Race condition in `PsSqlDriver`?

[ecstatic-morse]

I'm seeing intermittent crashes involving PsSqlDriver, for example

inside fireTableUpdates

     Fatal Exception: java.lang.ArrayIndexOutOfBoundsException: length=7; index=7
       at java.util.LinkedHashMap.keysToArray(LinkedHashMap.java:703)
       at java.util.LinkedHashMap.keysToArray(LinkedHashMap.java:691)
       at java.util.HashSet.toArray(HashSet.java:376)
       at java.util.ArrayList.<init>(ArrayList.java:188)
       at kotlin.collections.CollectionsKt___CollectionsKt.toMutableList(_Collections.kt:1343)
       at kotlin.collections.CollectionsKt___CollectionsKt.toList(_Collections.kt:1324)
       at com.powersync.PsSqlDriver.fireTableUpdates(PsSqlDriver.kt:37)
       at com.powersync.DatabaseDriverFactory.onTransactionCommit(DatabaseDriverFactory.android.kt:29)
       at io.requery.android.database.sqlite.SQLiteConnection.nativeExecuteForChangedRowCount(SQLiteConnection.java)
       at io.requery.android.database.sqlite.SQLiteConnection.executeForChangedRowCount(SQLiteConnection.java:778)
       at io.requery.android.database.sqlite.SQLiteSession.executeForChangedRowCount(SQLiteSession.java:764)
       at io.requery.android.database.sqlite.SQLiteStatement.executeUpdateDelete(SQLiteStatement.java:71)
       at app.cash.sqldelight.driver.android.AndroidPreparedStatement.execute(AndroidSqliteDriver.kt:261)
       at app.cash.sqldelight.driver.android.AndroidSqliteDriver$execute$2.invoke(AndroidSqliteDriver.kt:184)
       at app.cash.sqldelight.driver.android.AndroidSqliteDriver$execute$2.invoke(AndroidSqliteDriver.kt:184)
       at app.cash.sqldelight.driver.android.AndroidSqliteDriver.execute-zeHU3Mk(AndroidSqliteDriver.kt:169)
       at app.cash.sqldelight.driver.android.AndroidSqliteDriver.execute(AndroidSqliteDriver.kt:184)
       at com.powersync.PsSqlDriver.execute(:7)
       at com.powersync.db.internal.InternalDatabaseImpl.execute(InternalDatabaseImpl.kt:85)
       at com.powersync.db.PowerSyncDatabaseImpl.execute(PowerSyncDatabaseImpl.kt:235)
       at com.ravenscarlabs.yingyu.powersync.SyncedDatabase$execute$2.invokeSuspend(SyncedDb.kt:140)
       at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
       at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)
       at kotlinx.coroutines.internal.LimitedDispatcher$Worker.run(LimitedDispatcher.kt:113)
       at kotlinx.coroutines.scheduling.TaskImpl.run(Tasks.kt:89)
       at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:586)
       at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:820)
       at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:717)
       at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:704)

and

inside toFriendlyTableName (whose argument comes from PsSqlDriver)

          Fatal Exception: java.lang.NullPointerException: Parameter specified as non-null is null: method kotlin.text.Regex.containsMatchIn, parameter input
       at kotlin.text.Regex.containsMatchIn(:2)
       at com.powersync.db.internal.InternalDatabaseImpl.toFriendlyTableName(InternalDatabaseImpl.kt:203)
       at com.powersync.db.internal.InternalDatabaseImpl.access$toFriendlyTableName(InternalDatabaseImpl.kt:24)
       at com.powersync.db.internal.InternalDatabaseImpl$1$2.emit(InternalDatabaseImpl.kt:71)
       at com.powersync.db.internal.InternalDatabaseImpl$1$2.emit(InternalDatabaseImpl.kt:70)
       at kotlinx.coroutines.flow.FlowKt__DelayKt$debounceInternal$1$3$1.invokeSuspend(Delay.kt:226)
       at kotlinx.coroutines.flow.FlowKt__DelayKt$debounceInternal$1$3$1.invoke(:8)
       at kotlinx.coroutines.flow.FlowKt__DelayKt$debounceInternal$1$3$1.invoke(:2)
       at kotlinx.coroutines.selects.SelectImplementation$ClauseData.invokeBlock(Select.kt:843)
       at kotlinx.coroutines.selects.SelectImplementation.complete(Select.kt:715)
       at kotlinx.coroutines.selects.SelectImplementation.doSelectSuspend(Select.kt:456)
       at kotlinx.coroutines.selects.SelectImplementation.access$doSelectSuspend(Select.kt:251)
       at kotlinx.coroutines.selects.SelectImplementation$doSelectSuspend$1.invokeSuspend(:13)
       at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
       at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)
       at kotlinx.coroutines.internal.LimitedDispatcher$Worker.run(LimitedDispatcher.kt:113)
       at kotlinx.coroutines.scheduling.TaskImpl.run(Tasks.kt:89)
       at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:586)
       at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:820)
       at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:717)
       at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:704)
        

Operations on PsSqlDriver.pendingUpdates aren't thread-safe (it's a MutableSet), and I can't see any synchronization by callers that would make this correct:

powersync-kotlin/core/src/jvmMain/kotlin/com/powersync/DatabaseDriverFactory.jvm.kt

Lines 27 to 31 in 738fd0a

	val mappedDriver = PsSqlDriver(scope = scope, driver = driver)
	driver.connection.database.addUpdateListener { _, _, table, _ ->
	mappedDriver.updateTable(table)
	}

powersync-kotlin/core/src/commonMain/kotlin/com/powersync/db/internal/InternalDatabaseImpl.kt

Lines 106 to 110 in 738fd0a

	withContext(dbContext) {
	val r = executeSync(sql, parameters)
	driver.fireTableUpdates()
	r
	}

[michaelbarnes]

@ecstatic-morse thanks for bringing this to our attention. We'll take a look.