// EncodeDecimal encodes a decimal d into a byte slice which can be sorted lexicographically later.
func EncodeDecimal(b []byte, d types.Datum) []byte {
dec := d.GetMysqlDecimal()
precision := d.Length()
frac := d.Frac()
if precision == 0 {
precision, frac = dec.PrecisionAndFrac()
}
b = append(b, byte(precision), byte(frac))
bin, err := dec.ToBin(precision, frac)
if err != nil {
log.Errorf("should not happen, precision %d, frac %d %v", precision, frac, err)
return b
}
b = append(b, bin...)
return b
}