Re:GitHub's online schema migration for MySQL
by paulryanrogers on Thursday May 03, 2018 @09:05AM
(#16985585)
There are some techniques for mitigating those, such as adding new columns as nullable without a default.
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Re:GitHub's online schema migration for MySQL
by idunno246 on Thursday May 03, 2018 @12:39PM
(#16987495)
Right, adding a column with a default means the alter takes time while holding that lock and nothing can be read/written so is generally unsafe for big tables, but it doesn’t help if the alter can’t acquire the lock in the first place