#31940: Order of WHERE clauses do not match the order of the arguments to
.filter().
-------------------------------------+-------------------------------------
Reporter: Tommy Li | Owner: nobody
Type: | Status: closed
Cleanup/optimization |
Component: Database layer | Version: 3.0
(models, ORM) |
Severity: Normal | Resolution: wontfix
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Changes (by felixxm):
* keywords: orm =>
* status: new => closed
* type: Bug => Cleanup/optimization
* resolution: => wontfix
Comment:
Thanks for this ticket.
> After some experimentation, it looks like the WHERE clauses are ordered
alphabetically by column name. Is that explicitly intended, or is it just
a side effect of some implementation detail?
`QuerySet.filter()` uses `Q()` objects. We added sorting to `kwargs` to
make `Q.deconstruct()` deterministic on Python 3.5, see #29125. Django
3.0+ supports only Python 3.6+, so we could theoretically revert this fix,
but this will generate migrations for existing project. I think it isn't
worth.
> I would expect the order of the clauses in the WHERE statement to match
the order of arguments passed to the filter statement. In my case, b_field
has a much higher cardinality than a_field and I want the query to use an
index I have on (b_field, a_field)
Clauses ordering should not affect indexes, as far as I'm aware databases
will use a `(b, a)`-index in both cases `b=1 AND a=2` and `a=2 AND b=1`.
--
Ticket URL: <https://code.djangoproject.com/ticket/31940#comment:2>
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