Add two optimization TODOs for EnqueueForCompositionRevision

Signed-off-by: Nic Cope <nicc@rk0n.org>

internal/controller/apiextensions/definition/handlers.go

@@ -54,6 +54,7 @@ func EnqueueForCompositionRevision(of resource.CompositeKind, c client.Reader, l
 			xrs := kunstructured.UnstructuredList{}
 			xrs.SetGroupVersionKind(schema.GroupVersionKind(of))
 			xrs.SetKind(schema.GroupVersionKind(of).Kind + "List")
+			// TODO(negz): Index XRs by composition revision name?
 			if err := c.List(ctx, &xrs); err != nil {
 				// logging is most we can do here. This is a programming error if it happens.
 				log.Info("cannot list in CompositionRevision handler", "type", schema.GroupVersionKind(of).String(), "error", err)
@@ -62,6 +63,7 @@ func EnqueueForCompositionRevision(of resource.CompositeKind, c client.Reader, l
 
 			// enqueue all those that reference the Composition of this revision
 			compName := rev.Labels[v1.LabelCompositionName]
+			// TODO(negz): Check this before we get all XRs.
 			if compName == "" {
 				return
 			}