Re: Querysets returns wrong result when using threading.
Fantastic, thank you :) On Jan 16, 9:02 pm, Tomasz Zieliński wrote: > On 16 Sty, 06:15, Kieran Brownlees wrote: > > > Firstly thank you, secondly, how to get around it? I assume I need to > > force a commit for the transaction my thread is using, but querysets > > don't appear to have a documented method to do that. > > Yes, there is separate module for that: > > from django.db import transaction > transaction.commit() > > -- > Tomasz Zielinskihttp://pyconsultant.eu -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-us...@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: Querysets returns wrong result when using threading.
Firstly thank you, secondly, how to get around it? I assume I need to force a commit for the transaction my thread is using, but querysets don't appear to have a documented method to do that. Thank you On Jan 16, 1:52 am, Tomasz Zieliński wrote: > On 15 Sty, 05:33, James Bennett wrote: > > > On Thu, Jan 14, 2010 at 10:26 PM, Kieran Brownlees > > wrote: > > > Basic example of format: > > > Main Thread: print objects.all() > > > Spawned Thread: print objects.all() -- same as main thread > > > Main Thread: objects.create(newObj) > > > Main Thread: print.objects.all() -- correct queryset, original + new > > > Spawned Thread: print objects.all() -- only contains the original > > > objects, not the new one? > > > This would be the expected result with the default transaction > > isolation of most databases, and has nothing to do with threading. > > To be more explicit - Python DB API spec states that connection > should, by default, have autocommit turned on - which means that there > is always an ongoing transaction at DB level. > > Now, for MySQL backend, which I'm most familiar with, > default isolation level is REPEATABLE READ, which means > that first access to given table freezes its state for the duration > of current transaction. > > And because Django default behaviour is @autocommit, > i.e. it doesn't issue any COMMIT/ROLLBACK statements > for fetches, only for writes, all subsequent queries results > in the same queryset (in terms of elements, not object id). > > -- > Tomasz Zielinskihttp://pyconsultant.eu -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-us...@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: Querysets returns wrong result when using threading.
On 15 Sty, 05:33, James Bennett wrote: > On Thu, Jan 14, 2010 at 10:26 PM, Kieran Brownlees > wrote: > > Basic example of format: > > Main Thread: print objects.all() > > Spawned Thread: print objects.all() -- same as main thread > > Main Thread: objects.create(newObj) > > Main Thread: print.objects.all() -- correct queryset, original + new > > Spawned Thread: print objects.all() -- only contains the original > > objects, not the new one? > > This would be the expected result with the default transaction > isolation of most databases, and has nothing to do with threading. > To be more explicit - Python DB API spec states that connection should, by default, have autocommit turned on - which means that there is always an ongoing transaction at DB level. Now, for MySQL backend, which I'm most familiar with, default isolation level is REPEATABLE READ, which means that first access to given table freezes its state for the duration of current transaction. And because Django default behaviour is @autocommit, i.e. it doesn't issue any COMMIT/ROLLBACK statements for fetches, only for writes, all subsequent queries results in the same queryset (in terms of elements, not object id). -- Tomasz Zielinski http://pyconsultant.eu -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-us...@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: Querysets returns wrong result when using threading.
On Thu, Jan 14, 2010 at 10:26 PM, Kieran Brownlees wrote: > Basic example of format: > Main Thread: print objects.all() > Spawned Thread: print objects.all() -- same as main thread > Main Thread: objects.create(newObj) > Main Thread: print.objects.all() -- correct queryset, original + new > Spawned Thread: print objects.all() -- only contains the original > objects, not the new one? This would be the expected result with the default transaction isolation of most databases, and has nothing to do with threading. -- "Bureaucrat Conrad, you are technically correct -- the best kind of correct." -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-us...@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.
Querysets returns wrong result when using threading.
Hello All, Using Django 1.1.1. Today I found some very strange behaviour when trying to use theading, from what I understand it is different from the notes on trac of querysets not being thread safe. Basic issue trying to execute queries while in a thread always returns an original query. Probably best explained with an example (bit rushed by time at the end of the day! Sorry for the non generic example.): http://pastebin.com/m63211552 Basic example of format: Main Thread: print objects.all() Spawned Thread: print objects.all() -- same as main thread Main Thread: objects.create(newObj) Main Thread: print.objects.all() -- correct queryset, original + new Spawned Thread: print objects.all() -- only contains the original objects, not the new one? Full output (also shown in pastebin) test: [] In thread threadTest: [] Thread waiting Creating new db entry test: [, ] threadTest: [] Thank you, Kieran -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-us...@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.
