Hey! Currently in MPP we are using SqlDelight and...

# multiplatform

[aiidziis]

Hey! Currently in MPP we are using SqlDelight and coroutines to insert data into db:

class DbHelper(db: Db) {
    suspend fun insert(elements: List<Element>) = withContext(Dispatchers.Default) {
        db.elementQueries.transaction {
            db.elementQueries.insert(.....)
        }
    }
}

This works fine when elements list is not too big, but now we encountered use case where we need to insert larger amount of data (in worst case insert is 1200ms), and now this same approach is causing problems on iOS because this all happens on Main Thread(async) , and while the data is inserting UI is getting blocked when user interacts with UI (scrolling).

Is there a way with current coroutines versions "1.3.5-native-mt" to improve this? afaik with current coroutines version it is not possible move insert to Background Thread?

[louiscad]

@aiidziis Yes, native-mt makes Dispatchers.Default be on a background thread.

[aiidziis]

Hm, then I guess UI is getting blocked by something else?
I have scope defined like this:

internal class EngineScope : CoroutineScope {
    internal val job = SupervisorJob()

    override val coroutineContext: CoroutineContext
        get() = Dispatchers.Main + job
}

and I am calling this insert function:

engineScope.launch { dbHelper.insert(elements) }

So this shouldn’t block main thread?

[louiscad]

@aiidziis You can log the result of NSThread.isMainThread at the right place to find out.
(Needs import of import platform.Foundation.NSThread) You might need to expect/actual it if in common code.

[aiidziis]

Ok, you are right it is called on background thread and this insert function is not blocking UI. Will investigate further what else might be blocking it. Thanks.

[Kris Wong]

is your UI trying to query at the same time the insert is happening?

[aiidziis]

Turns out I wasn’t performing select from DB on Dispatchers.Default .

[aiidziis]

Was using flowOn(Dispatchers.Default) on Flow and thought that it would make select on Dispatchers.Default .