Unlimited input for django admin with single line input widget

charfield_unlimited.py

import sys

from django.db.models import CharField


class CharFieldUnlimited(CharField):
    """Postgres specific varchar field
    Use this over models.TextField when you want a one line input in the django
    admin instead of the multi-line TextArea input widget.
    Using this field gives you unlimited length CharFields, whilst still using
    the default django (admin) widgets, so you still have a one line TextInput.
    In postgres, if a varchar field is specified without a length, it can store
    strings of any size, see:
    https://www.postgresql.org/docs/8.0/datatype-character.html
    Under the hood varchar and text in postgres are implemented as varlena, so
    there is no difference in their implementation (apart from the length check)
    http://www.varlena.com/varlena.php
    https://www.depesz.com/2010/03/02/charx-vs-varcharx-vs-varchar-vs-text/
    https://tapoueh.org/blog/2018/04/postgresql-data-types-text-processing/
    """

    def __init__(self, *args, **kwargs):
        # Set our default max_length to pythons sys.maxsize
        # Since we still need a max length for the django based model and form
        # checks, we specify sys.maxsize. This means that the
        # autogenerated django admin forms (which have MaxLengthValidators)
        # will continue to work.
        defaults = {'max_length': sys.maxsize}
        defaults.update(kwargs)
        super().__init__(*args, **defaults)

    def db_type(self, connection):
        return 'varchar'