#24082: Unique=True on TextField or CharField should not create an index
-------------------------------------+-------------------------------------
Reporter: djbug | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.7
(models, ORM) |
Severity: Normal | Resolution:
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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Comment (by djbug):
> the issue here really is whether `unique=True` implies `db_index=True`.
This holds for most field types, so I think most people would expect it to
hold for text fields as well.
Could you explain why should `unique=True` imply creation of an index
explicitly ? AFAIK, this would duplicate the index in PostgreSQL (& a few
other databases according to the old bug reports mentioned above). If we
remove this explicit index, there's no drop in performance because
internally the db maintains an index for a unique constraint.
> You should get the behavior you expect, probably, with `unique=True,
db_index=False`. If this indeed gives you what you want, I'd resolve this
ticket by adding an admonition about this in the `TextField`
documentation.
I've tried your suggestion. For a `TextFIeld`, the following two generate
the same constraint & index:
{{{
TextField( unique=True, db_index=False)
}}}
and
{{{
TextField( unique=True)
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/24082#comment:5>
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