Compressed model field for Django

README.md

Please note that storing compressed binary values inside database has its own disadvantage. According to my experience using PostgreSQL, it increased the size of custom-format dump (pg_dump -Fc) by 60%.

compressed_text_field.py

import zlib

from django.db import models
from jsonfield.fields import JSONFieldMixin



class CompressedTextField(models.BinaryField):
    """
    Model field for storing text as compressed binary data. Compression is done using zlib.
    """

    def _check_str_default_value(self):
        return []

    def from_db_value(self, value, expression, connection):
        if value is None:
            return value
        return zlib.decompress(value).decode()

    def to_python(self, value):
        if isinstance(value, bytes):
            return zlib.decompress(value).decode()
        return value

    def get_prep_value(self, value):
        return zlib.compress(value.encode())


class CompressedJSONField(JSONFieldMixin, models.BinaryField):
    """
    Same as JSONField, but uses zlib to store value as compressed binary data.
    """

    def _check_str_default_value(self):
        return []

    def from_db_value(self, value, expression, connection):
        if value is None:
            return value
        return super().from_db_value(zlib.decompress(value).decode(), expression, connection)

    def to_python(self, value):
        if isinstance(value, bytes):
            return super().to_python(zlib.decompress(value).decode())
        return super().to_python(value)

    def get_prep_value(self, value):
        return zlib.compress(super().get_prep_value(value).encode())