Re: how to delete in the admin - strategy needed

[Mike Dewhirst]

Solved

I was culling children based on redundancy but a missing child was being 
automatically inserted again. The error was being correctly reported as 
a DoesNotExist problem but until I noticed the incremented pk in the 
database I was looking in the wrong places.


Thanks again for your effort - I'm sorry to waste your time.

Mike

On 6/02/2013 2:14pm, Mike Dewhirst wrote:

Pankaj, thank you

I have tried the code in a number of ways - including the way you wrote
it[1] - and located in either Master[2] or Parent and it always runs to
completion without raising its own exception. It happily prints out
progress flags in the dev server and then finally delivers the 500
ValidationError mentioned below.

My conclusion is the Admin doesn't like me.

My code (equivalent with yours) seems to be working but the entire
transaction seems to be getting rolled back when it is nearly finished.
I think it must be something to do with the data so I'm simplifying as
hard as I can and ...

I'm currently studying the traceback - which is *all* Django code and
none of mine.

More later

Thanks again.

Mike

[1] Your version was what I tried first because that is what the docs
illustrate. I eventually used the list to make sure the query_set
actually ran and I was deleting actual objects. I have now gone back to
the way you wrote it because I'm convinced the problem is elsewhere.

[2] It now lives in the Master and is called with the 'mark' from the
Parent on the pre-delete signal. I do this despite using pre-delete
because of the warning in docs about deleted objects trying to do
things. I know the Master won't be deleted.

On 6/02/2013 4:57am, Pankaj Singh wrote:

Hey Mike,

I tried to replicate what you were trying to do and I got it working.

By the way, you can directly delete filtered child objects, no need to
create a list. And you don't need to create a list for iterating over a
queryset.

Queryset supports iteration by
default(https://docs.djangoproject.com/en/dev/topics/db/queries/#querysets-are-lazy).


Here is models.py:


|from  django.dbimport  models
from  django.db.models.signalsimport  pre_delete
from  django.dispatchimport  receiver


class  Master(models.Model):
 name=  models.CharField(max_length=200)

 def  __unicode__(self):
 return  self.name


class  Parent(models.Model):
 name=  models.CharField(max_length=200)
 master=  models.ForeignKey(Master)
 mark=  models.CharField(max_length=40)

 def  __unicode__(self):
 return  self.name

 def  clean_out(self):
 Child.objects.filter(master=self.master,
tags=self.mark).delete()

 child_lst=  Child.objects.filter(master=self.master,
  tags__contains=self.mark)
 for  child in  child_lst:
 marks=  child.tags.split()
 marks.remove(self.mark)
 child.tags=  ''.join(marks)
 child.save()


class  Child(models.Model):
 name=  models.CharField(max_length=200)
 tags=  models.TextField()
 master=  models.ForeignKey(Master)

 def  __unicode__(self):
 return  self.name


@receiver(pre_delete,  sender=Parent)
def  parent_delete_handeler(sender,  instance,  *args,  **kwargs):
 instance.clean_out()|


Sincerely,
Pankaj Singh
http://about.me/psjinx


On Tue, Feb 5, 2013 at 12:15 PM, Mike Dewhirst mailto:mi...@dewhirst.com.au>> wrote:

Could someone please point out my mistake?

 def clean_out(self):
 child_lst = list(Child.objects.filter(__master=self.master,
   tags=self.mark))
 for child in child_lst:
 child.delete()

 child_lst = list(Child.objects.filter(__master=self.master,

tags__contains=self.mark))
 for child in child_lst:
 marks = child.tags.split()
 marks = marks.remove(self.mark)
 child.tags = ' '.join(marks)
 child.save()


The "self" in this case is an instance of the Parent class and
clean_out() is a Parent model method. Both Parent and Child have a
foreign key relationship with the Master model. Nothing has a
foreign key pointing to either Parent or Child.

Parent.clean_out() method is connected to the pre_delete signal of
the Parent model.

The purpose of the method is more or less documented below.

I've tried this a number of different ways and always get the
"Select a valid choice ..." error mentioned below.


On 4/02/2013 6:14pm, Mike Dewhirst wrote:

This is the error ... Select a valid choice. That choice is not
one of
the available choices.

I want to delete a bunch of "child" records when a "parent"
record is
deleted. While I'm using that terminology they are not actually
related
in the usual sense. All however are in foreign key relationships
with
the same owne

Re: how to delete in the admin - strategy needed

[Mike Dewhirst]

Pankaj, thank you

I have tried the code in a number of ways - including the way you wrote 
it[1] - and located in either Master[2] or Parent and it always runs to 
completion without raising its own exception. It happily prints out 
progress flags in the dev server and then finally delivers the 500 
ValidationError mentioned below.


My conclusion is the Admin doesn't like me.

My code (equivalent with yours) seems to be working but the entire 
transaction seems to be getting rolled back when it is nearly finished. 
I think it must be something to do with the data so I'm simplifying as 
hard as I can and ...


I'm currently studying the traceback - which is *all* Django code and 
none of mine.


More later

Thanks again.

Mike

[1] Your version was what I tried first because that is what the docs 
illustrate. I eventually used the list to make sure the query_set 
actually ran and I was deleting actual objects. I have now gone back to 
the way you wrote it because I'm convinced the problem is elsewhere.


[2] It now lives in the Master and is called with the 'mark' from the 
Parent on the pre-delete signal. I do this despite using pre-delete 
because of the warning in docs about deleted objects trying to do 
things. I know the Master won't be deleted.


On 6/02/2013 4:57am, Pankaj Singh wrote:

Hey Mike,

I tried to replicate what you were trying to do and I got it working.

By the way, you can directly delete filtered child objects, no need to
create a list. And you don't need to create a list for iterating over a
queryset.

Queryset supports iteration by
default(https://docs.djangoproject.com/en/dev/topics/db/queries/#querysets-are-lazy).

Here is models.py:


|from  django.dbimport  models
from  django.db.models.signalsimport  pre_delete
from  django.dispatchimport  receiver


class  Master(models.Model):
 name=  models.CharField(max_length=200)

 def  __unicode__(self):
 return  self.name


class  Parent(models.Model):
 name=  models.CharField(max_length=200)
 master=  models.ForeignKey(Master)
 mark=  models.CharField(max_length=40)

 def  __unicode__(self):
 return  self.name

 def  clean_out(self):
 Child.objects.filter(master=self.master,  tags=self.mark).delete()

 child_lst=  Child.objects.filter(master=self.master,
  tags__contains=self.mark)
 for  child in  child_lst:
 marks=  child.tags.split()
 marks.remove(self.mark)
 child.tags=  ''.join(marks)
 child.save()


class  Child(models.Model):
 name=  models.CharField(max_length=200)
 tags=  models.TextField()
 master=  models.ForeignKey(Master)

 def  __unicode__(self):
 return  self.name


@receiver(pre_delete,  sender=Parent)
def  parent_delete_handeler(sender,  instance,  *args,  **kwargs):
 instance.clean_out()|


Sincerely,
Pankaj Singh
http://about.me/psjinx


On Tue, Feb 5, 2013 at 12:15 PM, Mike Dewhirst mailto:mi...@dewhirst.com.au>> wrote:

Could someone please point out my mistake?

 def clean_out(self):
 child_lst = list(Child.objects.filter(__master=self.master,
   tags=self.mark))
 for child in child_lst:
 child.delete()

 child_lst = list(Child.objects.filter(__master=self.master,

tags__contains=self.mark))
 for child in child_lst:
 marks = child.tags.split()
 marks = marks.remove(self.mark)
 child.tags = ' '.join(marks)
 child.save()


The "self" in this case is an instance of the Parent class and
clean_out() is a Parent model method. Both Parent and Child have a
foreign key relationship with the Master model. Nothing has a
foreign key pointing to either Parent or Child.

Parent.clean_out() method is connected to the pre_delete signal of
the Parent model.

The purpose of the method is more or less documented below.

I've tried this a number of different ways and always get the
"Select a valid choice ..." error mentioned below.


On 4/02/2013 6:14pm, Mike Dewhirst wrote:

This is the error ... Select a valid choice. That choice is not
one of
the available choices.

I want to delete a bunch of "child" records when a "parent"
record is
deleted. While I'm using that terminology they are not actually
related
in the usual sense. All however are in foreign key relationships
with
the same owner/master.

The child records all know which parents they have because the
parent
added its mark to a field in the child when the child record got
created
and linked to the master. In fact if that child had been added by
another parent, the next parent just adds its mark instead of adding
another child.

  

Re: how to delete in the admin - strategy needed

[Pankaj Singh]

Hey Mike,

I tried to replicate what you were trying to do and I got it working.

By the way, you can directly delete filtered child objects, no need to
create a list. And you don't need to create a list for iterating over a
queryset.

Queryset supports iteration by default(
https://docs.djangoproject.com/en/dev/topics/db/queries/#querysets-are-lazy
).

Here is models.py:

from django.db import modelsfrom django.db.models.signals import
pre_deletefrom django.dispatch import receiver

class Master(models.Model):
name = models.CharField(max_length=200)

def __unicode__(self):
return self.name

class Parent(models.Model):
name = models.CharField(max_length=200)
master = models.ForeignKey(Master)
mark = models.CharField(max_length=40)

def __unicode__(self):
return self.name

def clean_out(self):
Child.objects.filter(master=self.master, tags=self.mark).delete()

child_lst = Child.objects.filter(master=self.master,
 tags__contains=self.mark)
for child in child_lst:
marks = child.tags.split()
marks.remove(self.mark)
child.tags = ' '.join(marks)
child.save()

class Child(models.Model):
name = models.CharField(max_length=200)
tags = models.TextField()
master = models.ForeignKey(Master)

def __unicode__(self):
return self.name

@receiver(pre_delete, sender=Parent)def parent_delete_handeler(sender,
instance, *args, **kwargs):
instance.clean_out()


Sincerely,
Pankaj Singh
http://about.me/psjinx


On Tue, Feb 5, 2013 at 12:15 PM, Mike Dewhirst wrote:

> Could someone please point out my mistake?
>
> def clean_out(self):
> child_lst = list(Child.objects.filter(**master=self.master,
>   tags=self.mark))
> for child in child_lst:
> child.delete()
>
> child_lst = list(Child.objects.filter(**master=self.master,
>   tags__contains=self.mark))
> for child in child_lst:
> marks = child.tags.split()
> marks = marks.remove(self.mark)
> child.tags = ' '.join(marks)
> child.save()
>
>
> The "self" in this case is an instance of the Parent class and clean_out()
> is a Parent model method. Both Parent and Child have a foreign key
> relationship with the Master model. Nothing has a foreign key pointing to
> either Parent or Child.
>
> Parent.clean_out() method is connected to the pre_delete signal of the
> Parent model.
>
> The purpose of the method is more or less documented below.
>
> I've tried this a number of different ways and always get the "Select a
> valid choice ..." error mentioned below.
>
>
> On 4/02/2013 6:14pm, Mike Dewhirst wrote:
>
>> This is the error ... Select a valid choice. That choice is not one of
>> the available choices.
>>
>> I want to delete a bunch of "child" records when a "parent" record is
>> deleted. While I'm using that terminology they are not actually related
>> in the usual sense. All however are in foreign key relationships with
>> the same owner/master.
>>
>> The child records all know which parents they have because the parent
>> added its mark to a field in the child when the child record got created
>> and linked to the master. In fact if that child had been added by
>> another parent, the next parent just adds its mark instead of adding
>> another child.
>>
>> When a parent gets deleted from the master, its mark is removed from all
>> the child records it was involved with and if it was the only mark the
>> child gets deleted too. Or at least that is what I want to happen.
>>
>> My question is:
>>
>> In overview, how should I be doing this?
>>
>> At the moment I'm trying to do it all via model methods calling various
>> managers because it feels like the right place to do it.
>>
>> I have tried to make a custom manager with use_for_related_fields = True
>> but still get the same error.
>>
>> Thanks for any help
>>
>> Mike
>>
>>
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Re: how to delete in the admin - strategy needed

[Mike Dewhirst]

Could someone please point out my mistake?

def clean_out(self):
child_lst = list(Child.objects.filter(master=self.master,
  tags=self.mark))
for child in child_lst:
child.delete()

child_lst = list(Child.objects.filter(master=self.master,
  tags__contains=self.mark))
for child in child_lst:
marks = child.tags.split()
marks = marks.remove(self.mark)
child.tags = ' '.join(marks)
child.save()


The "self" in this case is an instance of the Parent class and 
clean_out() is a Parent model method. Both Parent and Child have a 
foreign key relationship with the Master model. Nothing has a foreign 
key pointing to either Parent or Child.


Parent.clean_out() method is connected to the pre_delete signal of the 
Parent model.


The purpose of the method is more or less documented below.

I've tried this a number of different ways and always get the "Select a 
valid choice ..." error mentioned below.


On 4/02/2013 6:14pm, Mike Dewhirst wrote:

This is the error ... Select a valid choice. That choice is not one of
the available choices.

I want to delete a bunch of "child" records when a "parent" record is
deleted. While I'm using that terminology they are not actually related
in the usual sense. All however are in foreign key relationships with
the same owner/master.

The child records all know which parents they have because the parent
added its mark to a field in the child when the child record got created
and linked to the master. In fact if that child had been added by
another parent, the next parent just adds its mark instead of adding
another child.

When a parent gets deleted from the master, its mark is removed from all
the child records it was involved with and if it was the only mark the
child gets deleted too. Or at least that is what I want to happen.

My question is:

In overview, how should I be doing this?

At the moment I'm trying to do it all via model methods calling various
managers because it feels like the right place to do it.

I have tried to make a custom manager with use_for_related_fields = True
but still get the same error.

Thanks for any help

Mike



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Re: how to delete in the admin - strategy needed

[Mike Dewhirst]

On 4/02/2013 8:07pm, m1chael wrote:

I'll admit that i'm a bit old-school and most people are going to
cringe at seeing this,

I would set a DB trigger with the raw logic


I hadn't thought of that but I think it would be my last resort. I'd 
like to keep all the logic in one place. The answer has to be in a 
models.Manager somewhere. I guess I need to dig deeper.


Thanks

Mike







On Mon, Feb 4, 2013 at 2:14 AM, Mike Dewhirst  wrote:

This is the error ... Select a valid choice. That choice is not one of the
available choices.

I want to delete a bunch of "child" records when a "parent" record is
deleted. While I'm using that terminology they are not actually related in
the usual sense. All however are in foreign key relationships with the same
owner/master.

The child records all know which parents they have because the parent added
its mark to a field in the child when the child record got created and
linked to the master. In fact if that child had been added by another
parent, the next parent just adds its mark instead of adding another child.

When a parent gets deleted from the master, its mark is removed from all the
child records it was involved with and if it was the only mark the child
gets deleted too. Or at least that is what I want to happen.

My question is:

In overview, how should I be doing this?

At the moment I'm trying to do it all via model methods calling various
managers because it feels like the right place to do it.

I have tried to make a custom manager with use_for_related_fields = True but
still get the same error.

Thanks for any help

Mike

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Re: how to delete in the admin - strategy needed

[m1chael]

I'll admit that i'm a bit old-school and most people are going to
cringe at seeing this,

I would set a DB trigger with the raw logic





On Mon, Feb 4, 2013 at 2:14 AM, Mike Dewhirst  wrote:
> This is the error ... Select a valid choice. That choice is not one of the
> available choices.
>
> I want to delete a bunch of "child" records when a "parent" record is
> deleted. While I'm using that terminology they are not actually related in
> the usual sense. All however are in foreign key relationships with the same
> owner/master.
>
> The child records all know which parents they have because the parent added
> its mark to a field in the child when the child record got created and
> linked to the master. In fact if that child had been added by another
> parent, the next parent just adds its mark instead of adding another child.
>
> When a parent gets deleted from the master, its mark is removed from all the
> child records it was involved with and if it was the only mark the child
> gets deleted too. Or at least that is what I want to happen.
>
> My question is:
>
> In overview, how should I be doing this?
>
> At the moment I'm trying to do it all via model methods calling various
> managers because it feels like the right place to do it.
>
> I have tried to make a custom manager with use_for_related_fields = True but
> still get the same error.
>
> Thanks for any help
>
> Mike
>
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> "Django users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to django-users+unsubscr...@googlegroups.com.
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> For more options, visit https://groups.google.com/groups/opt_out.
>
>

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how to delete in the admin - strategy needed

[Mike Dewhirst]

This is the error ... Select a valid choice. That choice is not one of 
the available choices.


I want to delete a bunch of "child" records when a "parent" record is 
deleted. While I'm using that terminology they are not actually related 
in the usual sense. All however are in foreign key relationships with 
the same owner/master.


The child records all know which parents they have because the parent 
added its mark to a field in the child when the child record got created 
and linked to the master. In fact if that child had been added by 
another parent, the next parent just adds its mark instead of adding 
another child.


When a parent gets deleted from the master, its mark is removed from all 
the child records it was involved with and if it was the only mark the 
child gets deleted too. Or at least that is what I want to happen.


My question is:

In overview, how should I be doing this?

At the moment I'm trying to do it all via model methods calling various 
managers because it feels like the right place to do it.


I have tried to make a custom manager with use_for_related_fields = True 
but still get the same error.


Thanks for any help

Mike

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