Description

absent(v) returns a 1‑element instant vector with value 1 if v matches no series; otherwise it returns an empty vector, which behaves as “falsey/non-existent” in PromQL set algebra.

absent_over_time(v[5m]) returns a 1‑element instant vector with 1 if there were no raw samples in the lookback window; otherwise it returns an empty vector, enabling time-windowed absence checks.

present_over_time(v): the value 1 for any series in the specified interval.

See for extra reference https://prometheus.io/docs/prometheus/latest/querying/functions/#absent.