Re: Generating a unique 10 digit ID for each model instance

[Mark Phillips]

I thought python's uuid.uuid4 guaranteed a unique value. Am I missing
something?

Mark

On Sun, Oct 22, 2017 at 3:58 PM, James Schneider 
wrote:

>
>
> On Oct 22, 2017 12:29 PM, "Andréas Kühne" 
> wrote:
>
> Hi,
>
> I think you are correct with your pseudocode - you can do a
> Model.objects.filter(unique_code==random_code).count() - and then loop on
> that. It should work.
>
>
> I wouldn't do this, it can lead to a race condition where you can possibly
> end up with duplicate ID's if two objects are being inserted at the same
> time.
>
> Ensure that you have a unique index on the ID column, then just create
> your ID and try to insert it into the DB. Let the DB determine whether or
> not it is unique, it is much better at this than any Python code you can
> write. If it falils, catch the insertion error, change the ID, and try
> again.
>
> Even if you did do this, you should use .exists() rather than .count().
>
> Either way, your code should be prepared to deal with the potential for
> duplicate ID's being inserted in to the database.
>
> -James
>
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Re: Generating a unique 10 digit ID for each model instance

[James Schneider]

On Oct 22, 2017 12:29 PM, "Andréas Kühne" 
wrote:

Hi,

I think you are correct with your pseudocode - you can do a
Model.objects.filter(unique_code==random_code).count() - and then loop on
that. It should work.


I wouldn't do this, it can lead to a race condition where you can possibly
end up with duplicate ID's if two objects are being inserted at the same
time.

Ensure that you have a unique index on the ID column, then just create your
ID and try to insert it into the DB. Let the DB determine whether or not it
is unique, it is much better at this than any Python code you can write. If
it falils, catch the insertion error, change the ID, and try again.

Even if you did do this, you should use .exists() rather than .count().

Either way, your code should be prepared to deal with the potential for
duplicate ID's being inserted in to the database.

-James

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Re: Generating a unique 10 digit ID for each model instance

[Andréas Kühne]

Hi,

I think you are correct with your pseudocode - you can do a
Model.objects.filter(unique_code==random_code).count() - and then loop on
that. It should work.

The reason why I thought you should use the signals is because thats how I
have done the same things in the past. However, you can just overload the
save method and then do it there (if there is no PK).

Regards,

Andréas

2017-10-22 20:53 GMT+02:00 Jack Zhang :

> Hi Andréas,
>
> Yes, by globally unique I mean a unique 10-digit ID is assigned to every
> model instance of 'Dogs' within my application.  This ID will be shown
> publicly on the website to allow easy search access to a specific model
> instance.
>
> I think you are right about creating a new field to hold the unique ID,
> instead of using the primary key.  Generating the ID is not too difficult,
> but how can I ensure that I won't generate a duplicate ID?  From briefly
> thinking about it, this is what I got...
>
> When a new instance is created, generate *new ID*
> For every *existing ID* in the database:
>  If *new ID* == *existing ID* in the database:
>   Generate *new ID* and re-run the for loop
> If *new ID* does not match any *existing ID * in the database, proceed
> with continuing the model instance.
>
> Also I read up on Signals, but is it necessary?
>
>
> On Sunday, October 22, 2017 at 12:30:02 PM UTC-4, Andréas Kühne wrote:
>>
>> Hi,
>>
>> When you say "globally unique" - I am supposing you mean within your
>> application?
>>
>> What you need to do is set a field to be the primary key, see :
>> https://docs.djangoproject.com/en/1.11/topics/db/models/#a
>> utomatic-primary-key-fields
>>
>> However - it would be simpler to use the standard primary key auto id
>> field, and then add another field to hold your unique ID in it. This could
>> then be created on the pre_save signal and you could write something that
>> randomly generates the unique ID field. See https://docs.djangoproject
>> .com/en/1.11/topics/signals/
>>
>> Best regards,
>>
>> Andréas
>>
>> 2017-10-22 17:52 GMT+02:00 Jack Zhang :
>>
>>> Let's say I have a model called 'Dogs'.  Users can create instances of
>>> Dogs.  For every Dogs instance that is created, I want to assign a globally
>>> unique ID to it.  The ID will be 3 capitalized letters followed by 7
>>> numbers.  E.g. ABC1234567, POZ2930193
>>>
>>> What is the easiest way to go about doing this?  I looked into UUID but
>>> it generates a longer string.  Keep in mind that the ID must be globally
>>> unique - so after one has been created, it should not be created again.
>>>
>>> Thanks.
>>>
>>> --
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>>
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Re: Generating a unique 10 digit ID for each model instance

[Jack Zhang]

I need this 10-digit unique ID for every model instance so users can easily 
search up a specific model instance.  It will be publicly displayed on the 
website, unlike a primary key which is usually hidden

On Sunday, October 22, 2017 at 1:31:23 PM UTC-4, Avraham Serour wrote:
>
> The database usually handles this and you don't need to worry, there are 
> many corner cases and DB systems are able to handle them
>
> But they won't look like whatever format you would like, usually it is 
> just a number
>
> Why do you need the IDs to look like that?
>
> On Oct 22, 2017 6:53 PM, "Jack Zhang"  
> wrote:
>
>> Let's say I have a model called 'Dogs'.  Users can create instances of 
>> Dogs.  For every Dogs instance that is created, I want to assign a globally 
>> unique ID to it.  The ID will be 3 capitalized letters followed by 7 
>> numbers.  E.g. ABC1234567, POZ2930193
>>
>> What is the easiest way to go about doing this?  I looked into UUID but 
>> it generates a longer string.  Keep in mind that the ID must be globally 
>> unique - so after one has been created, it should not be created again.
>>
>> Thanks.
>>
>> -- 
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>> "Django users" group.
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>> https://groups.google.com/d/msgid/django-users/0cd8e33c-8c92-471c-9c36-ac82749750b4%40googlegroups.com
>>  
>> 
>> .
>> For more options, visit https://groups.google.com/d/optout.
>>
>

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Re: Generating a unique 10 digit ID for each model instance

[Jack Zhang]

Hi Andréas,

Yes, by globally unique I mean a unique 10-digit ID is assigned to every 
model instance of 'Dogs' within my application.  This ID will be shown 
publicly on the website to allow easy search access to a specific model 
instance.

I think you are right about creating a new field to hold the unique ID, 
instead of using the primary key.  Generating the ID is not too difficult, 
but how can I ensure that I won't generate a duplicate ID?  From briefly 
thinking about it, this is what I got...

When a new instance is created, generate *new ID*
For every *existing ID* in the database:
 If *new ID* == *existing ID* in the database:
  Generate *new ID* and re-run the for loop
If *new ID* does not match any *existing ID * in the database, proceed with 
continuing the model instance.

Also I read up on Signals, but is it necessary?


On Sunday, October 22, 2017 at 12:30:02 PM UTC-4, Andréas Kühne wrote:
>
> Hi,
>
> When you say "globally unique" - I am supposing you mean within your 
> application?
>
> What you need to do is set a field to be the primary key, see : 
> https://docs.djangoproject.com/en/1.11/topics/db/models/#automatic-primary-key-fields
>
> However - it would be simpler to use the standard primary key auto id 
> field, and then add another field to hold your unique ID in it. This could 
> then be created on the pre_save signal and you could write something that 
> randomly generates the unique ID field. See 
> https://docs.djangoproject.com/en/1.11/topics/signals/
>
> Best regards,
>
> Andréas
>
> 2017-10-22 17:52 GMT+02:00 Jack Zhang :
>
>> Let's say I have a model called 'Dogs'.  Users can create instances of 
>> Dogs.  For every Dogs instance that is created, I want to assign a globally 
>> unique ID to it.  The ID will be 3 capitalized letters followed by 7 
>> numbers.  E.g. ABC1234567, POZ2930193
>>
>> What is the easiest way to go about doing this?  I looked into UUID but 
>> it generates a longer string.  Keep in mind that the ID must be globally 
>> unique - so after one has been created, it should not be created again.
>>
>> Thanks.
>>
>> -- 
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>> "Django users" group.
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>> email to django-users...@googlegroups.com .
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>> .
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>> https://groups.google.com/d/msgid/django-users/0cd8e33c-8c92-471c-9c36-ac82749750b4%40googlegroups.com
>>  
>> 
>> .
>> For more options, visit https://groups.google.com/d/optout.
>>
>
>

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Re: Generating a unique 10 digit ID for each model instance

[Avraham Serour]

The database usually handles this and you don't need to worry, there are
many corner cases and DB systems are able to handle them

But they won't look like whatever format you would like, usually it is just
a number

Why do you need the IDs to look like that?

On Oct 22, 2017 6:53 PM, "Jack Zhang"  wrote:

> Let's say I have a model called 'Dogs'.  Users can create instances of
> Dogs.  For every Dogs instance that is created, I want to assign a globally
> unique ID to it.  The ID will be 3 capitalized letters followed by 7
> numbers.  E.g. ABC1234567, POZ2930193
>
> What is the easiest way to go about doing this?  I looked into UUID but it
> generates a longer string.  Keep in mind that the ID must be globally
> unique - so after one has been created, it should not be created again.
>
> Thanks.
>
> --
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Re: Live Django application on heroku.

[Harish Soni]

I'm getting error status 404 and after open url its showing requested url
not found on this server

On Oct 22, 2017 7:59 PM, "Chinonso Okoroafor" 
wrote:

> Go to https://devcenter.heroku.com/articles/getting-started-
> with-python#introduction you will find your answer there
>
> On Sunday, October 22, 2017 at 1:15:51 PM UTC+1, Harish Soni wrote:
>>
>> Hi All
>>
>> I'm having an assignment to make this application live on heroku but I am
>> not aware about structure and changes what should I have to make it into
>> this project so I can easily make this project to live.. I got so many
>> answers but not understood so if any help from your side would be
>> appreciable.
>>
>> Thanks in Advance
>>
>> Harish Soni Swarnkar
>>
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Re: Generating a unique 10 digit ID for each model instance

[Andréas Kühne]

Hi,

When you say "globally unique" - I am supposing you mean within your
application?

What you need to do is set a field to be the primary key, see :
https://docs.djangoproject.com/en/1.11/topics/db/models/#automatic-primary-key-fields

However - it would be simpler to use the standard primary key auto id
field, and then add another field to hold your unique ID in it. This could
then be created on the pre_save signal and you could write something that
randomly generates the unique ID field. See
https://docs.djangoproject.com/en/1.11/topics/signals/

Best regards,

Andréas

2017-10-22 17:52 GMT+02:00 Jack Zhang :

> Let's say I have a model called 'Dogs'.  Users can create instances of
> Dogs.  For every Dogs instance that is created, I want to assign a globally
> unique ID to it.  The ID will be 3 capitalized letters followed by 7
> numbers.  E.g. ABC1234567, POZ2930193
>
> What is the easiest way to go about doing this?  I looked into UUID but it
> generates a longer string.  Keep in mind that the ID must be globally
> unique - so after one has been created, it should not be created again.
>
> Thanks.
>
> --
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> msgid/django-users/0cd8e33c-8c92-471c-9c36-ac82749750b4%40googlegroups.com
> 
> .
> For more options, visit https://groups.google.com/d/optout.
>

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Generating a unique 10 digit ID for each model instance

[Jack Zhang]

Let's say I have a model called 'Dogs'.  Users can create instances of 
Dogs.  For every Dogs instance that is created, I want to assign a globally 
unique ID to it.  The ID will be 3 capitalized letters followed by 7 
numbers.  E.g. ABC1234567, POZ2930193

What is the easiest way to go about doing this?  I looked into UUID but it 
generates a longer string.  Keep in mind that the ID must be globally 
unique - so after one has been created, it should not be created again.

Thanks.

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Re: Live Django application on heroku.

[Chinonso Okoroafor]

Go 
to 
https://devcenter.heroku.com/articles/getting-started-with-python#introduction 
you will find your answer there

On Sunday, October 22, 2017 at 1:15:51 PM UTC+1, Harish Soni wrote:
>
> Hi All 
>
> I'm having an assignment to make this application live on heroku but I am 
> not aware about structure and changes what should I have to make it into 
> this project so I can easily make this project to live.. I got so many 
> answers but not understood so if any help from your side would be 
> appreciable.
>
> Thanks in Advance
>
> Harish Soni Swarnkar
>

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Live Django application on heroku.

[Harish Soni]

Hi All 

I'm having an assignment to make this application live on heroku but I am 
not aware about structure and changes what should I have to make it into 
this project so I can easily make this project to live.. I got so many 
answers but not understood so if any help from your side would be 
appreciable.

Thanks in Advance

Harish Soni Swarnkar

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Re: dynamic choices based on another field input.

[Derek]

See:

http://django-autocomplete-light.readthedocs.io/en/master/tutorial.html#filtering-results-based-on-the-value-of-other-fields-in-the-form


On Friday, 20 October 2017 13:04:41 UTC+2, rajeev yadla wrote:
>
> hi have a form which have two fields. one field has a foreignkey from 
> model A(in image) base field. and another field is a drop down box where 
> the choices should be dynamic based on first field selection. the choices 
> should all the values of field Os from second model B associated with the 
> Base key value i have given in first field. 
> example from image. 
> field 1= 10
> field 2= (A,C) as these two values are associted with 10 in model B.
>
>
> 
>
> can someone help me here.
>

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Re: Django 1.11 and PostgreSQL 10 compatibility

[Edandweb]

Thanks

On Thursday, 19 October 2017 12:27:50 UTC+3, Edandweb wrote:
>
> Hi,
>
> I am developing a new application in Python and Django, for the database 
> we want to use the last version of PostgreSQL v10.
> The django Documentation says in 
> https://docs.djangoproject.com/en/1.11/ref/databases/#postgresql-notes:
>
>
>
> *Django supports PostgreSQL 9.3 and higher. psycopg2 
>  2.5.4 or higher is required, though the latest 
> release is recommended.*I am not sure to understand, it's just 9.3 and 
> higher like 9.3.1 or 9.3.2 or 9.3.4 ... or can we use 9.4 and 9.5 ... ?
>
> Thanks 
>
>

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