Dennis Zhuang a164c4a66d fix(promql): clamp extrapolation before snapping a counter to zero ...

Prometheus clamps `durationToStart` to half an average interval once the
first sample is past the extrapolation threshold, and only then lets the
counter zero-snap shorten it further, so the snap can never lengthen the
leading extrapolation. Running the snap first let it rescue a duration
the clamp should have cut, and `rate` and `increase` over-extrapolated
to the left. For samples 1@0s and 2@1s in a 4s window at 1s, upstream
gives 0.375 and this returned 0.5.

`extrapolation_matches_prometheus_on_seeded_windows` carries a
line-by-line port of upstream `extrapolatedRate` as an oracle and diffs
it against the UDF over seeded windows, so the order stays pinned.
`factor` also picked up upstream's guard against a zero sampled
interval, which previously divided by zero.

Two sqlness results move, both verified against the upstream algorithm.

Signed-off-by: Dennis Zhuang <killme2008@gmail.com>

2026-09-11 20:47:12 +08:00

..

distributed

perf(promql): push down last row for instant queries (#9034)

2026-09-09 12:38:52 +00:00

standalone

fix(promql): clamp extrapolation before snapping a counter to zero

2026-09-11 20:47:12 +08:00