Re: [HACKERS] date_part()/EXTRACT(second) behaviour with time data type

Gregory Stark <stark@xxxxxxx> writes:
> I think we broke date_part for extracting seconds from time arguments. It
> appears we leave out the milliseconds whereas we don't for timestamp
> arguments. This was not the case in 8.3 where we included the milliseconds for
> both data types.

It's not new.  This appears to be a difference between the integer and
float timestamp code paths, and I'd say it's probably a thinko:

            case DTK_SECOND:
#ifdef HAVE_INT64_TIMESTAMP
                result = tm->tm_sec + fsec / USECS_PER_SEC;
#else
                result = tm->tm_sec + fsec;
#endif
                break;

In the integer case, fsec is an integer and so the division loses the
fraction.  timestamptz_part does this instead:

            case DTK_SECOND:
#ifdef HAVE_INT64_TIMESTAMP
                result = tm->tm_sec + fsec / 1000000.0;
#else
                result = tm->tm_sec + fsec;
#endif
                break;

I agree that we should change it, but should we back-patch it, and if so
how far?

                        regards, tom lane

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