Enable storing NULL in database

[Vlastimil Zíma]

Hi everybody,

I know this was here before, but it is really a problem. We need (I literally mean need, not just want) a simple way to store NULL in database instead of ''. Using empty string has several serious consequences (in databases which distinguishes between NULL and '', which are to my knowledge all but oracle).

 * You can't make a model with unique optional field. Django admin will let you store only one object without the value, because others with conflict the unique constraint.
 * It is useless to set NOT NULL constraints on text fields. Because Django stores empty string as empty value, database will not complain about invalid data and just stores the rubbish.

I don't want to enforce anybody to use only NULL as empty value, I just want Django to store NULL in database when I told it to. And I don't mean the way of overriding all the form fields as I have to now.

Regards,
Vlastimil

[Elyézer Rezende]

Setting null=True in the field definition and doing model.field = None doesn't do this?

If you create a gist or a paste with a sample code would help understand better.

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Elyézer Rezende
http://elyezer.com

[Karen Tracey]

On Thu, Nov 7, 2013 at 5:37 AM, Vlastimil Zíma <vlas...@ziima.cz> wrote:

I don't want to enforce anybody to use only NULL as empty value, I just want Django to store NULL in database when I told it to. And I don't mean the way of overriding all the form fields as I have to now.

A concrete proposal would help here.

[Aymeric Augustin]

2013/11/7 Elyézer Rezende <elye...@gmail.com>

Setting null=True in the field definition and doing model.field = None doesn't do this?

At the model layer, yes.

But if you're using a ModelForm — like the admin does — then you need some code to convert empty strings to None. I believe that's the problem Vlastimil wants to solve.

--
Aymeric.

[Elyézer Rezende]

On Thu, Nov 7, 2013 at 10:59 AM, Aymeric Augustin <aymeric....@polytechnique.org> wrote:

But if you're using a ModelForm — like the admin does — then you need some code to convert empty strings to None. I believe that's the problem Vlastimil wants to solve.

Got it.

Thanks for the clarification. 

[Vlastimil Zíma]

Augustin's correct :)

If I could suggest a solution, I would like to have a `null=False` argument on form fields. I believe this would fix the problems noted above and be sort of backwards-compatible. When using model forms, the argument would be set according to the `null` attribute of the respective model field.

Other version of this is a argument like `empty_value=''` which would allow more variability, though I'm not sure if it's needed.

I am not quite sure if there are completely unrelated places where Django uses hardcoded empty string as a empty value. That would be a problem.

What do you think?

Vlastimil

Dne čtvrtek, 7. listopadu 2013 13:55:54 UTC+1 Karen Tracey napsal(a):

[Alessandro Pagnin]

I had the same problem to solve, and I made this app to solve the problem https://github.com/alepane21/django-nullablecharfield.

On the "widget level" it adds to the right of the field a checkbox to click to set the value to None/NULL.

[Vlastimil Zíma]

Alesandro: Thanks for link, but this does not quite solve the issue.

1. I don't want user to decide how data gets stored in database. That's my (developer) decision.
2. There are other text fields which stores data as text in database - e.g. URLField and even the FileField.

Vlastimil

Dne sobota, 9. listopadu 2013 10:49:40 UTC+1 Alessandro Pagnin napsal(a):