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On 02/19/2012 09:40 AM, Carl Meyer wrote: > On 02/18/2012 05:37 AM, Anssi Kääriäinen wrote: >> The second one is about .iterator() and .prefetch_related() >> interoperability. They are mutually exclusive (you need to fetch all >> the objects before you can do prefetch. However, .iterator() says do >> not fetch all the objects in one go...). There are basically three >> ways forward: raise an error, favor .iterator() (current behavior) or >> favor .prefetch_related(). > >> I think each one has some merit, and this is mostly bike-shedding. >> However, if you have good reasons for one of the options it would be >> good to hear them now. I would prefer either error or doing the >> prefetch even when iterator is used. As I don't recall ever actually >> using .iterator() in production I have no strong opinions. The ticket >> is #17668. > > I don't have a real strong opinion here either, but I think this rarity > of usage of .iterator() is an argument for favoring it. In my > experience, if you are bothering to use .iterator() it's because you > really know you need it; you are fetching a ton of items and loading > them all at once might run your server out of memory. Whereas the > consequence of ignoring prefetch_related is just extra SQL queries - > bad, but less likely to be catastrophic. > > That's all kind of handwavy, but in the absence of good hard reasons in > either direction, it's the best I've got :-) Actually, another reason to favor .iterator is that it's a terminal clause. So in any situation where iterator and prefetch_related are both used, iterator must have been used last. So favoring .iterator favors the most recent request, and in the hypothetical "you got the queryset from some other library" situation, favors the integrating developer's request. Carl -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk9BJ3gACgkQ8W4rlRKtE2djBwCeIQiWCfmazZ2clfkkrCcEqV6C g48An3q2IowQsgW5Q2zaYkDsNuY4BQRM =SeV6 -----END PGP SIGNATURE----- -- You received this message because you are subscribed to the Google Groups "Django developers" group. 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.
