:wave: What could be the reason for `selectAsFlow` to return an empty array when 100% there’s data i...

# supabase-kt

[Nacho Ruiz Martin]

👋
What could be the reason for selectAsFlow to return an empty array when 100% there’s data in the table that matches the filter?

[Jan]

Could be misconfigured RLS policies/a signed out user. Does the "normal" select work?

[Nacho Ruiz Martin]

Oh, the normal select is also empty 🤔

[Nacho Ruiz Martin]

I’ll check RLS policies now

[Nacho Ruiz Martin]

That looks correct:

[Nacho Ruiz Martin]

Ok, it was RLS, thanks, man 🙂

[Nacho Ruiz Martin]

Sorry to disturb again, in the same operation now I’m getting an infinite loop of Supabase connecting to the realtime websocket. What could be the reason for that?

[Jan]

Can you share the whole log?

[Nacho Ruiz Martin]

This is everything (Kotlin/JS)

[Jan]

Thanks, and the message "Connected to realtime websocket!" indicates the problem? It shouldn't be possible that this message gets sent more than once without any other realtime log

[Nacho Ruiz Martin]

Yeah, it’s getting sent again and again (the 193 on the left indicates the ammount).

[Jan]

Not sure what could cause this, just tried a small snippet on K/JS and it works as expected:

fun main() {
    GlobalScope.launch {
        val supabase = createSupabaseClient(
            supabaseUrl = "",
            supabaseKey = ""
        ) {
            install(Auth)
            install(Realtime)
            install(Postgrest)
        }
        val flow = supabase.from("messages").selectAsFlow(Message::id)
        flow.collect {
            println(it)
        }
    }
}

Can you share your code?

[Nacho Ruiz Martin]

🤔 Yes, but it’s quite complex.

[Nacho Ruiz Martin]

This is the flow:

@OptIn(SupabaseExperimental::class)
    private suspend fun getPubsByManagerStream(userId: String): Flow<List<Pub>> =
        supabase.from("pub_admin")
            .selectAsFlow(
                primaryKeys = listOf(PubAdmin::pub, PubAdmin::user),
                filter = FilterOperation("user", FilterOperator.EQ, userId)
            )
            .flatMapLatest { adminPubs ->
                if (adminPubs.isEmpty()) flowOf(emptyList())
                else combine(adminPubs.map { (pubId, _) -> pubsService.getPubDetailsStream(pubId) }) {
                    it.toList()
                }
            }

[Jan]

is getPubDetailsStream also using realtime?

[Nacho Ruiz Martin]

Yes:

@OptIn(SupabaseExperimental::class)
    override suspend fun getPubDetailsStream(pubId: Int): Flow<Pub> =
        supabase.from(tableName)
            .selectSingleValueAsFlow(Pub::id) {
                Pub::id eq pubId
            }

[Nacho Ruiz Martin]

I suspect of some misconfiguration in the DB, though, because I’ve seen this code working.

[Nacho Ruiz Martin]

If you don’t know what could cause it from the top of your head, don’t worry, I’ll investigate the whole DB thing on my side.

[Jan]

.flatMapLatest { adminPubs ->
                if (adminPubs.isEmpty()) flowOf(emptyList())
                else combine(adminPubs.map { (pubId, _) -> pubsService.getPubDetailsStream(pubId) }) {
                    it.toList()
                }
            }

So for every change you are basically retrieving details & listening for changes on them each on their own?

[Nacho Ruiz Martin]

Yes

[Nacho Ruiz Martin]

The list will get updated in number and content

[Jan]

I'm wondering if that could cause the creation of an basically infinite growing amount of flows and therefore realtime channels as you repeatedly call selectSingleValueAsFlow for every pub on every change. Not sure if these unused flows get cancelled at all 🤔

[Jan]

> Not sure if these unused flows get cancelled at all
As a result, the realtime channels are never left. That would probably be hard to debug, but you can try to print out Realtime#subscriptions to check how many channels are used. That would be one for getPubsByManagerStream and one each for getPubDetailsStream calls

[Nacho Ruiz Martin]

Thanks! I'll take a deeper look into that.

[Nacho Ruiz Martin]

A single `selectAsFlow`with all the items would be the same result.

[Nacho Ruiz Martin]

This infinite loop was caused due to a serialisation error in one of the objects. For some reason, in the case of an error, the whole flow was retried infinitely. sad panda