Thread: Re: [DOCS] Use of 'now'

> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> >> Nothing of interest anymore, since 'current' has been removed as of 7.2.
> >> However, Thomas has yet to commit any docs updates for his recent
> >> datetime-related changes ... including that one ...
>
> > Seems it is still in there somewhere:
>
> >     test=> create table bb (x timestamp default 'current', y int);
>
> Hmm.  It was *supposed* to be removed entirely, but possibly what
> Thomas actually did was to continue to accept the keyword as equivalent
> to 'now'.  Thomas?

[ CC'ing to hackers because this is getting into code problems. ]

Here's another inconsistency that Tatsuo found:

    test=> create table ff (x time default 'current_timestamp');
    ERROR:  Bad time external representation 'current_timestamp'
    test=> create table ff (x time default 'current');
    ERROR:  Bad time external representation 'current'
    test=> create table ff (x time default 'now');
    CREATE
    test=> select current_timestamp;
              timestamptz
    -------------------------------
     2001-11-13 22:49:50.607401-05
    (1 row)

You can default a time to now, but not to current or current_timestamp.

I believe this is happening because current is implemented as special
timezones in datetime.c and timestamp.c, and current_timestamp is
implemented in gram.y, while 'now' is a function.

Anyway, looks like confusion that should be fixed.

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> [ CC'ing to hackers because this is getting into code problems. ]

Not sure I agree with that conclusion yet.

> Here's another inconsistency that Tatsuo found:
>         test=> create table ff (x time default 'current_timestamp');
>         ERROR:  Bad time external representation 'current_timestamp'

Never was a feature, and not documented as such. CURRENT_TIMESTAMP (and
CURRENT_DATE and CURRENT_TIME; note lack of quotes) are defined by SQL9x
as specialty constants (they have some other term for them afaicr).

>         test=> create table ff (x time default 'current');
>         ERROR:  Bad time external representation 'current'

Never was a feature, but sure seems like it should have been. How have
we missed all of those complaints about this over the last six years? ;)
We'll guess that 'current' was not one of the most utilized features of
the date/time types (which is one reason why I supported removing it).

>         test=> create table ff (x time default 'now');
>         CREATE
>         test=> select current_timestamp;
>                   timestamptz
>         -------------------------------
>          2001-11-13 22:49:50.607401-05
>         (1 row)
>
> You can default a time to now, but not to current or current_timestamp.
>
> I believe this is happening because current is implemented as special
> timezones in datetime.c and timestamp.c, and current_timestamp is
> implemented in gram.y, while 'now' is a function.

Not sure what special time zones have to do with it (did you mean
"special timestamps"?). CURRENT_xxx has to be implemented in gram.y
since they are keywords, not quoted strings. 'now' is not a function,
though now() is; both 'now' and 'current' are special cases in the input
parser for the date/time data types, with one inconsistancy as noted
above. That will be fixed.

> Anyway, looks like confusion that should be fixed.

The documentation covers some of this, and Tom has pointed out
(presumably to encourage a contribution) that it hasn't been updated yet
for the most recent changes for 7.2. I expect to do so in the next
couple of weeks.

                      - Thomas