ALTER TABLE without locking the table?

Question

When doing an ALTER TABLE statement in MySQL, the whole table is read-locked (allowing concurrent reads, but prohibiting concurrent writes) for the duration of the statement

Answer 1

See Facebook's online schema change tool.

http://www.facebook.com/notes/mysql-at-facebook/online-schema-change-for-mysql/430801045932

Not for the faint of heart; but it will do the job.