Create Django model or update if exists

Question

I want to create a model object  like Person  if person s id doesn t not exist  or I will get that person object    The code to create a new person as following   class Person models Model       identifier   models CharField max length   10      name   models CharField max length   20      objects   PersonManager    class PersonManager models Manager       def create person self  identifier           person   self create identifier   identifier          return person   But I don t know where to check and get the existing person object

User · Answer

For only a small amount of objects the update or create works well  but if you re doing over a large collection it won t scale well  update or create always first runs a SELECT and thereafter an UPDATE   for the bar in bars      updated rows   SomeModel objects filter bar the bar  update foo 100          if not updated rows                if not exists  create new             SomeModel objects create bar the bar  foo 100    This will at best only run the first update-query  and only if it matched zero rows run another INSERT-query  Which will greatly increase your performance if you expect most of the rows to actually be existing   It all comes down to your use case though  If you are expecting mostly inserts then perhaps the bulk create   command could be an option

User · Answer

You can also use update or create just like get or create and here is the pattern I follow for update or create assuming a model Person with id  key   name  age  is manager as attributes - update values     quot is manager quot   False  new values     quot name quot    quot Bob quot    quot age quot   25   quot is manager quot  True   obj  created   Person objects update or create identifier  id                                                  defaults update values  if created      obj update   new values

User · Answer

Thought I d add an answer since your question title looks like it is asking how to create or update  rather than get or create as described in the question body  If you did want to create or update an object  the  save   method already has this behaviour by default  from the docs   Django abstracts the need to use INSERT or UPDATE SQL statements  Specifically  when you call save    Django follows this algorithm  If the object   s primary key attribute is set to a value that evaluates to True  i e   a value other than None or the empty string   Django executes an UPDATE  If the object   s primary key attribute is not set or if the UPDATE didn   t update anything  Django executes an INSERT   It s worth noting that when they say  if the UPDATE didn t update anything  they are essentially referring to the case where the id you gave the object doesn t already exist in the database

User · Answer

This should be the answer you are looking for EmployeeInfo objects update or create       id or any primary key value to search for     identifier your id        if found update with the following or save create if not found     defaults   name   your name

User · Answer

It s unclear whether your question is asking for the get or create method  available from at least Django 1 3  or the update or create method  new in Django 1 7    It depends on how you want to update the user object   Sample use is as follows     In both cases  the call will get a person object with matching   identifier or create one if none exists  if a person is created    it will be created with name equal to the value in  name      In this case  if the Person already exists  its existing name is preserved person  created   Person objects get or create          identifier identifier  defaults   name   name       In this case  if the Person already exists  its name is updated person  created   Person objects update or create          identifier identifier  defaults   name   name

User · Answer

If one of the input when you create is a primary key  this will be enough   Person objects get or create id 1    It will automatically update if exist since two data with the same primary key is not allowed

User · Answer

Django has support for this  check get or create  person  created   Person objects get or create name  abc   if created        A new person object created else        person object already exists

User · Answer

If you re looking for  update if exists else create  use case  please refer to  Zags excellent answer    Django already has a get or create  https   docs djangoproject com en dev ref models querysets  get-or-create  For you it could be    id    some identifier  person  created   Person objects get or create identifier id   if created       means you have created a new person else       person just refers to the existing one

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