On Mon, Mar 16, 2009 at 11:52 AM, koranthala <koranth...@gmail.com> wrote:
>
>
>
> On Mar 16, 8:14 pm, Alex Gaynor <alex.gay...@gmail.com> wrote:
> > On Mon, Mar 16, 2009 at 11:07 AM, koranthala <koranth...@gmail.com>
> wrote:
> >
> > > Hi,
> > > I downloaded Django 1.1 due to aggregation support.
> > > But I am facing one issue which I cannot seem to overcome.
> > > I have two fields which represents two different times.
> > > I want to get the sum of difference of times - and I am unable to
> > > do so.
> > > Basically, I want to do as follows:
> > > SELECT SUM (time2 - time1) FROM _TABLE_ WHERE __XXX___
> >
> > > I tried 2 options:
> > > 1. self.filter( XXX).aggregate(diff=Sum('time2 - time1'))
> > > 2. self.filter (XXX).aggregate(t2=Sum('time2'), t1= Sum('time1')) - so
> > > that I can do t2 - t1 later.
> >
> > > Both is not supported in Django. I have raw SQL code in model
> > > Manager for the same. I thought using Django Aggregation is better. Is
> > > such operations going to be supported in Django 1.1 ?
> >
> > > Regards
> > > Koran
> >
> > Right now that isn't possible, is there any reason you couldn't just
> bring
> > the seperate SUMs into python and do the subtraction there, I realize it
> > isn't quite as clean but the overhead should be minimal?
> >
> > Alex
> >
> > --
> > "I disapprove of what you say, but I will defend to the death your right
> to
> > say it." --Voltaire
> > "The people's good is the highest law."--Cicero
>
> If I understand correctly:
> Separate SUMs as in the 2nd option which I mentioned above?
> It was not possible because currently aggregation methods does not
> support SUM - I think because Python itself does not support SUM of
> datetime objects.
>
> Or was it:
> Separate SUM as in bring all the tuples to Python and then calculate?
> It is quite big because there are more than 1 Million tuples so I dont
> want to bring everything to Python.
>
> Please let me know whether I have understood correctly.
> >
>
Sorry, I missed that these were dates/times. Right now there isn't complete
support for aggregating on dates/times. I think here the easiest route is
just to do:
self.extra(select={'diff': "SUM(field1-field2"}).values('diff')
Which I believe will work.
Alex
--
"I disapprove of what you say, but I will defend to the death your right to
say it." --Voltaire
"The people's good is the highest law."--Cicero
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