Primary caching 15: range read performance optimization (#4800)

The most obvious and most important performance optimization when doing
cached range queries: only upsert data at the edges of the bucket /
ring-buffer.

This works because our buckets (well, singular, at the moment) are
always dense.

- #4793  

![image](https://github.com/rerun-io/rerun/assets/2910679/7246827c-4977-4b3f-9ef9-f8e96b8a9bea)
- #4800:

![image](https://github.com/rerun-io/rerun/assets/2910679/ab78643b-a98b-4568-b510-2b8827467095)

---

Part of the primary caching series of PR (index search, joins,
deserialization):
- #4592
- #4593
- #4659
- #4680 
- #4681
- #4698
- #4711
- #4712
- #4721 
- #4726 
- #4773
- #4784
- #4785
- #4793
- #4800

Author: teh-cmc

crates/re_query_cache/src/range.rs

@@ -19,6 +19,65 @@ pub struct RangeCache {
     pub total_size_bytes: u64,
 }
 
+impl RangeCache {
+    /// Given a `query`, returns N reduced queries that are sufficient to fill the missing data
+    /// on both the front & back sides of the cache.
+    #[inline]
+    pub fn compute_queries(&self, query: &RangeQuery) -> impl Iterator<Item = RangeQuery> {
+        let front = self.compute_front_query(query);
+        let back = self.compute_back_query(query);
+        front.into_iter().chain(back)
+    }
+
+    /// Given a `query`, returns a reduced query that is sufficient to fill the missing data
+    /// on the front side of the cache, or `None` if all the necessary data is already
+    /// cached.
+    pub fn compute_front_query(&self, query: &RangeQuery) -> Option<RangeQuery> {
+        let mut reduced_query = query.clone();
+
+        if self.bucket.is_empty() {
+            return Some(reduced_query);
+        }
+
+        if let Some(bucket_time_range) = self.bucket.time_range() {
+            reduced_query.range.max = TimeInt::min(
+                reduced_query.range.max,
+                bucket_time_range.min.as_i64().saturating_sub(1).into(),
+            );
+        } else {
+            return Some(reduced_query);
+        }
+
+        if reduced_query.range.max < reduced_query.range.min {
+            return None;
+        }
+
+        Some(reduced_query)
+    }
+
+    /// Given a `query`, returns a reduced query that is sufficient to fill the missing data
+    /// on the back side of the cache, or `None` if all the necessary data is already
+    /// cached.
+    pub fn compute_back_query(&self, query: &RangeQuery) -> Option<RangeQuery> {
+        let mut reduced_query = query.clone();
+
+        if let Some(bucket_time_range) = self.bucket.time_range() {
+            reduced_query.range.min = TimeInt::max(
+                reduced_query.range.min,
+                bucket_time_range.max.as_i64().saturating_add(1).into(),
+            );
+        } else {
+            return Some(reduced_query);
+        }
+
+        if reduced_query.range.max < reduced_query.range.min {
+            return None;
+        }
+
+        Some(reduced_query)
+    }
+}
+
 // --- Queries ---
 
 macro_rules! impl_query_archetype_range {
@@ -80,7 +139,7 @@ macro_rules! impl_query_archetype_range {
                 $($pov: Component + Send + Sync + 'static,)+
                 $($comp: Component + Send + Sync + 'static,)*
             {
-                re_log::trace!("fill");
+                re_tracing::profile_scope!("fill");
 
                 let now = web_time::Instant::now();
 
@@ -112,14 +171,16 @@ macro_rules! impl_query_archetype_range {
             let mut range_callback = |query: &RangeQuery, range_cache: &mut crate::RangeCache| {
                 re_tracing::profile_scope!("range", format!("{query:?}"));
 
-                let RangeCache { bucket, total_size_bytes } = range_cache;
-
-                // NOTE: `+ 2` because we always grab the indicator component as well as the
-                // instance keys.
-                let arch_views = ::re_query::range_archetype::<A, { $N + $M + 2 }>(store, query, entity_path);
-                *total_size_bytes += upsert_results::<A, $($pov,)+ $($comp,)*>(arch_views, bucket)?;
+                for reduced_query in range_cache.compute_queries(query) {
+                    // NOTE: `+ 2` because we always grab the indicator component as well as the
+                    // instance keys.
+                    let arch_views =
+                        ::re_query::range_archetype::<A, { $N + $M + 2 }>(store, &reduced_query, entity_path);
+                    range_cache.total_size_bytes +=
+                        upsert_results::<A, $($pov,)+ $($comp,)*>(arch_views, &mut range_cache.bucket)?;
+                }
 
-                iter_results(bucket)
+                iter_results(&range_cache.bucket)
             };