[kdv]

Traditional views are just stored queries that are built on the fly, so there's no performance improvement. Materialized views are stored/cached on disk and will give you some performance improvements but you'll have deal with when/how the cache is updated and the resulting penalties.

[sk5t]

Yep, Postgres grants flexibility (you can build temporal materialized views + other constructs some other database servers refuse as nondeterministic) but with the burden of having to refresh the materialized view yourself. This was a little bit of a surprise after doing materialized views in MSSQL and Oracle, which treat 'em more like big old indexes updated in lockstep with the base tables.