#3854 initialize use_write_locks = false refs[t:3854]

git-svn-id: file:///svn/mysql/tokudb-engine/tokudb-engine@33833 c7de825b-a66e-492c-adef-691d508d4ae1

storage/tokudb/ha_tokudb.cc

@@ -1238,6 +1238,7 @@ ha_tokudb::ha_tokudb(handlerton * hton, TABLE_SHARE * table_arg):handler(hton, t
     }
     num_DBs_locked_in_bulk = false;
     lock_count = 0;
+    use_write_locks = false;
 }
 
 //

storage/tokudb/ha_tokudb.h

@@ -235,7 +235,9 @@ class ha_tokudb : public handler {
     //
     DB_TXN *transaction;
     bool is_fast_alter_running;
-    bool use_write_locks;
+
+    // external_lock will set this true for read operations that will be closely followed by write operations.
+    bool use_write_locks; // use write locks for reads
 
     //
     // instance of cursor being used for init_xxx and rnd_xxx functions