Oh rough, when moving an item list entry from one list to another, our
logic to merge their quantities if it's already in that list was just
fully crashing!
That is, moves without anything to merge were working, but moves that
required a merge were raising Internal Server Error 500, because the
`list_id` attribute wasn't present.
I'm not sure why this ever worked, I'm assuming using `list_id` in the
`where` condition would include it in the `select` implicitly in a
previous version of Rails? Or maybe Rails used to have fallback
behavior to run a second query, instead of raising
`MissingAttributeError` like it does now?
Well, in any case, this seems to fix it! Whew!
Okay, so I still don't know why rendering is just so slow (though
migrating away from item translations did help!), but I can at least
cache entire closet lists as a basic measure.
That way, the first user to see the latest version of a closet list
will still need just as much time to load it… but *only* the ones that
have changed since last time (rather than always the full page), and
then subsequent users get to reuse it too!
Should help a lot for high-traffic lists, which incidentally are likely
to be the big ones belonging to highly active traders!
One big change we needed to make was to extract the `user-owns` and
`user-wants` classes (which we use for trade matches for *the user
viewing the list right now*) out of the cached HTML, and apply them
after with Javascript instead. I always dislike moving stuff to JS, but
the wins here seem. truly very very good, all things considered!
It was a bit tricky to figure out the right API for this, since I'm
looking ahead to the possibility of splitting these across multiple
pages with more detail, like we do in DTI 2020.
What I like about this API is that the caller gets to apply, or not
apply, whatever scopes they want to the underlying hanger set (like
`includes` or `order`), without violating the usual syntax by e.g.
passing it as a parameter to a method.
Ahh I see, the way we got away with not having a `trading` scope before
was a weird metaprogramming `{owned/wanted}_trading` situation. Okay,
let's trash that in favor of our new stuff! And that helps us bulk the
queries too which is nice.
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!
Rails 5 added new validation on `belongs_to` to ensure the corresponding record exists. In the case of moving to the null list, this shouldn't trigger!
I wish we could flag that specifically `nil` is okay, but other values should be validated? But oh well, this is fine!
Ok so weird little situation, usually Arel will accept an attribute as a param to `order()`, but not when it's in a very specific situation of all of the following:
`Item.joins(:translations).includes(:translations).limit(30).order(Item::Translation.arel_table[:name])`
For some reason, it's all like "hey I can't call `to_sql` on an attribute!", but only in the scenario where all 3 of those other things are present. Weird!
Anyway, explicitly saying `.asc` fixes this. Ok!
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!
In the interest of clearing out Resque, I'm just gonna remove a lot of our more complex caching stuff, and we can do a perf pass for things like big item list pages once everything's upgraded. (I'm hopeful that the upgrades themselves improve perf; and if not, that some improved sensibilities 10 years later can find simpler approaches.)
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.
We'll need to replace the item search query stuff with direct MySQL queries, but that's not ready yet bc the app still isn't booting, so we're committing this in a known broken state for now!
