SQLiteException: cannot start a transaction within a transaction

[Nek-12]

SQLiteException: cannot start a transaction within a transaction

[Lasombras]

fun foo() = runBlocking {
        async(Dispatchers.IO) {
            queries.transactionWithResult {
                 //Nothing
            }
        }

        async(Dispatchers.IO) {
            queries.transactionWithResult {
                 //Nothing
            }
        }
}

Just open 2 transactions in async and the driver raise this error.
It's like the driver try to run the transactions in a same thread and open a new transaction inside the first one.

Same with threads, just start 2 transactions in 2 threads, and the driver run the second transaction in the first one.

        thread {
            queries.transactionWithResult { }
        }

        thread {
            queries.transactionWithResult { }
        }
        Thread.sleep(500)

Exception in thread "Thread-6" org.sqlite.SQLiteException: [SQLITE_ERROR] SQL error or missing database (cannot start a transaction within a transaction)

In SQLDelight 2.0.0, to prevent this issue, I used a custom Dispatcher for my database request, limited to one parallelism.

        val databaseDispatcher = Dispatchers.IO.limitedParallelism(1)

        val table1Data = async(databaseDispatcher) { ... } 
        val table2Data = async(databaseDispatcher) { ... } 

But, of course, I break the parallelism of async in this temporary solution. And only one request can run at the same time.
I will return easily to the Dispatcher.IO when the fix will be done.

[AlecKazakova]

I'm not sure how this would result in nested transactions, is the method you're calling this from itself in a transaction?

Although SQLDelight does some protection from inner transactions (with the noEnclosing stuff) so that also surprised me. Are you able to make a repro project we can look in to?

[Nek-12]

Setting up a repro project would be a lot of work. If I have the free time, I can try to create one. No, the method itself is not in a transaction. This issue is reproduced in roughly 5% calls run

[Nek-12]

True, I am also still seeing this happening often still. Thanks, didn't expect the repro to be that simple

[Nek-12]

@AlecKazakova may I request this issue to be triaged? There is no more info to add and this issue currently affects a very large portion of our users in production

This issue alone has brought our project below the GP bad behavior threshold already

[DanielNovak]

It could be also a platform bug, but maybe triggered by SqlDelight. We have seen a similar bug in Room too.
Here is a link to the "platform bug":
https://issuetracker.google.com/issues/37001653