Fix code talking about "views" instead of subscribers (#4591)

_Starting to cherry-pick some of the stuff buried in my caching branch_

Trivial.

crates/re_arrow_store/src/store_event.rs

@@ -498,7 +498,7 @@ mod tests {
             assert!(event.cells.contains_key(&store.cluster_key()));
 
             let (events, _) = store.gc(&GarbageCollectionOptions::gc_everything());
-            assert!(events.len() == 1);
+            assert_eq!(1, events.len());
             assert!(events[0].cells.contains_key(&store.cluster_key()));
         }
 
@@ -515,7 +515,7 @@ mod tests {
             assert!(!event.cells.contains_key(&store.cluster_key()));
 
             let (events, _) = store.gc(&GarbageCollectionOptions::gc_everything());
-            assert!(events.len() == 1);
+            assert_eq!(1, events.len());
             assert!(!events[0].cells.contains_key(&store.cluster_key()));
         }
 

crates/re_arrow_store/src/store_subscriber.rs

@@ -13,7 +13,7 @@ type SharedStoreSubscriber = RwLock<Box<dyn StoreSubscriber>>;
 //
 // TODO(#4204): StoreSubscriber should require SizeBytes so they can be part of memstats.
 pub trait StoreSubscriber: std::any::Any + Send + Sync {
-    /// Arbitrary name for the view.
+    /// Arbitrary name for the subscriber.
     ///
     /// Does not need to be unique.
     fn name(&self) -> String;
@@ -36,7 +36,7 @@ pub trait StoreSubscriber: std::any::Any + Send + Sync {
 
     /// The core of this trait: get notified of changes happening in all [`DataStore`]s.
     ///
-    /// This will be called automatically by the [`DataStore`] itself if the view has been
+    /// This will be called automatically by the [`DataStore`] itself if the subscriber has been
     /// registered: [`DataStore::register_subscriber`].
     /// Or you might want to feed it [`StoreEvent`]s manually, depending on your use case.
     ///
@@ -72,65 +72,67 @@ impl DataStore {
     /// ## Scope
     ///
     /// Registered [`StoreSubscriber`]s are global scope: they get notified of all events from all
-    /// existing [`DataStore`]s, including [`DataStore`]s created after the view was registered.
+    /// existing [`DataStore`]s, including [`DataStore`]s created after the subscriber was registered.
     ///
     /// Use [`StoreEvent::store_id`] to identify the source of an event.
     ///
     /// ## Late registration
     ///
-    /// Views must be registered before a store gets created to guarantee that no events were
-    /// missed.
+    /// Subscribers must be registered before a store gets created to guarantee that no events
+    /// were missed.
     ///
     /// [`StoreEvent::event_id`] can be used to identify missing events.
     ///
     /// ## Ordering
     ///
-    /// The order in which registered views are notified is undefined and will likely become
+    /// The order in which registered subscribers are notified is undefined and will likely become
     /// concurrent in the future.
     ///
-    /// If you need a specific order across multiple views, embed them into an orchestrating view.
+    /// If you need a specific order across multiple subscribers, embed them into an orchestrating
+    /// subscriber.
     //
     // TODO(cmc): send a compacted snapshot to late registerers for bootstrapping
-    pub fn register_subscriber(view: Box<dyn StoreSubscriber>) -> StoreSubscriberHandle {
-        let mut views = SUBSCRIBERS.write();
-        views.push(RwLock::new(view));
-        StoreSubscriberHandle(views.len() as u32 - 1)
+    pub fn register_subscriber(subscriber: Box<dyn StoreSubscriber>) -> StoreSubscriberHandle {
+        let mut subscribers = SUBSCRIBERS.write();
+        subscribers.push(RwLock::new(subscriber));
+        StoreSubscriberHandle(subscribers.len() as u32 - 1)
     }
 
-    /// Passes a reference to the downcasted view to the given callback.
+    /// Passes a reference to the downcasted subscriber to the given callback.
     ///
-    /// Returns `None` if the view doesn't exist or downcasting failed.
+    /// Returns `None` if the subscriber doesn't exist or downcasting failed.
     pub fn with_subscriber<V: StoreSubscriber, T, F: FnMut(&V) -> T>(
         StoreSubscriberHandle(handle): StoreSubscriberHandle,
         mut f: F,
     ) -> Option<T> {
-        let views = SUBSCRIBERS.read();
-        views.get(handle as usize).and_then(|view| {
-            let view = view.read();
-            view.as_any().downcast_ref::<V>().map(&mut f)
+        let subscribers = SUBSCRIBERS.read();
+        subscribers.get(handle as usize).and_then(|subscriber| {
+            let subscriber = subscriber.read();
+            subscriber.as_any().downcast_ref::<V>().map(&mut f)
         })
     }
 
-    /// Passes a mutable reference to the downcasted view to the given callback.
+    /// Passes a mutable reference to the downcasted subscriber to the given callback.
     ///
-    /// Returns `None` if the view doesn't exist or downcasting failed.
+    /// Returns `None` if the subscriber doesn't exist or downcasting failed.
     pub fn with_subscriber_mut<V: StoreSubscriber, T, F: FnMut(&mut V) -> T>(
         StoreSubscriberHandle(handle): StoreSubscriberHandle,
         mut f: F,
     ) -> Option<T> {
-        let views = SUBSCRIBERS.read();
-        views.get(handle as usize).and_then(|view| {
-            let mut view = view.write();
-            view.as_any_mut().downcast_mut::<V>().map(&mut f)
+        let subscribers = SUBSCRIBERS.read();
+        subscribers.get(handle as usize).and_then(|subscriber| {
+            let mut subscriber = subscriber.write();
+            subscriber.as_any_mut().downcast_mut::<V>().map(&mut f)
         })
     }
 
-    /// Called by [`DataStore`]'s mutating methods to notify view subscribers of upcoming events.
+    /// Called by [`DataStore`]'s mutating methods to notify subscriber subscribers of upcoming events.
     pub(crate) fn on_events(events: &[StoreEvent]) {
-        let views = SUBSCRIBERS.read();
+        re_tracing::profile_function!();
+        let subscribers = SUBSCRIBERS.read();
         // TODO(cmc): might want to parallelize at some point.
-        for view in views.iter() {
-            view.write().on_events(events);
+        for subscriber in subscribers.iter() {
+            subscriber.write().on_events(events);
         }
     }
 }