Re: How to add explicit types so I can use OVERLAPS?

Il giorno ven, 01/08/2008 alle 14.47 +0000, Matthew Wilson ha scritto:
> I want to use the OVERLAPS keyword to compare two time intervals, but
> I'm having trouble.
> 
> In the code below, I want to test if the time interval from 9:15 AM
> through 9:45 AM overlaps the time interval from 8 AM through 10 AM.
> 
> This approach fails:
> 
>     >>> d = {'9:15 AM':datetime(2008, 8, 1, 9, 15),
>     ...      '9:45 AM':datetime(2008, 8, 1, 9, 45),
>     ...      '8 AM':datetime(2008, 8, 1, 8),
>     ...      '10 AM':datetime(2008, 8, 1, 10)}
> 
>     >>> cursor.execute('select (%(9:15 AM)s, %(9:45 AM)s) '
>     ...                'overlaps (%(8 AM)s, %(10 AM)s);', d)
> 
>     ------------------------------------------------------------
>     Traceback (most recent call last):
>       File "<ipython console>", line 1, in <module>
>     ProgrammingError: function pg_catalog.overlaps(unknown, unknown,
>     unknown, unknown) is not unique
>     LINE 1: ...ct ('2008-08-01T09:15:00', '2008-08-01T09:45:00') overlaps
>     (...
>                                                                  ^
>     HINT:  Could not choose a best candidate function. You might need to add
>     explicit type casts.
> 
> Meanwhile, this approach works fine:
> 
>     >>> cursor.execute('select (TIMESTAMP %(9:15 AM)s, TIMESTAMP %(9:45 AM)s) '
>                        'overlaps (TIMESTAMP %(8 AM)s, TIMESTAMP %(10 AM)s);', d)
> 
>     >>> cursor.fetchall()
>     [(True,)]
> 
> For a lot of boring reasons, I don't want to go into all my code and add
> the TIMESTAMP cast.
> 
> Is there anything else possible?

This is PostgreSQL 8.3 not automatically casting anymore. We should
probably change some of the getquoted() methods of the adapters to make
sure they add a (backend) typecast. And yes, patches are welcome.

federico

-- 
Federico Di Gregorio                         http://people.initd.org/fog
Debian GNU/Linux Developer                                [email protected]
INIT.D Developer                                           fog-NGVKUo/i/[email protected]
 heisenbug /hi:'zen-buhg/ /n./ [from Heisenberg's Uncertainty Principle
  in quantum physics] A bug that disappears or alters its behavior when
  one attempts to probe or isolate it.

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