суббота, 17 марта 2012 г. 0:15:39 UTC+6 пользователь dstufft написал: > > On Friday, March 16, 2012 at 2:08 PM, Luke Sneeringer wrote: > > Here's my hit list of perceived benefits: > 1. It regains the efficiency of a single table (which is minor, to be > sure, but since Jacob already brought it up...) > > This issue isn't as minor as one might think I don't believe. I've > recently started using the fetch_related thing (which would be the only way > to prevent N queries when trying to select a bunch of users + their > profiles) and on a table with 20k entries (this isn't User related) where > the entries are fairly large the processing time to fetch them all was very > significant. This effect would increase with Tom's per app profile issue. >
If the Profile model has OneToOne relation to User (as suggested in django docs [1]) then prefetch_related is not necessary, select_related can be used to get all records using single JOIN query. And storing more data in a single table could reduce performance, not increase it, because this data will be fetched by default even if it is not necessary (+ database will have larger rows to search in) - this effect would increase if there are several user profiles :) Storing all data in a single table is database denormalization: sometimes it can be benifical but should not be default in my opinion. [1] https://docs.djangoproject.com/en/1.3/topics/auth/#storing-additional-information-about-users -- You received this message because you are subscribed to the Google Groups "Django developers" group. To view this discussion on the web visit https://groups.google.com/d/msg/django-developers/-/1Bt6KG98h8wJ. To post to this group, send email to django-developers@googlegroups.com. To unsubscribe from this group, send email to django-developers+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-developers?hl=en.
