Indeed. Previously, when computing latency histograms from sampled events, I've abused DuckDB SQL cross join/cartesian products to generate zero values for "empty buckets" within a single SQL statement [1]. But makes the SQL unnecessarily complex & slower too, so I quickly moved that empty bucket rendering functionality to the frontend...
[1]: Example DuckDB SQL with generated bucket lists and cross join + outer join: https://github.com/tanelpoder/0xtools/blob/master/tools/sql/...
Feature author here. The new FILL uses linear interpolation (and extrapolation at the ends). There were a bunch of other algorithms requested (e.g., cubic splines), but the syntax was not clear.
I think the real solution is to add support for non-aggregate window functions in the catalogue. Right now, they are all hard-coded, but if they were extensible, there are a number applications in addition to filling that could be supported.