#9554: select related - maximum depth
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Reporter: gert | Owner: nobody
Status: reopened | Milestone:
Component: Contrib apps | Version: 1.0
Resolution: | Keywords: select related
Stage: Unreviewed | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Comment (by gert):
ramiro: yes, I only picked it up in the admin contrib app. At that stage I
was unaware of the depth=X parameter. I think it adequately addresses the
issue for custom applications, also I don't think internally
select_related needs to drop the 5 down to 3.
BUT, for the admin application I think a tweak is required. Arguments for
explicitly lowering select_related for admin to say 3 :) are;
1) Whatever value you take must hit the sweat spot for 90% of situations
otherwise it will slow down rather than increase overall application
speed. I can not even think of an example where I want to go down 5
levels. (object.level1.level2.level3.level4.level5)
2) Remember that the effect on the database increases exponentially, e.g.
3 levels 2 references per object => 3^2^ = 9 DB tables
5 levels 2 references per object => 5^2^ = 25 DB tables
5 levels 3 references per object => 5^3^ = 125 DB tables
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Ticket URL: <http://code.djangoproject.com/ticket/9554#comment:5>
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