Well, you should've said that in the first post. First I would try with a saner DB (Postgres)
Also I don't think 300 ms is particularly bad, but in that case start looking into caching alternatives (e.g. memcached) or a search index (e.g. ElasticSearch) On Sat, Feb 3, 2018 at 3:14 AM, Web Architect <[email protected]> wrote: > Hi Furbee, > > Thanks for your response. > > With my experience I have always noticed that a query within query kills > the mysql and Mysqld CPU usage hits the ceiling. I would still check your > alternate. > > I have mentioned the size of A and B in response to Vijay's reply. > > On Saturday, February 3, 2018 at 1:06:48 AM UTC+5:30, Furbee wrote: >> >> There are a couple options you could try to see which is the best fit for >> your data. With DEBUG=True in settings.py you can check the actual queries >> and process time. It depends on the sizes of A and B. Another query you can >> run is: >> >> A.objects.exclude(id__in=B.objects.all().values_list('a_id', flat=True)) >> >> When I tried, it seemed to be about the same speed with my test data as >> the one you had A.objects.filter(bs__isnull=True). >> >> To see what queries are generated and the query time with DEBUG=True: >> Open your Django Python Shell >> >>> A.objects.exclude(id__in=B.objects.all().values_list('a_id', >> flat=True)) >> >>> A.objects.filter(bs__isnull=True) >> >>> from django.db import connection >> >>> for q in connection.queries: >> >>> print("{0}: {1}".format(q['sql'], q['time'])) >> >> This will show you both queries generated and how long it took to get a >> response from your DB. >> >> You can also write raw SQL, if you can make one more efficiently. >> >> Furbee >> >> On Fri, Feb 2, 2018 at 10:56 AM, Vijay Khemlani <[email protected]> >> wrote: >> >>> "with large of records in A and B, the above takes lot of time" >>> >>> How long? At first glance it doesn't look like a complex query or >>> something particularly inefficient for a DB. >>> >>> On Fri, Feb 2, 2018 at 11:31 AM, Andy <[email protected]> wrote: >>> >>>> not that i know of >>>> >>>> >>>> Am Freitag, 2. Februar 2018 15:28:26 UTC+1 schrieb Web Architect: >>>>> >>>>> Hi Andy, >>>>> >>>>> Thanks for your response. I was pondering on option a before posting >>>>> this query thinking there could be better ways in django/SQL to handle >>>>> this. But now I would probably go with a. >>>>> >>>>> Thanks. >>>>> >>>>> On Friday, February 2, 2018 at 7:50:53 PM UTC+5:30, Andy wrote: >>>>>> >>>>>> a) Maybe its an option to put the foreign key to the other model? >>>>>> This way you dont need to make a join to find out if there is a relation. >>>>>> >>>>>> b) Save the existing ralation status to model A >>>>>> >>>>>> c) cache the A.objects.filter(bs__isnull=False) query >>>>>> >>>>>> But apart from that i fear you cannot do much more, since this is >>>>>> just a DB and not a Django ORM question. >>>>>> >>>>>> >>>>>> Am Freitag, 2. Februar 2018 14:47:45 UTC+1 schrieb Web Architect: >>>>>>> >>>>>>> Hi, >>>>>>> >>>>>>> I am trying to optimise Django queries on my ecommerce website. One >>>>>>> of the fundamental query is where I have no clue how to make efficient. >>>>>>> It >>>>>>> could be trivial and probably been known long time back. But I am new to >>>>>>> Django and would appreciate any help. This is primarily for one to many >>>>>>> or >>>>>>> many to many relations. >>>>>>> >>>>>>> Following is an example scenario: >>>>>>> (Please pardon my syntax as I want to put across the concept and not >>>>>>> the exact django code unless it's really needed): >>>>>>> >>>>>>> Model A: >>>>>>> >>>>>>> class A(models.Model): >>>>>>> # Fields of model A >>>>>>> >>>>>>> Model B (which is related to A with foreign key): >>>>>>> >>>>>>> class B(models.Model): >>>>>>> a = models.ForeignKey('A', related_name='bs') >>>>>>> >>>>>>> Now I would like to find out all As for which there is atleast one >>>>>>> b. The only way I know is as follows: >>>>>>> >>>>>>> A.objects.filter(bs__isnull=False) >>>>>>> >>>>>>> But the above isn't an optimal way as with large of records in A and >>>>>>> B, the above takes lot of time. It gets more inefficient if it's a many >>>>>>> to >>>>>>> many relationship. >>>>>>> >>>>>>> Could anyone please let me know the most efficient way to use django >>>>>>> queryset for the above scenario? >>>>>>> >>>>>>> Thanks. >>>>>>> >>>>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "Django users" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To post to this group, send email to [email protected]. >>>> Visit this group at https://groups.google.com/group/django-users. >>>> To view this discussion on the web visit https://groups.google.com/d/ms >>>> gid/django-users/73ed5ff7-d4db-4057-a812-01c82bf08cf3%40goog >>>> legroups.com >>>> <https://groups.google.com/d/msgid/django-users/73ed5ff7-d4db-4057-a812-01c82bf08cf3%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Django users" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To post to this group, send email to [email protected]. >>> Visit this group at https://groups.google.com/group/django-users. >>> To view this discussion on the web visit https://groups.google.com/d/ms >>> gid/django-users/CALn3ei1Q2p31NrcdYC-2EPfH78kBxCXZPZKW1e6k%2 >>> BqCTuUgYDw%40mail.gmail.com >>> <https://groups.google.com/d/msgid/django-users/CALn3ei1Q2p31NrcdYC-2EPfH78kBxCXZPZKW1e6k%2BqCTuUgYDw%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- > You received this message because you are subscribed to the Google Groups > "Django users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/django-users. > To view this discussion on the web visit https://groups.google.com/d/ > msgid/django-users/07ef18a2-522f-4ae2-b9a6-1dc1293a413d%40googlegroups.com > <https://groups.google.com/d/msgid/django-users/07ef18a2-522f-4ae2-b9a6-1dc1293a413d%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/django-users. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/CALn3ei0eF9yk0ehtibK0J%3DBLB4ozcSpvsDqq9X-t%3Dh4imqinRQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
