Optimize out unnecessary joins when querying archetypes

crates/re_query/src/archetype_view.rs

@@ -322,24 +322,36 @@ impl<A: Archetype> ArchetypeView<A> {
         let component = self.components.get(&C::name());
 
         if let Some(component) = component {
-            let primary_instance_key_iter = self.iter_instance_keys();
-
-            let mut component_instance_key_iter = component.instance_keys().into_iter();
-
             let component_value_iter = {
                 re_tracing::profile_scope!("try_from_arrow_opt", C::name());
                 C::try_from_arrow_opt(component.values.as_arrow_ref())?.into_iter()
             };
 
+            // NOTE: Autogenerated instance keys are interned: if two or more rows in the store
+            // share the same keys, then they will literally point to the same memory address.
+            // Therefore we can compare those addresses, and early out if they match.
+            let primary_instance_key_buffer = self.required_comp().instance_keys.as_arrow_ref();
+            let component_instance_key_buffer = component.instance_keys.as_arrow_ref();
+            if primary_instance_key_buffer == component_instance_key_buffer {
+                return Ok(itertools::Either::Left(itertools::Either::Left(
+                    component_value_iter,
+                )));
+            }
+
+            let primary_instance_key_iter = self.iter_instance_keys();
+            let mut component_instance_key_iter = component.instance_keys().into_iter();
+
             let next_component_instance_key = component_instance_key_iter.next();
 
-            Ok(itertools::Either::Left(ComponentJoinedIterator {
-                primary_instance_key_iter,
-                component_instance_key_iter,
-                component_value_iter,
-                next_component_instance_key,
-                splatted_component_value: None,
-            }))
+            Ok(itertools::Either::Left(itertools::Either::Right(
+                ComponentJoinedIterator {
+                    primary_instance_key_iter,
+                    component_instance_key_iter,
+                    component_value_iter,
+                    next_component_instance_key,
+                    splatted_component_value: None,
+                },
+            )))
         } else {
             let primary = self.required_comp();
             let nulls = (0..primary.len()).map(|_| None);