[hfmuehleisen]

Hi, one of the authors of DuckDB here.

ad 1) An index is an additional data structure that takes space and needs maintenance when the data changes. This is especially problematic for realtime data. DuckDBs main data structure and implementation is designed for efficient scanning without needing an additional index ("vectorised columnar").

ad 2) We support STDDEV_SAMP and STDDEV_POP. There is also an interface to define your own functions. We are very aware of how SQLite is doing things and even support their client API. But we also might eventually add their way of adding UDFs from Python.