2. Execution of an update query

• redo log
  • a technique called WAL (write-ahead logging), to ensure MySQL can achieve crash-safe
  • changes that did not finish updating the data files before an unexpected shutdown are replayed when the server is up again
  • represented by two files ib_logfile0 and ib_logfile1 on disk, writes in a circular fashion
  • only available for InnoDB storage engine
  • See https://dev.mysql.com/doc/refman/5.7/en/innodb-redo-log.html
• binlog
  • useful for replication from master to slave & data recovery point-in-time
  • available since MyISAM storage engine
  • See https://dev.mysql.com/doc/internals/en/binary-log-overview.html