Slow date parsing #10942
Description
I'm investigating some performance degradation in some work I'm doing, and see time parsing (unrelated to the work I'm doing) light up as a christmas tree in the memory profiler:
flat flat% sum% cum cum%
2097170 13.54% 13.54% 2097170 13.54% time.cloneString (inline)
1409116 9.10% 22.64% 3506286 22.64% time.newParseErrorI guess this comes from the ineffective way of guessing the format in the upstream cast library:
func parseDateWith(s string, location *time.Location, formats []timeFormat) (d time.Time, e error) {
for _, format := range formats {
if d, e = time.Parse(format.format, s); e == nil {
// Some time formats have a zone name, but no offset, so it gets
// put in that zone name (not the default one passed in to us), but
// without that zone's offset. So set the location manually.
if format.typ <= timeFormatNamedTimezone {
if location == nil {
location = time.Local
}
year, month, day := d.Date()
hour, min, sec := d.Clock()
d = time.Date(year, month, day, hour, min, sec, d.Nanosecond(), location)
}
return
}
}
return d, fmt.Errorf("unable to parse date: %s", s)
}