SQLite Serialized Mode - xamarin.android

Question

I have an Xamarin Android project and was using mono.data.sqlite and had problems with multithreading, so I tried the Zumero component. I'm still having problems. I'm trying to set serialized mode as with the flag SQLITE_CONFIG_SERIALIZED in http://www.sqlite.org/threadsafe.html. I'm still getting random crashes. Can I set the serialized flag with Zumero? Any other suggestions other than recompiling SQLite from the source?
Thanks,
Brian

Answer 1

I used to have this problem. And despite conflicting recommendations here's how I stopped getting the exceptions:
Share a static instance of SQLiteConnection between all threads. This is safe to do as SQLite connection is only a file pointer it's not like a traditional data connection.
Wrapped all my SQLite queries/inserts/updates in a mutex with the statix instance of my SQLiteConnection as the lock. I've been advised that I shouldn't need to do this when using serialized mode however my experience with it begs to differ.
lock(myStaticConnection) {
myStaticConnection.Query<Employee>("....");
}
As a backup I also use some added retry logic to encapsulate every query. Not sure if SQLite does this on its own (I've seen reference to busytimeout and people claiming it is now gone?). Something like this:
public static List<T> Query<T> (string query, params object[] args) where T : new()
{
return Retry.DoWithLock (() => {
return Data.connection.Query<T> (query, args);
}, Data.connection, 0);
}
public static T DoWithLock<T>(
Func<T> action,
object lockable,
long retryIntervalTicks = defaultRetryIntervalTicks,
int retryCount = defaultRetryCount)
{
return Do (() => {
lock (lockable) {
return action();
}
});
}
public static T Do<T>(
Func<T> action,
long retryIntervalTicks = defaultRetryIntervalTicks,
int retryCount = defaultRetryCount)
{
var exceptions = new List<Exception> ();
for (int retry = 0; retry < retryCount; retry++) {
try{
return action();
} catch (Exception ex) {
exceptions.Add (ex);
ManualSleepEvent (new TimeSpan(retryIntervalTicks));
}
}
throw new AggregateException (exceptions);
}