#16715: Wrong JOIN with nested null-able foreign keys
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Reporter: sebastian | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: SVN
(models, ORM) | Resolution:
Severity: Normal | Triage Stage: Accepted
Keywords: join, values, | Needs documentation: 0
nested, foreign key, null-able | Patch needs improvement: 0
Has patch: 1 | UI/UX: 0
Needs tests: 0 |
Easy pickings: 0 |
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Comment (by akaariai):
I think the approach in the sql/compiler.py is correct. However the
approach in sql/query.py is not correct in my opinion. What the NULLABLE
in alias_map tuples mean, is if the join is nullable considered separate
from the whole query. It is the responsibility of join promotion to do the
correct promotions in the join chain, taking in account the parent joins.
See attached patch for an approach doing this. I think my patch is
actually simplifying the code while at the same time correcting this
problem. However I am not yet at all certain it is actually correct. At
least it passes the test :)
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Ticket URL: <https://code.djangoproject.com/ticket/16715#comment:11>
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