Query for "/meta"

[mrsimpson]

Motivation

We want to use the /meta resource to add non-mds-standard-information to entities, majorly geographies and policies.
E. g. we want to "tag" policies with a type, meaning the policy regulates a fleet.
However, we cannot query for this information easily, but we need to retrieve the full data set and filter afterwards.

Proposal

Add a query parameter to the APIs for reading entities (mds-policy, mds-geography-api) which joins and filters based on metadata. Since meta holds a JSON, this will have to translate to a fancy query on the particular services.
Imho, it's fine to query only for equality (no pattern-patching or other operators).

/policies?meta.type=fleet should be sufficient. Of course, supporting the additional jsonb operators is an option as well, but I don't know if this is consumer friendly ;)

[mrsimpson]

@avatarneil as discussed today: here's the issue. I have not found queries for meta anywhere at a first glance

[avatarneil]

Thanks for raising this issue! I think that the trickiest thing to figure out will be how to convey the JSON query in the URL, as well as what we should query the DB with. I think the solution you mentioned could work, but part of me wants to be able to just supply a JSON blob and do a partial match (similar to the Jest .toMatchObject method the whole way through...

[mrsimpson]

I thought so too, but partial matching an object is not really what queries are about (in general). I'd expect a JSON-object in the query parameter to describe the query, not the target partial object.
When it comes to formulating a query in json, I am actually quite happy with MongoDBs query document syntax. Funny enough, I just found a zero dependencies npm library which converts mongo queries to PostgreSQLs jsonb.
Looks like I am at least not the only fan of that idea ;-)