Grafana Alert in bigquery plugin


I have installed bigquery plugin(supplied by DoiT-International) for grafana to work on the bigquery datasets and tables. I can create graphs using the plugin. However I am not able to configure alerts using the said plugin. The alert query always stays true no matter what the underlying condition is and it never generates notifications.

Setting up grafana alert resulting in below error message.

"tsdb.HandleRequest() error Could not find executor for data source type: doitintl-bigquery-datasource"

Grafana : v6.1.3
Bigquery Plugin : DoiT-International

Could anyone suggest what is wrong here ?