What is a Dremio reflection?

A reflection is an optimized materialization of source data or a query, similar to a materialized view, that is derived from an existing table or view. A table or view that a reflection is derived from is that refection’s anchor. Dremio’s query optimizer can accelerate a query against tables or views by using one or more reflections to partially or entirely satisfy that query, rather than processing the raw data in the underlying data source. Queries do not need to reference reflections directly. Instead, Dremio rewrites queries on the fly to use the reflections that satisfy them. You can read more here: https://docs.dremio.com/cloud/reflections/