Instead of retrieving the entire list of items/characters/scores/etc. at once (and even store them in memory), use SQL's `LIMIT ... OFFSET ...` pagination so we only take what we need.
Currently only CHUNITHM uses this, but this will also affect maimai DX and O.N.G.E.K.I. once the PR is ready.
Also snuck in a fix for CHUNITHM/maimai DX's `GetUserRivalMusicApi` to respect the `userRivalMusicLevelList` sent by the client.
### How this works
Say we have a `GetUserCharacterApi` request:
```json
{
"userId": 10000,
"maxCount": 700,
"nextIndex": 0
}
```
Instead of getting the entire character list from the database (which can be very large if the user force unlocked everything), add limit/offset to the query:
```python
select(character)
.where(character.c.user == user_id)
.order_by(character.c.id.asc())
.limit(max_count + 1)
.offset(next_index)
```
The query takes `maxCount + 1` items from the database to determine if there is more items than can be returned:
```python
rows = ...
if len(rows) > max_count:
# return only max_count rows
next_index += max_count
else:
# return everything left
next_index = -1
```
This has the benefit of not needing to load everything into memory (and also having to store server state, as seen in the [`SCORE_BUFFER` list](2274b42358/titles/chuni/base.py (L13)).)
Reviewed-on: https://gitea.tendokyu.moe/Hay1tsme/artemis/pulls/185
Co-authored-by: beerpsi <beerpsi@duck.com>
Co-committed-by: beerpsi <beerpsi@duck.com>
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