What is the deference between EXTERNAL REFLECTION and calcites materialized view

Calcite’s materialized view can rewrite the query and compensate some join or rollup or predicate.
EXTERNAL REFLECTION also can do that?

@colagy When you say Calcite Materialized view, I assume you are talking about Dremio’s managed reflections right? As far as external reflection, you should see replacement plans. Are you not seeing it?

Does Dremio support Nested Rewriting the reflection?

@colagy what do you mean by nested rewriting?