Hi David, *select_related* does a JOIN under the hood, and you can't do cross-database joins in the databases supported by Django. For prefetch_related, there is no way out of the box to perform a cross-database join in Python (which is what prefetch_related is doing) but perhaps there is some way to programatically make that happen. I haven't put any effort into exploring that idea.
Thanks, On Thu, May 21, 2015 at 3:42 PM, David <ld...@gmx.net> wrote: > Dear List, > > I came about conflicting information (to my mind) concerning the use of > select_related() and prefetch_related(). > My question is whether you can combine select_related() and > prefetch_related() with sharding techniques. If so, how are you doing it? > > Background: > I was watching various videos on Django under load and Django scaling, > generally there comes a point at which they point at database sharding. > Ash Christopher (https://www.youtube.com/watch?v=frlsGUHYu04) points out > that as you use multiple databases with your Application, > select_related() and prefetch_related() can no longer be used. In > Christophe Pettus' videos I have not found such a comment, in fact > select_related() and prefetch_related() seem to be habitually > recommended to speed database connections up. > > Thanks for your insights! > > David > -- 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 django-users+unsubscr...@googlegroups.com. To post to this group, send email to django-users@googlegroups.com. Visit this group at http://groups.google.com/group/django-users. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/CAJdxA4uqMB_-ovXehbiUnqaX6Co6LP7LPMKAf88fb-Zb6VW_%2BQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
