do I need to run syncdb when I change the default value in a field of a model?

[Craig Schmidt]

This is probably an easy question, but I didn’t manage to find the answer.

If I just change the default value of a field in a model, do I need to run syncdb?

Specifically I changed:

foo = models.IntegerField(default=1)

to

foo = models.IntegerField(default=5)

Thanks,
Craig

[Shawn Milochik]

No, no syncdb required. The default applies to newly-created instances, not existing ones.

[Jonathan Baker]

Does that mean that the default="" functionality is implemented by the ORM, instead of in the database layer?

On Fri, Mar 14, 2014 at 5:16 PM, Shawn Milochik <shawn...@gmail.com> wrote:

No, no syncdb required. The default applies to newly-created instances, not existing ones.

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[Shawn Milochik]

On Fri, Mar 14, 2014 at 7:19 PM, Jonathan Baker <jonathand...@gmail.com> wrote:

Does that mean that the default="" functionality is implemented by the ORM, instead of in the database layer?

Perhaps I'm wrong -- I'm looking at my South migrations and they do pass the defaults. I believe that, either way, if you only touch the database through the ORM it'll be set properly. It probably depends on what database you're using.

However, there's a bigger issue -- if you run syncdb a second time, it will do nothing, so it doesn't matter either way. If you want to modify an existing table you need to use South (or do it manually). Syncdb will not touch existing tables -- it only adds new ones. Or you can wipe out your whole database and then run syncdb, that would fix it if you don't care about your data.

Shawn 

[Craig Schmidt]

In my case, it is for a system that isn’t in production yet, so I was planning to wipe the database before running syncdb.  I just didn’t know if that is necessary.

-Craig

Shawn 

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[Russell Keith-Magee]

On Sat, Mar 15, 2014 at 7:19 AM, Jonathan Baker <jonathand...@gmail.com> wrote:

Does that mean that the default="" functionality is implemented by the ORM, instead of in the database layer?

This is correct - Django's "default" argument is an API level default, not a database level default.

Yours,

Russ Magee %-) 

 

[Venkatraman S]

@Russ, any specific reasons for this choice?

Regards,

Venkat 

[Russell Keith-Magee]

Honestly - not a clue. It was like that when I got here, so the reasons are probably lost in the depths of time. :-)

Trying to reverse engineer the decision, the most likely reason is that Django has allowed callable defaults; if you define a callable in your Django model as a default, there's no way to pass this down to the database (or, at least, not an easy way). 

Yours,

Russ Magee %-) 

 

[Mike Dewhirst]

On 21/03/2014 11:13am, Russell Keith-Magee wrote:
>
> On Thu, Mar 20, 2014 at 6:50 PM, Venkatraman S <venk...@gmail.com
> <mailto:venk...@gmail.com>> wrote:
>
>
> On Sat, Mar 15, 2014 at 7:11 AM, Russell Keith-Magee
> <rus...@keith-magee.com <mailto:rus...@keith-magee.com>> wrote:
>
>
> On Sat, Mar 15, 2014 at 7:19 AM, Jonathan Baker
> <jonathand...@gmail.com

> <mailto:jonathand...@gmail.com>> wrote:
>
> Does that mean that the default="" functionality is
> implemented by the ORM, instead of in the database layer?
>
> This is correct - Django's "default" argument is an API level
> default, not a database level default.
>
>
> @Russ, any specific reasons for this choice?
>
>
> Honestly - not a clue. It was like that when I got here, so the reasons
> are probably lost in the depths of time. :-)

If some things are done in the database and some in the ORM, developer
madness ensues.

I think keeping everything in the ORM is entirely manageable for
programmers. Tweaking the database is last straw optimisation.

Mike

>
> Trying to reverse engineer the decision, the most likely reason is that
> Django has allowed callable defaults; if you define a callable in your
> Django model as a default, there's no way to pass this down to the
> database (or, at least, not an easy way).
>
> Yours,
> Russ Magee %-)
>

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[Venkatraman S]

This helped me in one of the cases just now and it was an Aha moment!  Never realized that this feature would be so darn useful. Thanks devs.

-V

@venkasub