root@db1115.eqiad.wmnet[zarcillo]> set session binlog_format="ROW" -> ; Query OK, 0 rows affected (0.000 sec) root@db1115.eqiad.wmnet[zarcillo]> update masters set instance = (select name from instances where server = 'db1138.eqiad.wmnet' and port=3306) where section = 's4' and dc = 'eqiad' limit 1; Query OK, 1 row affected (0.001 sec) Rows matched: 1 Changed: 1 Warnings: 0