Unlimited-length character fields in Postgres perform the same as limited-length fields, and the Postgres manual suggests not arbitrarily limiting these fields. Unfortunately, Django does not provide a way to access unlimited-length character fields except using TextField, which is rendered differently in forms and in the admin, and has different connotations.
LongCharField is a way to avoid putting arbitrary max_length values where they aren't required. It will only work with databases that allow VARCHAR with no numeric parameters, such as Postgres. MySQL won't work.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | from django.db import models
from django.utils.translation import ugettext_lazy as _
class LongCharField(models.CharField):
"A basically unlimited-length CharField."
description = _("Unlimited-length string")
def __init__(self, *args, **kwargs):
kwargs['max_length'] = int(1e9) # Satisfy management validation.
super(models.CharField, self).__init__(*args, **kwargs)
# Don't add max-length validator like CharField does.
def get_internal_type(self):
# This has no function, since this value is used as a lookup in
# db_type(). Put something that isn't known by django so it
# raises an error if it is ever used.
return 'LongCharField'
def db_type(self, connection):
# *** This is probably only compatible with Postgres.
# 'varchar' with no max length is equivalent to 'text' in Postgres,
# but put 'varchar' so we can tell LongCharFields from TextFields
# when we're looking at the db.
return 'varchar'
def formfield(self, **kwargs):
# Don't pass max_length to form field like CharField does.
return super(models.CharField, self).formfield(**kwargs)
|
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Comments
It would be better to just stick with TextField and change it's widget. Your solution breaks db portability.
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Thanks. There are situations, in which you cannot use TextField instead of CharField. For example, when used with array aggregation, your postgre query might end up like this:
Thus, this game is also about database types.
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