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dennis zhuang
99bf6a8403
I hereby agree to the terms of the [GreptimeDB CLA](https://github.com/GreptimeTeam/.github/blob/main/CLA.md). ## Refer to a related PR or issue link (optional) Narthex operator task NEW-MAP-FN, remaining part. ## What's changed and what's your intention? Adds the native kernel for the experimental `histogram_quantiles(v, label, q...)` from Prometheus v3.15.0. - `histogram_eval::histogram_quantiles` evaluates `histogram_quantile` for each `q` with the existing kernel and sets `label` to `q`, formatted as Prometheus' `labels.FormatOpenMetricsFloat` does. Results that then share a label set merge through `merge_same_labelset`. A repeated `q`, or a `label` that overwrites the label telling two histograms apart, fails at a point both hold, as in Prometheus. - The Go float formatting from #9799's `count_values` moves to a `go_format` module, next to `go_sort`. It now offers both `FormatFloat(v, 'f', -1, 64)` and `FormatOpenMetricsFloat`, which is Go's shortest `'g'` format: an exponent below 1e-4 and from 1e6 on, at least two exponent digits, `.0` appended to integers, and hardcoded `0.0`, `1.0`, `-1.0`. Both share the round-trip-checked shortest digits. ### Tests - `histogram_eval/quantiles_cases.txt` (37 KB, 30 cases): classic histograms evaluated by the Prometheus engine with experimental functions on (promql-compat `narthex-golden-histogram -quantiles`). It includes repeated quantiles and `job` as the quantile label; 13 cases end in the label set collision. - `go_format/open_metrics_cases.txt` (13 KB, 358 values): `FormatOpenMetricsFloat` outputs for the exponent switch points, the hardcoded values, powers of two from 2^-30 to 2^30 with neighbours, and random values (`narthex-golden-formatfloat -openmetrics`). The existing `'f'` fixture is unchanged. ## PR Checklist Please convert it to a draft if some of the following conditions are not met. - [x] I have written the necessary rustdoc comments. - [x] I have added the necessary unit tests and integration tests. - [ ] This PR requires documentation updates. - [x] API changes are backward compatible. - [x] Schema or data changes are backward compatible. - [ ] This PR needs to be backported to release branches, and I have added the `backport-<target>` labels (e.g. `backport-v1.3` targets `release/v1.3`).