Comment by dnautics

yeah some frameworks call these "lenses". There's even crazy people who write lenses on top of elixir schemas because they dont realize you can just have multiple schemas.

maybe more concretely: if you have a table with a kajillion columns and you want performant views onto some column (e.g. "give me the metadata only and dont show me blobs columns") without pulling down the entire jungle in the sql request, There's that.