Increment a value in a database table field

[Denis Bahati]

Hi All,

I have a field with an integer value which needs to be incremented
every time any user updates its status within a week. If that week has
passed it should insert a new row. Now i was trying to figure out but
didn't get any concept on how to go through. Please any idea?

[scot....@gmail.com]

You don't mention how you're tracking dates or weeks (is that a
related model, or... ?) but this would be the general idea:

- get the timestamp of the last update to that field and compare it to
the current timestamp

if ... : # interval is less than a week:
foo = MyModel.objects.get(...)
foo.counter = foo.counter + 1
else : interval is more than a week
foo = MyModel()
foo.counter = 1

foo.save()

[Denis Bahati]

Hi,

Here is my model am using to update items status.

 

class User(models.Model)
            users = models.ForeignKey(User)

            resources = models.ForeignKey(Resource)

           date_tracked = models.DateTimeField('Date Tracked')

           description = models.TextField()

           status_count_per_week = models.IntegerField()

status = models.ForeignKey(Status)

class Meta:

verbose_name_plural = 'Track Resources'

What i want to achieve is that:

  When i update the status the item first i should get the date last tracked and compare with tje current date, if the date tracked and the current date are not in the same week it should insert into a new row of status_count_per_week. If the date tracked and the current date are in the same week it should increment the value of status_count_per_week .

Regards.

Denis.
 

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[Karen Tracey]

On Sat, Nov 14, 2009 at 10:25 AM, Denis Bahati <djm...@gmail.com> wrote:

Hi,

Here is my model am using to update items status.

 

class User(models.Model)
            users = models.ForeignKey(User)

            resources = models.ForeignKey(Resource)

           date_tracked = models.DateTimeField('Date Tracked')

           description = models.TextField()

           status_count_per_week = models.IntegerField()

status = models.ForeignKey(Status)

class Meta:

verbose_name_plural = 'Track Resources'

What i want to achieve is that:

  When i update the status the item first i should get the date last tracked and compare with tje current date, if the date tracked and the current date are not in the same week it should insert into a new row of status_count_per_week. If the date tracked and the current date are in the same week it should increment the value of status_count_per_week .

I find your model and description confusing -- I am not sure the model you have defined is correct for what you want to achieve -- so I am not going to attempt to craft a solution exactly. Instead I'll point you to the two building blocks I think you need to achieve what you are looking for.  First, get_or_create:

http://docs.djangoproject.com/en/dev/ref/models/querysets/#get-or-create-kwargs

which you can use to either get the model containing a specific set of fields or create it if it does not exist.

Second, update() with an F() expression can be used to atomically increment a counter:

http://docs.djangoproject.com/en/dev/ref/models/instances/#updating-attributes-based-on-existing-fields

Karen

 

[Denis Bahati]

Exactly Karen the model is confusing. Here is the exactly model.

class Resource_Track(models.Model)
            users = models.ForeignKey(User)

            resources = models.ForeignKey(Resource)

            date_tracked = models.DateTimeField('Date Tracked')

            description = models.TextField()

            status_count_per_week = models.IntegerField()

            status = models.ForeignKey(Status)

            class Meta:

               verbose_name_plural = 'Track Resources'

Sorry for confusing you.
Regards
Denis.

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