There are also already a bunch of tailored messages in other context:

I looked into this briefly, but I can't find a simple way to show all the current user's database permissions.

That covered everything that looked low-hanging.

Vaguely adjacent:

Now that we are on RDS I can confirm that MySQL also has ONLY_FULL_GROUP_BY enabled by default.

That actually using MySQL official Docker image.

There are only 23 occurrences of the string "GROUP BY" in the codebase, and, from inspection, many obviously do not conflict with ONLY_FULL_GROUP_BY.

Anecdata: locally, using 2 subprocesses went twice as fast (~85s -> ~42s). 4 subprocesses chopped another ~20% of the time off (~42s > ~35s). It stopped getting faster at 4. However, the largest table took 24s, so even if this was completely parallelizable we wouldn't expect it to drop lower than that.

Getting rid of the indirect writes on handle reads would probably be nice eventually, but doesn't directly accomplish anything today.

I applied this change to 20180208.maniphest.02.populate.php:

This remains desirable, but probably won't happen without a stronger motivator since the patches are somewhat involved.

Nothing really actionable here.

• your business faces regulatory/compliance issues which are satisfied by encrypting the connection, even if it provides no direct security benefit.

I don't run my Phabricator instance on Ubuntu but instead on RHEL6 (and with PHP7, which I know isn't officially support)

(I'll follow up in T13102 if there's more to be done here, it's possible that some installs are missing this for reasons other than "Ubuntu + apt get install php5-mysql").

We generally stopped seeing this after moving to InnoDB FULLTEXT, which seems less prone to table crashes than MyISAM FULLTEXT was. See also T12819 for the fate of InnoDB FULLTEXT.

Whoops this is probably my bad :-/

Closing this for lack of feedback, feel free to resurrect it if you get back to it.