Re: Generating a timeseries and aggregation/annotation using QuerySet.extra()

[Wannabe Coder]

Alright I get it now! Thanks for the clarification! From the looks of it, 
being able to manipulate lhs and rhs can cover a lot of possible SQL 
statements in a very reusable way, though it will still be nice to have 
that kind of transform/expression available out-of-the-box, since I think 
it is a common use case. Any idea if the Django team will include that?

-- 
You received this message because you are subscribed to the Google Groups 
"Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-users+unsubscr...@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at http://groups.google.com/group/django-users.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-users/6dc140e2-1e48-40c2-857a-cfc7ae25fcac%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

Re: Generating a timeseries and aggregation/annotation using QuerySet.extra()

[Wannabe Coder]

Alright I get it now! Thanks for the clarification! From the looks of it, 
being able to manipulate lhs and rhs can cover a lot of possible SQL 
statements in a very reusable way, though it will still be nice to have 
that kind of transform/expression available out-of-the-box, since I think 
it is a common use case. Any idea if the Django team will include that?

-- 
You received this message because you are subscribed to the Google Groups 
"Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-users+unsubscr...@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at http://groups.google.com/group/django-users.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-users/e2183b64-0cac-4e01-94f7-3ca2c4f266ca%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

Re: Generating a timeseries and aggregation/annotation using QuerySet.extra()

['Tom Evans' via Django users]

On Fri, Sep 11, 2015 at 1:15 PM, Wannabe Coder  wrote:
> Hello everyone!
>
> I already created a ticket detailing my use case, and one of the developers
> pointed me to this discussion group. I am not quite satisfied with the
> response I got since the DateTransforms that will be released in Django 1.9
> only appear to extract year/month/day/etc numbers and do not seem to be able
> to annotate based on generated time periods from a series of
> dates/datetimes. Basically what I can do with .extra() right now is generate
> a table like the ones shown in my screenshots.
>
> I hope that behavior would be possible to customize or even include in
> Django 1.9 out of the box. Thanks!

I think you have slightly misunderstood. The Expressions and Transform
API allows *you* to create user defined expressions and
transformations. Yes, there are some new built in expressions and
transformations available, but the real power is allowing you to
define such a transformation in a reusable way, rather than hacking it
in to extra() like you currently have to do in each place you want to
use it.

So you want an expression that is like MonthTransform, but using
DATE_TRUNC() instead of MONTH()? Have at it! It's a documented API:

https://docs.djangoproject.com/en/dev/ref/models/lookups/#transform-reference

The DB backends operations class even support a datetime_trunc_sql()
(compare with the implementation of DateTransform, base class of
MonthTransform)

https://github.com/django/django/blob/master/django/db/models/fields/__init__.py#L2432

Cheers

Tom

-- 
You received this message because you are subscribed to the Google Groups 
"Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-users+unsubscr...@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at http://groups.google.com/group/django-users.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-users/CAFHbX1KfNPY2mHUR3A1WtsrQ1qfJxKYnVFJb%3DQBTSgt2Om%2B%3D%2BQ%40mail.gmail.com.
For more options, visit https://groups.google.com/d/optout.

Generating a timeseries and aggregation/annotation using QuerySet.extra()

[Wannabe Coder]

Hello everyone!

I already created a ticket  
detailing my use case, and one of the developers pointed me to this 
discussion group. I am not quite satisfied with the response I got since 
the DateTransforms that will be released in Django 1.9 only appear to 
extract year/month/day/etc numbers and do not seem to be able to annotate 
based on generated time periods from a series of dates/datetimes. Basically 
what I can do with .extra() right now is generate a table like the ones 
shown in my screenshots.

I hope that behavior would be possible to customize or even include in 
Django 1.9 out of the box. Thanks!



-- 
You received this message because you are subscribed to the Google Groups 
"Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-users+unsubscr...@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at http://groups.google.com/group/django-users.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-users/796ec525-453e-4a04-892f-671744364fc5%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.