timePartMonth          = "MONTH"
	timePartDay            = "DAY"
	timePartHour           = "HOUR"
	timePartMinute         = "MINUTE"
	timePartSecond         = "SECOND"
	timePartTimezoneHour   = "TIMEZONE_HOUR"
	timePartTimezoneMinute = "TIMEZONE_MINUTE"
)

func extract(what string, t time.Time) (v *Value, err error) {
	switch what {
	case timePartYear:
		return FromInt(int64(t.Year())), nil
	case timePartMonth:

)

// ISO8601Format converts time 't' into ISO8601 time format expected in AWS S3 spec.
//
// This function is needed to avoid a Go's float64 precision bug, where Go avoids
// padding the extra '0' before the timezone.
func ISO8601Format(t time.Time) string {
	value := t.Format(iso8601TimeFormat)
	if len(value) < len(iso8601TimeFormat) {
		value = t.Format(iso8601TimeFormat[:len(iso8601TimeFormat)-1])

)

var DB *gorm.DB
var (
	mysqlDSN     = "gorm:gorm@tcp(localhost:9910)/gorm?charset=utf8&parseTime=True&loc=Local"
	postgresDSN  = "user=gorm password=gorm dbname=gorm host=localhost port=9920 sslmode=disable TimeZone=Asia/Shanghai"
	sqlserverDSN = "sqlserver://gorm:LoremIpsum86@localhost:9930?database=gorm"
	tidbDSN      = "root:@tcp(localhost:9940)/test?charset=utf8&parseTime=True&loc=Local"
)

func init() {
	var err error

		// take this server down, return appropriate error.
		if opts.Maintenance {
			writeResponse(w, http.StatusPreconditionFailed, nil, mimeNone)
		} else {
			writeResponse(w, http.StatusServiceUnavailable, nil, mimeNone)
		}
		return
	}
	writeResponse(w, http.StatusOK, nil, mimeNone)
}

// ClusterReadCheckHandler returns if the server is ready for requests.
func ClusterReadCheckHandler(w http.ResponseWriter, r *http.Request) {