Re: [Django] #24009: get_or_create can raise an IntegrityError in race conditions

[Django]

#24009: get_or_create can raise an IntegrityError in race conditions
---+--
 Reporter:  lanzz  |Owner:  nobody
 Type:  Uncategorized  |   Status:  closed
Component:  Uncategorized  |  Version:  1.7
 Severity:  Normal |   Resolution:  needsinfo
 Keywords: | Triage Stage:  Unreviewed
Has patch:  0  |  Needs documentation:  0
  Needs tests:  0  |  Patch needs improvement:  0
Easy pickings:  0  |UI/UX:  0
---+--
Changes (by timgraham):

 * status:  new => closed
 * resolution:   => needsinfo


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Django 
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Re: [Django] #24009: get_or_create can raise an IntegrityError in race conditions

[Django]

#24009: get_or_create can raise an IntegrityError in race conditions
---+--
 Reporter:  lanzz  |Owner:  nobody
 Type:  Uncategorized  |   Status:  new
Component:  Uncategorized  |  Version:  1.7
 Severity:  Normal |   Resolution:
 Keywords: | Triage Stage:  Unreviewed
Has patch:  0  |  Needs documentation:  0
  Needs tests:  0  |  Patch needs improvement:  0
Easy pickings:  0  |UI/UX:  0
---+--

Comment (by timgraham):

 As far as I can tell, the `IntegrityError` you describe
 
[https://github.com/django/django/blob/6403e07c5093e0244497293f31f5f73cebe85b66/django/db/models/query.py#L468-L483
 should be caught by Django]. Did you run into this problem with Django
 1.7?

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The Web framework for perfectionists with deadlines.

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Re: [Django] #24009: get_or_create can raise an IntegrityError in race conditions

[Django]

#24009: get_or_create can raise an IntegrityError in race conditions
---+--
 Reporter:  lanzz  |Owner:  nobody
 Type:  Uncategorized  |   Status:  new
Component:  Uncategorized  |  Version:  1.7
 Severity:  Normal |   Resolution:
 Keywords: | Triage Stage:  Unreviewed
Has patch:  0  |  Needs documentation:  0
  Needs tests:  0  |  Patch needs improvement:  0
Easy pickings:  0  |UI/UX:  0
---+--

Comment (by lanzz):

 No, I'm using PostgreSQL, and wrapping each `get_or_create` in an
 individual transaction context will again make `get_or_create` worthless
 by requiring at least as much boilerplate around it as it would take to
 implement the get-or-create logic myself without using `get_or_create`.

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Re: [Django] #24009: get_or_create can raise an IntegrityError in race conditions

[Django]

#24009: get_or_create can raise an IntegrityError in race conditions
---+--
 Reporter:  lanzz  |Owner:  nobody
 Type:  Uncategorized  |   Status:  new
Component:  Uncategorized  |  Version:  1.7
 Severity:  Normal |   Resolution:
 Keywords: | Triage Stage:  Unreviewed
Has patch:  0  |  Needs documentation:  0
  Needs tests:  0  |  Patch needs improvement:  0
Easy pickings:  0  |UI/UX:  0
---+--
Changes (by timgraham):

 * needs_better_patch:   => 0
 * needs_tests:   => 0
 * needs_docs:   => 0


Comment:

 This may be a duplicate of #13906. Are you using MySQL with `REPEATABLE
 READ`?

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[Django] #24009: get_or_create can raise an IntegrityError in race conditions

[Django]

#24009: get_or_create can raise an IntegrityError in race conditions
---+
 Reporter:  lanzz  |  Owner:  nobody
 Type:  Uncategorized  | Status:  new
Component:  Uncategorized  |Version:  1.7
 Severity:  Normal |   Keywords:
 Triage Stage:  Unreviewed |  Has patch:  0
Easy pickings:  0  |  UI/UX:  0
---+
 `get_or_create` is described as being atomic in the documentation, but
 that is not the case. Since it first tries to retrieve an existing record
 and if that fails it tries to create a new one, another thread can create
 that record in the small interval between the two operations. This will
 not result in data corruption as the database will enforce its
 constraints, but it makes the whole convenience method not that
 convenient, if I also need to handle this in a `try` block around its
 invocation. If I _need_ to do `try: get_or_create() except IntegrityError:
 get()` anyway, it makes no sense to use `get_or_create` in the first
 place, that logic would work if I just try to create the entity and only
 retrieve it if the create raises an `IntegrityError`.

 When I call `get_or_create` I expect it to return the existing record, or
 to create a new record if one does not exist yet. Getting an
 `IntegrityError` there is like saying "there's no existing record, but I
 cannot create a new one because one already exists".

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Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

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