New data APIs 2: cached latest-at queries

[teh-cmc]

Static-aware, key-less, component-based, cached latest-at APIs.

The overall structure of this new cache is very similar to what we had before. Effectively it is just an extremely simplified version of re_query_cache.

This introduces a new temporary re_query_cache2 crate, which won't ever be published.
It will replace the existing re_query_cache crate once all the necessary features have been backported.

• Fixes Track RowId for secondary components  #3232
• Fixes Primary cache: don't denormalize auto-generated instance keys #4733
• Fixes Primary cache: don't denormalize splatted values #4734
• Part of Expose ArchetypeView API to deal with raw arrow buffers when join is bypassed #3379
• Part of Eliminate legacy splats #1893

Example:

let caches = re_query_cache2::Caches::new(&store);

// First, get the results for this query.
//
// They might or might not already be cached. We won't know for sure until we try to access
// each individual component's data below.
let results: CachedLatestAtResults = caches.latest_at(
    &store,
    &query,
    &entity_path.into(),
    MyPoints::all_components().iter().cloned(), // no generics!
);

// Then, grab the results for each individual components.
// * `get_required` returns an error if the component batch is missing
// * `get_optional` returns an empty set of results if the component if missing
// * `get` returns an option
//
// At this point we still don't know whether they are cached or not. That's the next step.
let points: &CachedLatestAtComponentResults = results.get_required::<MyPoint>()?;
let colors: &CachedLatestAtComponentResults = results.get_optional::<MyColor>();
let labels: &CachedLatestAtComponentResults = results.get_optional::<MyLabel>();

// Then comes the time to resolve/convert and deserialize the data.
// These steps have to be done together for efficiency reasons.
//
// Both the resolution and deserialization steps might fail, which is why this returns a `Result<Result<T>>`.
// Use `PromiseResult::flatten` to simplify it down to a single result.
//
// A choice now has to be made regarding the nullability of the _component batch's instances_.
// Our IDL doesn't support nullable instances at the moment -- so for the foreseeable future you probably
// shouldn't be using anything but `iter_dense`.
//
// This is the step at which caching comes into play.
//
// If the data has already been accessed with the same nullability characteristics in the
// past, then this will just grab the pre-deserialized, pre-resolved/pre-converted result from
// the cache.
//
// Otherwise, this will trigger a deserialization and cache the result for next time.

let points = match points.iter_dense::<MyPoint>(&mut resolver).flatten() {
    PromiseResult::Pending => {
        // Handle the fact that the data isn't ready appropriately.
        return Ok(());
    }
    PromiseResult::Ready(data) => data,
    PromiseResult::Error(err) => return Err(err.into()),
};

let colors = match colors.iter_dense::<MyColor>(&mut resolver).flatten() {
    PromiseResult::Pending => {
        // Handle the fact that the data isn't ready appropriately.
        return Ok(());
    }
    PromiseResult::Ready(data) => data,
    PromiseResult::Error(err) => return Err(err.into()),
};

let labels = match labels.iter_sparse::<MyLabel>(&mut resolver).flatten() {
    PromiseResult::Pending => {
        // Handle the fact that the data isn't ready appropriately.
        return Ok(());
    }
    PromiseResult::Ready(data) => data,
    PromiseResult::Error(err) => return Err(err.into()),
};

// With the data now fully resolved/converted and deserialized, the joining logic can be
// applied.
//
// In most cases this will be either a clamped zip, or no joining at all.

let color_default_fn = || {
    static DEFAULT: MyColor = MyColor(0xFF00FFFF);
    &DEFAULT
};
let label_default_fn = || None;

let results =
    clamped_zip_1x2(points, colors, color_default_fn, labels, label_default_fn).collect_vec();

---

Part of a PR series to completely revamp the data APIs in preparation for the removal of instance keys and the introduction of promises:

• New data APIs 0: ClampedZip iterator machinery #5573
• New data APIs 1: uncached latest-at queries #5574
• New data APIs 2: cached latest-at queries #5581
• New data APIs 3: Send/Sync/'static Component, once and for all #5605
• New data APIs 4: cached latest-at mono helpers everywhere #5606
• New data APIs 5: port data UIs to new APIs #5633
• New data APIs 6: cached archetype queries #5673
• New data APIs 7: RangeZip iterator machinery #5679
• New data APIs 8: uncached range queries #5687
• New data APIs 9: cached range queries #5755
• TODO
• TODO

Builds on top of the static data PR series:

• Static data 0: revamped TimeInt #5534

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using newly built examples: app.rerun.io
  • Using examples from latest main build: app.rerun.io
  • Using full set of examples from nightly build: app.rerun.io
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
• If applicable, add a new check to the release checklist!

• PR Build Summary
• Docs preview
• Examples preview
• Recent benchmark results
• Wasm size tracking

[teh-cmc]

❗

[teh-cmc]

Most of these aren't used yet and were just imported as-is from re_query_cache -- they'll become use very soon as re_query_cache2 reaches feature parity.

[teh-cmc]

Imported as-is from re_query_cache

[teh-cmc]

Imported as-is from re_query_cache

[teh-cmc]

Imported as-is from re_query_cache

[teh-cmc]

Very similar to the same file in re_query_cache, just simpler.

[teh-cmc]

Imported as-is from re_query_cache

[teh-cmc]

Github won't let me link these two issues:

• Fixes Primary cache: don't denormalize auto-generated instance keys #4733
• Fixes Primary cache: don't denormalize splatted values #4734

Reminder to close them manually after...

[emilk]

It's really nice to have these simple examples ⭐