Historically, extract() just returned zero for any case involving an
infinite timestamp[tz] input; even cases in which the unit name was
invalid. This is not very sensible. Instead, return infinity or
-infinity as appropriate when the requested field is one that is
monotonically increasing (e.g, year, epoch), or NULL when it is not
(e.g., day, hour). Also, throw the expected errors for bad unit names.
BACKWARDS INCOMPATIBLE CHANGE
Vitaly Burovoy, reviewed by Vik Fearing
the timestamp types. Turns out this doesn't even reduce the available
range of dates, since the restriction to dates that work for Julian-date
arithmetic is much tighter than the int32 range anyway. Per a longstanding
TODO item.
> why does CVS tip still give me
>
> regression=# select extract(century from now());
> date_part
> -----------
> 20
> (1 row)
> [ ... looks in code ... ]
>
> Apparently it's because you fixed only timestamp_part, and not
> timestamptz_part. I'm not too sure about what timestamp_trunc or
> timestamptz_trunc should do, but they may be wrong as well.
Sigh... as usual, what is not tested does not work:-(
> Could we have a more complete patch?
Please find a submission attached. I hope it really fixes all decade,
century and millenium issues for extract and *_trunc functions on
interval
and other timestamp types. If someone could check that the results
are reasonnable, it would be great.
I indeed overlooked the fact that there were two functions. The patch
fixes the code so that both variants agree.
I added comments to interval extractions, because it relies on the C
division to have a negative remainder: -7/10 = 0 and remains -7.
As for *_trunc functions, I have chosen to put the first year of the
century or millennium: -100, 1, 101... 1001 2001 etc. Indeed, I don't
think it would make sense to put 2000 (last year of the 2nd millennium)
for rounding all years of the third millenium.
I also fixed the code so that all decades last 10 years and decade 199
means the 1990's.
I have added some tests that are relevant to deal with tricky cases. The
formula may be simplified, but all these cases must pass. Please keep
them.
Fabien Coelho
"millennium" date part implementation in postgresql, both in the code
and the documentation, so that it conforms to the official definition.
If you do not agree with the official definition, please send your
complaint to "pope@vatican.org". I'm not responsible for them;-)
With the previous version, the centuries and millenniums had a wrong
number and started the wrong year. Moreover century number 0, which does
not exist in reality, lasted 200 years. Also, millennium number 0 lasted
2000 years.
If you want postgresql to have it's own definition of "century" and
"millennium" that does not conform to the one of the society, just give
them another name. I would suggest "pgCENTURY" and "pgMILLENNIUM";-)
IMO, if someone may use the options, it means that postgresql is used for
historical data, so it make sense to have an historical definition. Also,
I just want to divide the year by 100 or 1000, I can do that quite easily.
BACKWARD INCOMPATIBLE CHANGE
Fabien Coelho - coelho@cri.ensmp.fr
which had been unintentionally broken by recent changes to tighten up the
DateStyle rules for all-numeric date input. Add documentation and
regression tests for this, too.
Tom Lane
Bruce Momjian
Thomas G. Lockhart