I've written two separate posts about the MySQL 5.6 temporal column
format change, but I haven't yet addressed the problem with the
way this upgrade was implemented. Essentially, the problem is
that the implicit format upgrade causes a write-blocking full
table rebuild the first time you run ALTER TABLE
after upgrading, even if the ALTER TABLE command is
an online DDL operation that normally doesn't block writes.
This behavior is well intentioned, but harmful. The intent is for
the server to tack on a seemingly innocuous column format upgrade
to my existing ALTER TABLE command, but when it
changes my DDL from non-blocking …