In impress-2020, we do a big slow query to figure out which users have
been active in trades recently. Now, we cache that timestamp on the
User model.
This won't have any immediate effect; it's to clear the way for Classic
DTI to receive the better trade ratios feature people like from 2020.
I also added some unit testing infra because I finally wanted it! for
all the ways you can trigger this timestamp lol
Note too that this is a bit of an unusually complex migration, but my
hope is that the batching and query structure and such helps it run
surprisingly fast! 🤞
I used the new profiler tools on this page, and noticed a lot of
allocations in the Globalize library, which we use for translating
database records. I realized that we were loading all of the fields of
not just all of the items on the page, but all of their translation
records in all locales! We used to scrape data for lots of languages, so
that can be quite a lot!
Unfortunately, Rails's `includes` method to efficiently preload related
records always loads all fields, and simply can't be overridden.
So, in this change we write manual preloading code, to identify the
records we need, load them in big bulk queries, and assign them back to
the appropriate associations. Basically just what `includes` does, but
written out a bit more, to give us the chance to specify SELECT and
WHERE clauses!
Idk if this used to be different or what, but it looks like the current
behavior is: if you delete a closet list, it'll leave the hangers
present, but Classic DTI would not show them anywhere; but Impress 2020
(until recently) would crash about it.
Now, we use `dependent: :destroy` to delete the hangers when you delete
the list (which I think makes sense, and is different than what I
decided in the past but that's ok, and is what the current behavior
*looks* like to people!), and we add a migration that deletes orphaned
hangers.
The migration also outputs the deleted hangers as JSON, for us to hold
onto in case we made a mistake! I'm also backing up the database in
advance of running this migration, just in case we gotta roll back HARD!
Some important little upgrades but mostly straightforward!
Note that there's still a known issue where item searches crash, I was hoping that this was a bug in Rails 4.2 that would be fixed on upgading to 5, but nope, oh well!
Also uhh I just got a bit silly and didn't actually mean to go all the way to 5.2 in one go, I had meant to start at 5.0… but tbh the 5.1 and 5.2 changes seem small, and this seems to be working, so. Yeah ok let's roll!
Idk this one might actually be a bit of a pain to load? But I'd want to optimize it differently anyway, and there's overhauls we're already planning to do here.
Ohh ok, without this change all of our `scope`s were just immediately evaluating the argument and fetching _all_ such matching records immediately, instead of waiting to actually be called. This led to bugs like `pet_type.as_json` returning ALL pet states in the whole db, because the `PetState.emotion_order` scope was being treated as a single predefined query, rather than a query fragment to merge into the current context.
This also explains what happened in 724ed83: that's why things before the scope in the query were being ignored.
