Bartlomiej Plotka

This is to help with interface switch we are doing https://github.com/prometheus/prometheus/issues/17632 See https://cloud-native.slack.com/archives/C01AUBA4PFE/p1765277201832839?thread_ts=1765199584.855979&cid=C01AUBA4PFE #### Does this PR introduce a user-facing change? ```release-notes NONE ```

storage: Switch to unified, transactional AppenderV2 API; remove Appender.

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### Proposal Mentioned in various discussions ([OTLP CombinedAppender](https://github.com/prometheus/prometheus/pull/16951/files#r2256396176), [early PR](https://github.com/prometheus/prometheus/pull/17104), [PROM-60](https://github.com/prometheus/proposals/pull/60), [Slack](https://cloud-native.slack.com/archives/C01AUBA4PFE/p1764149599582409)), but this deserves a dedicated issue. We propose a replacement to our existing [`storage.Appender`](https://github.com/prometheus/prometheus/blob/b0649e08c4391c68009266779154adc72085d8cc/storage/interface.go#L262) in a form of...

Implements M1 from https://github.com/prometheus/prometheus/issues/17632 I am slowly splitting this into smaller PRs, updating https://github.com/prometheus/prometheus/issues/17632 on the way. This PR is chained on: * https://github.com/prometheus/prometheus/pull/17629 * TBD Otherwise in this PR:...

Native Summaries

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### Proposal This requires a bigger proposal, MVP and motivation, but I wanted to officially start early discussions and potential work here. The idea is to introduce the native summaries...

As discussed in https://cloud-native.slack.com/archives/C01AUBA4PFE/p1764678392087529 #### Does this PR introduce a user-facing change? ```release-notes NONE ```

[nhcb] Add PromQL compatibility layer for querying nhcb as classic histogram

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Essentially implementing logic similar to [PROM-31 reading via PromQL option 3](https://github.com/prometheus/proposals/blob/main/proposals/0031-classic-histograms-stored-as-native-histograms.md#reading-via-promql-2) but as a standalone Prometheus PromQL feature flag. ## Motivation NHCB was created to allow custom bucket use cases...

[meta] PROM-35 Remote Write (PRW2.0) Stability

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## Context This is an umbrella issue collecting things we plan to implement for **the stable [Prometheus Remote Write 2.0 (PRW2.0)](https://prometheus.io/docs/specs/prw/remote_write_spec_2_0/) protocol and Prometheus implementation**; also described by the [PROM-35](https://github.com/prometheus/proposals/pull/35)...

WAL Replay not using more memory than before the restart

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This is to track some ideas from https://github.com/prometheus/prometheus/issues/6934 The current algorithm tries to replay WAL as fast as possible after restart, which can use more memory than the Prometheus use....

promql: What if... PromQL syntax was piped (and had variables)?

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### What if... PromQL syntax was [piped](https://research.google/pubs/sql-has-problems-we-can-fix-them-pipe-syntax-in-sql/)? **DISCLAIMER ⚠️: This is for demo purposes only. Many TODOs for this code. This is just a fun discussion starter on what can...

metadata: Move caching from scrapeCache.metadata to head.series

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### Proposal As discussed on https://cloud-native.slack.com/archives/C06B8KJUU2Y/p1763451934229489 and https://github.com/prometheus/prometheus/pull/17436 we would love to have an experiment where we only cache metadata in memory once in memSeries in head, instead of the...