Support pulling Units, and other metadata from PostgreSQL datasource

[markfarnan]

What would you like to be added:

Allow PostgreSQL / Timescale plugin to pull panel metadata from the data-source. Specifically units and metric display name at a minimum, though other parameters may be useful to some panels.

Why is this needed:

A major feature of Timeseries datastores based on relational database (like Timescale) is they contain both the series, and all metadata relevant to that series. In complex IIOT use cases there can be hundreds of different units and quantity kinds in play.

For efficient dashboard creation, it is better to be able to pull this metadata (or 'overrides') from the data-source, than it is to require users to have to manually set it within the panels.

A manual approach is:

• Time consuming for operations and end users
• Error prone
• Duplicates information
• Limits highly dynamic dashboarding.

Based on chat in Slack, believe this feature requires upgrading the PostgreSQL plugin to support Data frames, which can carry this metadata, and relevant UI changes to allow for its selection.

Refer: #22918

[hugohaggmark]

@markfarnan I guess there will not be any work on this until #22918 has finished Postgres work

[markfarnan]

Looks like #22918 was completed, so any chance this functionality could now be looked at ?

I'm back looking at Grafana for a serious IoT project. Being able to pull metadata from the DB is required.

[mdvictor]

Hey @markfarnan, I understand the need for this. We need to further discuss it internally and plan for it accordingly. I cannot give you an estimate yet but I can tell you that we have this under our radar.

[gabor]

hi @markfarnan , to avoid potential misunderstandings, could you give a specific example of this behavior that you'd like to have?

for example, describe a timescaledb schema, and how it should be visible in grafana.

thanks!