On Mar 16, 11:44 pm, Alex Gaynor <alex.gay...@gmail.com> wrote:
> 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
Thank you very much Alex.
I wrote the raw SQL code yesterday - took me about >1 hr to get it
correct (it was quite a complex one). :-(
But this seems to be much MUCH easier.
Thank you again. I will work using this method.
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