Thank you! This looks promising. One follow-up question, even though I think I know the answer.
When I go to ACP -> Maintenance -> Search Index, I don't have the option to delete anything. As I've said, it seems to be "stuck" thinking that whatever I started previously is still running. This is what my screen looks like:
My assumption would be to proceed with your steps while skipping this, since I can't perform that task at the moment?
And, actually, I'll ask a second question here too, that's barely tangentially related. I
found a link on Bluehost's Knowledge Base that was tangentially related to my issue. Basically, I stumbled across this because when I originally submitted the search index job, and when I pressed the "Submit" button in the screenshot above one time, the job eventually dies while trying to do the ALTER TABLE command on phpbb3_posts (see a previous post for the whole error). When that happens, anything related to the posts table - like view a thread - goes to heck in a handbasket. "Repair Database" seemed to be the place to go for that, but it was failing from Bluehost's console. Sadly, it also failed when I tried from within phpMyAdmin. Eventually - I'm guessing about 24 hours or so - it'll clear up and let me perform Repair Database either way.
In that link, it discusses issues with using the InnoDB engine - and that is what all the phpbb3 tables are using. Is it worthwhile to switch the tables from InnoDB to MyISAM, which is what my phpbb v2 tables use? I've done some poking around, and it looks like the biggest differences are that InnoDB supports row-level locking while MyISAM uses table locking; and InnoDB supports Transactions, and MyISAM does not. That last one seems to be the bigger deal to me, as what I've read says that means InnoDB supports Commit and Rollback, and MyISAM does not. It may not matter, though, if there are no "Rollback" commands ever issued via the phpbb3 code.
Since I'm doing ALTER TABLE commands on all the tables, is it worthwhile to also switch to MyISAM? Or will I lose too much valuable functionality with the loss of Commit / Rollback?
That... turned out longer than I wanted. Ugh. Thanks!