1 files changed, 6 insertions, 0 deletions
diff --git a/sql/sql_class.h b/sql/sql_class.h
index 67018c0299a..42e6aea2aa8 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -5776,6 +5776,12 @@ public:
   uint  sum_func_count;   
   uint  hidden_field_count;
   uint	group_parts,group_length,group_null_parts;
+
+  /*
+    If we're doing a GROUP BY operation, shows which one is used:
+    true  TemporaryTableWithPartialSums algorithm (see end_update()).
+    false OrderedGroupBy algorithm (see end_write_group()).
+  */
   uint	quick_group;
   /**
     Enabled when we have atleast one outer_sum_func. Needed when used