Deleting objects in two-directional "array relationship" cause reference errors - and a question...

[pkreipke]

I am using Hasura + Postgres to host my data models. In those models I have "sources" each of which can be connected from many "sinks". E.g. source_id is a FK in sinks table to an entry in sources. Hasura then represents this as an "array relationship" to a field in sources called assignedSinks.

In memory:

sources: [
{ id: 1, assignedSinks: [ { id: 11, name...} ] },
{ id: 2, assignedSinks: [ { id: 12, name...} ] }
]

sinks: [
   { id: 11, source_id: 1, label...},
   { id: 12, source_id: 2, label...}
]

I've scaffolded my models through mst-gql and loaded the code into my React Native app successfully, am able to query the data using the gen'd queries and that all is mostly fine. I have two concerns:

1. if I try to clear the data in the client using the generated stores' .clear() functions I get an error telling me that each of the sinks was already deleted earlier.

clearAll() {
  self.sources.clear()
  self.sinks.clear()
}

Error: [mobx-state-tree] You are trying to read or write to an object that is no longer part of a state tree. (Object type: 'Sources, Path upon death: '/sources/11669502-f315-4938-a95e-14ed769a7718', Subpath: 'assignedSinks'

In plain old mobx-state-tree safeReference can protect and cascade deletes so that this doesn't happen but it looks like mst-gql isn't use safeReferences.

2a) FYI I'm clearing the models first because of something related: if I run a mutation against the data that nulls out the FK value between the tables (e.g. set sinks.source_id = null, and return only sinks row, then the corresponding source's assignedUpdates is not updated at once. I think it's because Hasura delays nested updates to related tables. That's a bit too bad, don't know how to solve.

2b) But while testing that problem, I deleted a few sinks from my test data and noticed that when I refreshed my app with data from the server mst-gql's merge() functionality didn't seem to remove sinks that no longer existed on the server. I have no idea why. Perhaps the local cache? Perhaps merge can't detect deletes (how could it)? Ergo I started trying to clear out data first - see 1).

Am I doing some of these things wrong in mst-gql?

I'd be curious for any insights, thanks!

[pkreipke]

ed. renamed from 'targets' to 'sinks'.

[Benz19]

HI @pkreipke Im trying to help @jesse-savary clean up all outstanding issues... I understand this message was send back in July - Do you still have the same questions?