Error when rolling back transaction after performing only a SELECT query

[sanmadjack]

When I run this code:

Future _putMethod(RestRequest request) {
  return this._pool.startTransaction().then((mysql.Transaction tran) {
    return tran.prepare("SELECT * FROM files").then((mysql.Query query) {
      return query.execute().then((result) {
        // Do something?
      }).then((_) {
        this._log.info("Closing");
        query.close();
      });
    }).then((_) {
      this._log.info("Rolling");
      return tran.rollback().then((_) {
        this._log.info("Rolled");
      });
    });
  });
}

I get this output:

2014-07-04 14:35:46.528: INFO: (ConnectionPool) Starting transaction
2014-07-04 14:35:46.572: INFO: (FilesResource) Closing
2014-07-04 14:35:46.573: INFO: (FilesResource) Rolling
2014-07-04 14:35:46.574: SEVERE: (RestServer) MySQL Client Error: Connection #0 cannot process a request for Instance of '_QueryStreamHandler' while a request is already in progress for Instance of '_ExecuteQueryHandler'
Uncaught Error: Bad state: Future already completed
Stack Trace:
#0 _AsyncCompleter.completeError (dart:async/future_impl.dart:35)
#1 _handleData (package:sqljocky/src/connection.dart:211:31)
#2 _rootRunUnary (dart:async/zone.dart:730)
#3 _RootZone.runUnary (dart:async/zone.dart:864)
#4 _Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:488)
#5 _Future._propagateToListeners (dart:async/future_impl.dart:571)
#6 _Future._completeWithValue (dart:async/future_impl.dart:331)
#7 _Future._asyncComplete. (dart:async/future_impl.dart:393)
#8 _asyncRunCallbackLoop (dart:async/schedule_microtask.dart:23)
#9 _asyncRunCallback (dart:async/schedule_microtask.dart:32)
#10 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:128)

Am I doing something wrong?

[sanmadjack]

Just fyi, this is a simplified example of how to reproduce the issue. In reality my process should run update and insert statements, but I noticed this happening if an error occurs before actually writing anything.

[sanmadjack]

If I remove the query execute, like below, it completes without error.

Future _putMethod(RestRequest request) {
  return this._pool.startTransaction().then((mysql.Transaction tran) {
    return tran.prepare("SELECT * FROM files").then((mysql.Query query) {
    }).then((_) {
      this._log.info("Rolling");
      return tran.rollback().then((_) {
        this._log.info("Rolled");
      });
    });
  });
}

[sanmadjack]

I discovered that if I do something to complete the result object's stream, this error does not occur. for instance:

Future _putMethod(RestRequest request) {
  return this._pool.startTransaction().then((mysql.Transaction tran) {
    return tran.prepare("SELECT name FROM files").then((mysql.Query query) {
      return query.execute().then((result) {
        return result.toList();
        // Do something?
      }).then((_) {
        _log.info("Closing");
        query.close();
      });
    }).then((_) {
      _log.info("Rolling");
      return tran.rollback().then((_) {
        _log.info("Rolled");
      });
    });
  });
}

running result.toList() causes the result object to finish its stream, after which the transaction can be rolled back without issue.

[jamesots]

Not fixed properly - need to do more work on this.