#36886: URLField max_length cannot take advantage of
supports_unlimited_charfield
in DB backend
-------------------------------------+-------------------------------------
Reporter: Joel D | Owner: Joel D Sleppy
Sleppy |
Type: | Status: assigned
Uncategorized |
Component: Database | Version: 6.0
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
When using a DB backend that `supports_unlimited_charfield` (postgres,
sqlite), a `CharField` can omit `max_length` and allow arbitrarily long
values in the database. However `URLField`, which inherits from
`CharField`, forces the developer to pick a maximum length. For example,
this model class:
{{{#!python
class Thing(models.Model):
chars = models.CharField()
url = models.URLField()
}}}
Creates this table in postgres:
{{{
Table "public.app_thing"
Column | Type | Collation | Nullable |
Default
--------+------------------------+-----------+----------+----------------------------------
id | bigint | | not null | generated by
default as identity
chars | character varying | | not null |
url | character varying(200) | | not null |
}}}
And trying to set `url = models.URLField(max_length=None)` does not get
recognized as a change by `makemigrations`.
URLs can get quite long and it's an inconvenience to pick a maximum length
(and to defensively code against the possibility of it being violated).
I'd like to work on this improvement myself if there's any appetite for
it.
Possible changes:
- For backwards compatibility, continue to default `max_length` to `200`
but allow specifying `None` to have an unbounded field.
- Break backwards compatibility, changing behavior to match that of
`CharField`.
--
Ticket URL: <https://code.djangoproject.com/ticket/36886>
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