Data models with StructuredValues cannot be read from Crate DB

[ilarimikkonen]

There are some data models out there where there are StructuredValues. This works fine with Orion context Broker, but when the values go with notification to QL/Crate, those values cannot be read (or at least we have not come up with a way) from Crate DB

What is the recommendation how to deal with StructuredValues in FIWARE data models.

Here is one example:

https://github.com/smart-data-models/dataModel.UrbanMobility/blob/a6b3bc03a459a106138489faab1b91ee6942cb9e/PublicTransportStop/README.md

[c0c0n3]

When a notification contains an entity with an attribute of StructuredValue type, QL saves that attribute's value in the in the corresponding CrateDB entity table with a type of object. This bit should work fine, if you come across an instance where it does not, please file a bug with QL ;-)

You should be able to retrieve the attribute as StructuredValue too, e.g. querying refPublicTransportRoute in the above example through the QL API should return a list of arrays:

...
values: [
    [ "urn:ngsi-ld:PublicTransportRoute:santander:transport:busLine:N3",
      "urn:ngsild:PublicTransportRoute:santander:transport:busLine:N4"],
    ["some:other:id", "and:yet:another"]
]
...

Again, if this doesn't work for you, we're to blame, please open an issue for it ;-)

But you can't query StructuredValue values through the QL API. We don't support that at the moment. So for example if you wanted to know how urn:ngsi-ld:PublicTransportRoute:santander:transport:busLine:N3 varied over time, you'd have to

1. query CrateDB directly; or
2. filter the result set returned by QL in your client.

Keep in mind that depending on how much data you're pulling from the DB, option 2 may be awfully inefficient. As usual there's more than one way to skin a cat, but (1) and (2) are probably what most people do? For the rest I'm not aware of any "official" recommendations, but I could be wrong :-)

[chicco785]

There was no follow-up, so we close this issue.