It looks like my production upgrade is going to take hours, mostly due to scripts/migrate20071206-WidenSizeColumns.pl:
ALTER TABLE mboxgroup1.mail_item MODIFY COLUMN size BIGINT UNSIGNED NOT NULL ... ALTER TABLE mboxgroup100.mail_item MODIFY COLUMN size BIGINT UNSIGNED NOT NULL
Are there any my.cnf options that might speed this up? My largest mail_item.idb is 260M, with 343,000 rows.
Could I perhaps perform these changes on a running 4.5.10 system without downtime? A BIGINT column should be backwards compatible with INT, shouldn't it?
Or maybe consider (danger!!!) skipping this script? I don't plan to allow items > 2GB any time soon, and it looks like the issue isn't fixed anyway: (Bug #22362) MailItem size must be long instead of int