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2 Commits
Author SHA1 Message Date
dennis zhuang 78a7b93292 fix(promql): align timestamp(), label_join and label_replace with Prometheus semantics (#9385)
* fix(promql): align timestamp() and label_join with Prometheus semantics

- timestamp() over a selector reports the selected sample's timestamp, without adding the offset.
- timestamp() over any other expression reports the evaluation time instead of the input value.
- label_join that overwrites an existing label rejects duplicate label sets at runtime.

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

* fix(promql): align label_replace and label_join edge cases with Prometheus

- label_replace leaves non-matching series unchanged instead of copying the source value into the destination label.
- label_replace may overwrite an existing label; duplicate label sets are rejected at runtime like label_join.
- label_join with no source labels removes the destination label, and an empty source label name is rejected.
- Empty label values produced by these functions are NULL, the same as an absent label.

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

* fix(promql): join absent labels as empty strings in label_join

concat_ws skips NULL arguments together with their separator, so a label that is absent (NULL) dropped its separator, e.g. label_join(label_join(vector(1), "a", "", "missing"), "b", "-", "a", "a") lost b="-". Read every source label as coalesce(label, '') like label_replace does.

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

* fix(promql): skip rows without a sample in timestamp()

timestamp() replaced the input fields with the timestamp before the empty-value filter ran, so a row whose fields were all NULL got a timestamp, e.g. timestamp(-m) for a NULL sample. Filter such rows before the projection, for both the selector and the evaluation-time paths.

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

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Signed-off-by: Dennis Zhuang <killme2008@gmail.com>
2026-09-30 01:42:11 +00:00
discord9 28e415a103 feat(query): implement PromQL @ modifier on vector and matrix selectors (#9224)
* feat(query): implement PromQL @ modifier on vector and matrix selectors

The planner previously dropped the `at` field of selectors (`at: _`),
so `some_metric @ 300` silently returned step-following values instead
of the samples anchored at the fixed timestamp.

Anchoring follows Prometheus's `setOffsetForAtModifier` + `refetch`
semantics: resolve the anchor (`@ <ts>`, `@ start()`, `@ end()`), apply
`offset` to the anchor, rewrite the selector offset to
`eval_start - anchor`, scan only the anchored window, then report the
same window at every evaluation step via a grid-wide-replay
`InstantManipulate`. `@ start()` / `@ end()` resolve against the
statement's evaluation range (`stmt_start` / `stmt_end`), which subquery
planning does not rewrite.

Timestamps before the Unix epoch are accepted; unrepresentable ones are
rejected with `AtModifierTimestampOutOfRange` instead of wrapping.
Selectors without `@` are planned exactly as before.

Report: .e-agent/greptimedb_promql_compatibility_report_2026-09-16.md P0-2
Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>

* fix(promql): center predict_linear on the evaluation timestamp

predict_linear_impl used the window's last sample time as the evaluation
timestamp, and the UDF took only (ts_range, value_range, t) with no channel
for the current instant. After a range selector is folded for @ (or with an
offset) the same window is replayed at every step, so the prediction stayed
constant at the anchor's answer; even a plain window ended before the step
produced a stale value.

Give prom_predict_linear a 4th argument carrying the step's evaluation
instant (ms timestamp), derived in the planner from the row's time index
plus the offset the window was folded with (at_offset for @, offset_ms
otherwise, recorded on PromPlannerContext). The regression is centered on
that instant, matching Prometheus' use of enh.Ts. The mixed
float/native-histogram path forwards the same argument.

Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>

* refactor(query): tighten @ modifier planner and predict_linear

- range_fold_offset is always a concrete millisecond offset, not an
  Option; the single-step replay helper no longer wraps an infallible
  plan in Result.
- predict_linear's eval timestamp is always cast to Timestamp(ms) at the
  call site, so the UDF drops its dead Int64 branch and the extra
  func_name argument.
- Drop two redundant comparison cases from the at_modifier sqlness test
  and fix the lookback window comment to the half-open (0s, 300s].

Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>

* test(query): accept parse-time rejection of @ on Windows

`@ 1e16` is 10^19 milliseconds, beyond i64::MAX. A Unix SystemTime
holds it and the planner rejects the anchor it cannot represent, but a
Windows SystemTime tops out near 1.8e12 seconds, so the parser's
checked_add fails first and the same literal is rejected while parsing.
Accept either rejection path so the test passes on both platforms.

Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>

* fix(query): avoid replaying label_join over rewritten series keys

Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>

* fix(query): narrow anchored range call promotion

Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>

* fix(query): address @ modifier review feedback

Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>

* fix(query): satisfy super import format check

Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>

* docs(query): address at modifier review follow-ups

Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>

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Signed-off-by: discord9 <55937128+discord9@users.noreply.github.com>
2026-09-28 09:38:12 +00:00