public void updateBy(String outputTableId, Expression onUpdateExpression) {

        this.outputStream = new UpdateStream(outputTableId, CURRENT_EVENTS, onUpdateExpression);
    }
Method to set an updateStream as the outputStream of the on-demand query

@param outputTableId      id of the table which is going to be queried
@param onUpdateExpression expression for the update operation defined in the on-demand query
modules/siddhi-query-api/src/main/java/io/siddhi/query/api/execution/query/OnDemandQuery.java