#9166: stupid SQL
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Reporter: [EMAIL PROTECTED] | Owner:
nobody
Status: closed | Milestone: post-1.0
Component: Database layer (models, ORM) | Version: 1.0
Resolution: wontfix | Keywords: STUPID SQL
Stage: Unreviewed | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Changes (by mtredinnick):
* status: new => closed
* resolution: => wontfix
Comment:
This rapidly gets very, very difficult once you have more than one related
model, because adding all the fields to select leads to selecting N * M
rows, if there are N rows in the first related table and M in the second
(instead of N + M + 1 rows, which is the ideal). The `select_related()`
processing is already fairly complex, so this isn't a trivial change. When
somebody writes a solid patch to improve it, we'll certainly accept it.
There's already a ticket open to add similar "follow reverse relations"
for `select_related()` and #7270 handles the special case of reverse
!OneToOneFields (which is the one case where multiple rows won't be
returned).
It isn't stupid SQL, it's a conscious decision to avoid a very bad
performance overhead. The same effect can be achieved in almost all cases
(including the above one) by turning the second queryset around to be a
query on the Translation table using the book ids that you already know,
so it's two queries not 101.
"Wontfixing" this ticket, since the behaviour is documented and
intentional. If somebody writes a patch to make things better, it can be
attached to a ticket at that time.
--
Ticket URL: <http://code.djangoproject.com/ticket/9166#comment:2>
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