Introduce Loki connector.

[jeschkies]

Description

This change introduce a Loki connector. It supports log and metric queries.

Additional context and related issues

Currently the connector uses the older ResultSetProvider. A PageSourceProvider is planned as is predicate push down.

This is a side project. There is no official support from Grafana Labs.

Release notes

( ) This is not user-visible or is docs only, and no release notes are required. (x) Release notes are required. Please propose a release note for me. ( ) Release notes are required, with the following suggested text:

Co-authored-by: Janos [email protected]

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[jeschkies]

We are going to add tests before the merge.

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[jeschkies]

@Praveen2112 thanks for this thorough review. There was some great feedback. I've reacted with :+1: to everything I've addressed.

The last open question is on the timestamp as a function parameter https://github.com/trinodb/trino/pull/23053#discussion_r1758816366. I'd need some help with that.

[jeschkies]

How is timestamp is represented in Loki ?

It depends where. Most of the time it's the Prometheus' model.Time which wraps a 64bit int as milliseconds since epoch. Sometimes it's a 64bit int for nanoseconds since epoch and other times it's Go's Time which has a nanoseconds resolution.

As for the API it's one of four timestamps formats.

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This pull request has gone a while without any activity. Tagging for triage help: @mosabua

[mosabua]

Would @jeschkies and @Praveen2112 be interested to join me as guest for Trino Community Broadcast to talk about the connector and Loki and demo it a bit?

[Praveen2112]

@jeschkies Thanks a lot for working on this. Can we also have a docs for this connector ?