#29222: Substr on NULL values returns incorrect results with pattern lookups.
-------------------------------------+-------------------------------------
Reporter: Mariusz Felisiak | Owner: Siddharth
| Panditrao
Type: Bug | Status: assigned
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Keywords: Oracle | Triage Stage: Accepted
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 Simon Charette):
I left a note to this effect [https://forum.djangoproject.com/t/fix-
oracle-bug-where-substr-null-with-pattern-lookups-matches-all-rows-
instead-of-none/43757 on the forum] but I'm afraid there isn't much we can
do here given `__startswith` and related lookups
[https://dryorm.xterm.info/ticket-29222 have historically accepted an
empty strings as their right-side-hand to match all rows].
Because `''` and `NULL` are the same thing on Oracle we have to choose; we
can't return all rows in the first case and no rows in the second like on
all other backends.
Given these lookups are meant to treat with text fields left-hand-sides in
which
[https://docs.djangoproject.com/en/6.0/ref/models/fields/#django.db.models.Field.null
we document that storing `NULL` is an anti-pattern]
> Avoid using `null` on string-based fields such as `CharField` and
`TextField`. The Django convention is to use an empty string, not `NULL`,
as the “no data” state for string-based fields.
and things have been working this way on Oracle since their inception I'd
be more inclined to wont-fix this ticket and accept it as a unfortunate
side effect of `interprets_empty_strings_as_nulls`.
--
Ticket URL: <https://code.djangoproject.com/ticket/29222#comment:7>
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