Feature Request: Supabase Extension for Loon

[sennraf]

Thank you for developing Loon. Looks great. Is it possible to use it with supabase?

[danReynolds]

Hey! Yea I havent used Supabase before. It looks cool. I'll need to look into writing an adapter but it should definitely be possible. Probably not too hard.

Does it currently persist data for you? Is there something about using Loon with it that would make things easier for you or you're interested in?

Have a good one

[sennraf]

The reason why Loon would be interesting is because the supabase package currently does not persist data for you.

[danReynolds]

Oh cool yea I see now that they recommend SharedPreferences currently as the solution: https://pub.dev/packages/supabase_flutter#a-idcustom-localstorageacustom-localstorage

Yea looks like that could go to Loon instead. I'm going to play around with Supabase a bit.

[danReynolds]

So i looked through the Supabase package last night. It's cool, it definitely doesn't try to persist the Postgres data. I think it would be more challenging to write than the Firestore extension for a couple reasons:

1. It has a very private API, so you'd have to really wrap everything like all the filters in https://github.com/supabase/supabase-flutter/blob/main/packages/postgrest/lib/src/postgrest_filter_builder.dart which is somewhat tedious/error prone.

2. It's basically just a client for interacting with your Postgres database hosted by Supabase. So essentially writing a caching layer on the client would be equivalent to somewhat implementing a sizable subset of the Postgres spec and then translating it all to how Loon represents data in collections and documents. It is do-able, but pretty involved and I'd say the bigger issue is just that it doesn't seem like the right way to be handling it. The optimal solution would be writing a proper Postgres compatible SQL-style persistence client.

That said, it does support realtime streaming and table watching:
https://pub.dev/packages/supabase_flutter

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If you're comfortable streaming changes to your table then what you could do is like in the image, subscribe to all changes and then dump that into a local persistent cache like Loon.

An example might look like this:

client
  .channel('public:todos')
  .onPostgresChanges(
      event: PostgresChangeEvent.all,
      schema: 'public',
      table: 'todos',
      callback: (payload) {
        print(payload);
        // {
        //   'schema': 'public',
        //   'table': 'todos',
        //   'commit_timestamp': '2021-08-01T08:00:30Z',
        //   'eventType': 'UPDATE',
        //   'new': {'id': 2, 'task': 'task 2 updated', 'status': false},
        //   'old': {'id': 2},
        //   'errors': null
        // }
        final newData = payload['new'];
        final docId = newData['id'];
        Loon.collection('todos').doc(docId).update(newData);
      });

That gets you part of the way there by at least letting you persist your data and then access it reactively through Loon across your application. Given how simple that is, I don't think it needs a full extension right now, maybe just a doc suggesting that if you want to persist to Supabase data to Loon then this approach could be an option to consider. It relies on using the streaming capabilities in Supabase though.

Let me know what you think and if you know other Flutter devs using Supabase it'd be cool to hear if they can think of a better solution.

[rayliverified]

Have you seen the discussions about Supabase building offline sync into their own packages?

https://github.com/orgs/supabase/discussions/357

[sennraf]

thanks @danReynolds for the detailed write up. I will try the approach with streaming db changes into loon.