driver/connector.go
func (c *Connector) FetchSize() int {
	c.mu.RLock()
	defer c.mu.RUnlock()
	return c.fetchSize
}
func (c *Connector) FetchSize() int {
	c.mu.RLock()
	defer c.mu.RUnlock()
	return c.fetchSize
}
// FetchSize returns the fetchSize of the connector.