Thread.current.object_id}"
+          else
+            puts "Deadlock detected on update, restarting transaction retry ##{retry_count} thread: #{Thread.current.object_id}"
+          end
+          sleep(rand(retry_count)*0.5)
+          retry
+        end
+      end
+
+      def get_lock_with_retry(&block)
+        retry_count = 0
+        begin
+          yield
+        rescue ActiveRecord::StatementInvalid => error
+          raise unless error.message =~ /[Dd]eadlock|Lock wait timeout exceeded/
+          raise unless retry_count < 20
+          retry_count += 1
+          puts "Deadlock detected on getting lock, restarting transaction retry ##{retry_count} thread: #{Thread.current.object_id}"
+          sleep(rand(retry_count)*0.5)
+          retry
+        end
+      end
+
+       def lock_nested_set
+        get_lock_with_retry { get_lock }
+      end
+
+      def get_lock
         if self.class.connection.adapter_name =~ /sqlserver/i
           lock = "WITH (ROWLOCK HOLDLOCK UPDLOCK)"
           # Custom lock for SQLServer
@@ -158,7 +198,8 @@
           self.class.reorder(:id).where(:root_id => sets_to_lock).lock(lock).ids
         else
           sets_to_lock = [id, parent_id].compact
-          self.class.reorder(:id).where("root_id IN (SELECT root_id FROM #{self.class.table_name} WHERE id IN (?))", sets_to_lock).lock.ids
+          #self.class.reorder(:id).where("root_id IN (SELECT root_id FROM #{self.class.table_name} WHERE id IN (?))", sets_to_lock).lock.ids
+          self.class.connection.execute(self.class.reorder(:id).where(:root_id => self.class.where(:id => sets_to_lock).select(:root_id)).lock.to_sql)
         end
       end