Re: Proposed patch: make SQL interval-literal syntax work per spec

Tom Lane wrote:
> Ron Mayer <rm_pg@cheapcomplexdevices.com> writes:
>> Back a while ago (2003) there was some talk about replacing
>> some of the non-standard extensions with shorthand forms of
>> intervals with ISO 8601 intervals that have a similar but
>> not-the-same shorthand.
> 
> I think *replacement* would be a hard sell, as that would tick off all
> the existing users ;-).  Now it seems like being able to accept either

I originally submitted a patch that supported both, and I think
you suggested replacing on the grounds that the old one was
never documented,

http://archives.postgresql.org/pgsql-patches/2003-09/msg00134.php "If we're going to support the real ISO spec, I'd
suggestripping  out any not-quite-there variant.
 

http://archives.postgresql.org/pgsql-patches/2003-09/msg00121.php "I doubt anyone is using it, because it's completely
undocumented."

On the other hand, the company I was at was indeed originally
using it, so I prefer that it stay in as well.   Perhaps if
there's a way to mark them as deprecated and post warnings in
the log file if they're used.   I think they should be
removed eventually in a few releases, because they're quite
confusing as they stand:
     Interval            ISO             Postgres                         8601            shorthand
-----------------------------------------------------    '1 year 1 minute'   'P1YT1M'         '1Y1M'     '1 year 1
month'   'P1Y1M'          N/A
 


> the 8601 syntax or the existing syntaxes on input wouldn't be tough
> at all, if you insist on the P prefix to distinguish; so that end of

ISO 8601 seems to me to require the P, so I think we would.

> it should be easy enough.  On the output side, seems like a GUC variable
> is the standard precedent here.  I'd still vote against overloading
> DateStyle --- it does too much already --- but a separate variable for
> interval style wouldn't bother me.  In fact, given that we are now
> somewhat SQL-compliant on interval input, a GUC that selected
> PG traditional, SQL-standard, or ISO 8601 interval output format seems
> like it could be a good idea.

Great.  I'm bringing my patch up-to-date with CVS now
and adding the separate GUC.