Re: get_or_create gave IntegrityError: (1062, "Duplicate entry) error sometimes
Isn't it because MyISAM does not support transaction? BTW I am using django 1.3.1, mysql 5.5, innodb mysql> SELECT @@GLOBAL.tx_isolation, @@tx_isolation; +---+-+ | @@GLOBAL.tx_isolation | @@tx_isolation | +---+-+ | REPEATABLE-READ | REPEATABLE-READ | +---+-+ another question, does "read committed" affects performance? On 2012/10/16, at 0:35, Tom Evans wrote: > On Mon, Oct 15, 2012 at 3:28 PM, Karen Tracey wrote: >> On Mon, Oct 15, 2012 at 9:43 AM, Tom Evans wrote: >>> >>> On Mon, Oct 15, 2012 at 1:50 PM, Zheng Li wrote: get_or_create shouldn't give duplicate entry error anyone help. >>> >>> This is incorrect, and a common misconception: get_or_create() is not >>> atomic. If this happens, you will get duplicate key errors: >> >> >> No, get_or_create IS intended to be atomic. >> > > I can be intended to be whatever it wants, but since there is no > atomic database operation to get or create a tuple, there is no > guarantee of atomicity. > >>> >>> >>> Thread A calls get_or_create(a='a', b='b') >>> Thread B calls get_or_create(a='a', b='b') >>> Thread A get_or_create looks for entry in DB, not found >>> Thread B get_or_create looks for entry in DB, not found >>> Thread B creates entry in DB >>> Thread A get_or_create tries to create entry in DB >> >> >> Internally, get_or_create code in thread A will now attempt to GET the >> object created by thread B. It will not automatically reflect the error to >> the caller. See: >> >> https://github.com/django/django/blob/stable/1.4.x/django/db/models/query.py#L430 > > I regularly - once every few months - see get_or_create raise > IntegrityError due to duplicate key on MySQL 5.0/MyISAM/Django 1.3. So > whilst that is the intention of the code, it isn't what happens. I'm > happy to blame MySQL. > > Cheers > > Tom > > -- > You received this message because you are subscribed to the Google Groups > "Django users" group. > To post to this group, send email to django-users@googlegroups.com. > To unsubscribe from this group, send email to > django-users+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/django-users?hl=en. > -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: get_or_create gave IntegrityError: (1062, "Duplicate entry) error sometimes
On Mon, Oct 15, 2012 at 3:28 PM, Karen Tracey wrote: > On Mon, Oct 15, 2012 at 9:43 AM, Tom Evans wrote: >> >> On Mon, Oct 15, 2012 at 1:50 PM, Zheng Li wrote: >> > get_or_create shouldn't give duplicate entry error >> > anyone help. >> > >> >> This is incorrect, and a common misconception: get_or_create() is not >> atomic. If this happens, you will get duplicate key errors: > > > No, get_or_create IS intended to be atomic. > I can be intended to be whatever it wants, but since there is no atomic database operation to get or create a tuple, there is no guarantee of atomicity. >> >> >> Thread A calls get_or_create(a='a', b='b') >> Thread B calls get_or_create(a='a', b='b') >> Thread A get_or_create looks for entry in DB, not found >> Thread B get_or_create looks for entry in DB, not found >> Thread B creates entry in DB >> Thread A get_or_create tries to create entry in DB > > > Internally, get_or_create code in thread A will now attempt to GET the > object created by thread B. It will not automatically reflect the error to > the caller. See: > > https://github.com/django/django/blob/stable/1.4.x/django/db/models/query.py#L430 I regularly - once every few months - see get_or_create raise IntegrityError due to duplicate key on MySQL 5.0/MyISAM/Django 1.3. So whilst that is the intention of the code, it isn't what happens. I'm happy to blame MySQL. Cheers Tom -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: get_or_create gave IntegrityError: (1062, "Duplicate entry) error sometimes
On Mon, Oct 15, 2012 at 9:43 AM, Tom Evans wrote: > On Mon, Oct 15, 2012 at 1:50 PM, Zheng Li wrote: > > get_or_create shouldn't give duplicate entry error > > anyone help. > > > > This is incorrect, and a common misconception: get_or_create() is not > atomic. If this happens, you will get duplicate key errors: > No, get_or_create IS intended to be atomic. > > Thread A calls get_or_create(a='a', b='b') > Thread B calls get_or_create(a='a', b='b') > Thread A get_or_create looks for entry in DB, not found > Thread B get_or_create looks for entry in DB, not found > Thread B creates entry in DB > Thread A get_or_create tries to create entry in DB > Internally, get_or_create code in thread A will now attempt to GET the object created by thread B. It will not automatically reflect the error to the caller. See: https://github.com/django/django/blob/stable/1.4.x/django/db/models/query.py#L430 > > Where I say 'thread', you could also read 'process'. If you are > capable of serving multiple requests simultaneously, this can happen, > even if you aren't using threads. > > If this is a problem for you, use a transaction aware DB instead of > MySQL. It won't solve the issue, but at least you will be able to > unroll the transaction. > The issue with MySQL here is when you ARE using its transactional DB engine, InnoDB, AND using its (default) "repeatable read" transaction isolation level. In that case, the DB will refuse to return the object created by thread B to thread A if thread A has already "read" the non-existence of such a row. See: https://code.djangoproject.com/ticket/13906 This particular issue can be fixed by changing the transaction isolation level to "read committed". Although I have heard various people say this can cause "other problems" with MySQL apps, I've never seen a concrete example of one, so switching to "read committed" would be my preferred way to use get_or_created if I had to use MySQL/InnoDB. Karen -- http://tracey.org/kmt/ -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: get_or_create gave IntegrityError: (1062, "Duplicate entry) error sometimes
On Mon, Oct 15, 2012 at 1:50 PM, Zheng Li wrote: > get_or_create shouldn't give duplicate entry error > anyone help. > This is incorrect, and a common misconception: get_or_create() is not atomic. If this happens, you will get duplicate key errors: Thread A calls get_or_create(a='a', b='b') Thread B calls get_or_create(a='a', b='b') Thread A get_or_create looks for entry in DB, not found Thread B get_or_create looks for entry in DB, not found Thread B creates entry in DB Thread A get_or_create tries to create entry in DB Where I say 'thread', you could also read 'process'. If you are capable of serving multiple requests simultaneously, this can happen, even if you aren't using threads. If this is a problem for you, use a transaction aware DB instead of MySQL. It won't solve the issue, but at least you will be able to unroll the transaction. Cheers Tom -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: get_or_create gave IntegrityError: (1062, "Duplicate entry) error sometimes
On 15-10-12 14:50, Zheng Li wrote: get_or_create shouldn't give duplicate entry error Perhaps you have existing data that violates your unique-together constraint? Data that existed before that constraint was in place? Check it directly in your database by searching for that a=a, b=b entry. Reinout -- Reinout van Reeshttp://reinout.vanrees.org/ rein...@vanrees.org http://www.nelen-schuurmans.nl/ "If you're not sure what to do, make something. -- Paul Graham" -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: get_or_create gave IntegrityError: (1062, "Duplicate entry) error sometimes
get_or_create shouldn't give duplicate entry error
anyone help.
On 2012/10/13, at 11:06, Wei Wei wrote:
> I am new to Django. But does the error message literally mean you have
> duplicated records against your unique_together constriction?
>
> On Sat, Oct 13, 2012 at 9:47 AM, Zheng Li wrote:
> class AB(models.Model):
> a = models.ForeignKey(A)
> b = models.ForeignKey(B)
> c = models.IntegerField(default=0)
> d = models.FloatField(default=0)
> e = models.IntegerField(default=0)
> f = models.FloatField(default=0)
> class Meta:
> unique_together = (('a', 'b'),)
>
> I have a class like above.
> when I call get_or_create, sometimes IntegrityError: (1062, "Duplicate entry)
> error happens.
> a, _ = AB.objects.get_or_create(a=a, b=b)
>
> I really have googled and worked on it for a while, but still nothing.
> anyone can help?
> Thanks in advance.
>
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>
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Re: get_or_create gave IntegrityError: (1062, "Duplicate entry) error sometimes
I am new to Django. But does the error message literally mean you have
duplicated records against your unique_together constriction?
On Sat, Oct 13, 2012 at 9:47 AM, Zheng Li wrote:
> class AB(models.Model):
> a = models.ForeignKey(A)
> b = models.ForeignKey(B)
> c = models.IntegerField(default=0)
> d = models.FloatField(default=0)
> e = models.IntegerField(default=0)
> f = models.FloatField(default=0)
> class Meta:
> unique_together = (('a', 'b'),)
>
> I have a class like above.
> when I call get_or_create, sometimes IntegrityError: (1062, "Duplicate
> entry) error happens.
> a, _ = AB.objects.get_or_create(a=a, b=b)
>
> I really have googled and worked on it for a while, but still nothing.
> anyone can help?
> Thanks in advance.
>
> --
> You received this message because you are subscribed to the Google Groups
> "Django users" group.
> To post to this group, send email to django-users@googlegroups.com.
> To unsubscribe from this group, send email to
> django-users+unsubscr...@googlegroups.com.
> For more options, visit this group at
> http://groups.google.com/group/django-users?hl=en.
>
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get_or_create gave IntegrityError: (1062, "Duplicate entry) error sometimes
class AB(models.Model):
a = models.ForeignKey(A)
b = models.ForeignKey(B)
c = models.IntegerField(default=0)
d = models.FloatField(default=0)
e = models.IntegerField(default=0)
f = models.FloatField(default=0)
class Meta:
unique_together = (('a', 'b'),)
I have a class like above.
when I call get_or_create, sometimes IntegrityError: (1062, "Duplicate entry)
error happens.
a, _ = AB.objects.get_or_create(a=a, b=b)
I really have googled and worked on it for a while, but still nothing.
anyone can help?
Thanks in advance.
--
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