mariocesar / django-ltree

An ltree extension implementation to support hierarchical tree-like data using the native Postgres extension ltree in django models

django-ltree

A tree extension implementation to support hierarchical tree-like data in Django models, using the native Postgres extension ltree.

Postgresql has already a optimized and very useful tree implementation for data. The extension is ltree

This fork contains a backport to Django 1.11 and Python 3.6.

Links

• Pypi https://pypi.org/project/django-ltree/
• Source code https://github.com/mariocesar/django-ltree
• Bugs https://github.com/mariocesar/django-ltree/issues
• Contribute https://github.com/mariocesar/django-ltree/pulls
• Documentation TODO

Install

pip install django-ltree

Then add django_ltree to INSTALLED_APPS in your Django project settings.

And make sure to run django_ltree migrations before you added the PathField

python manage.py migrate django_ltree

django_ltree migrations will install the ltree extension if not exist.

You can alternatively specify the django_ltree dependency in the migrations of your applications that requires PathField, and run migrations smoothly.

class Migration(migrations.Migration):
    dependencies = [
            ('django_ltree', '__latest__'),
    ]

Requires

• Django 1.11 or superior
• Python 2

Testing

Make sure you have Postgres installed. Then simply run tox in the root directory of the project.

django-ltree's Issues

NLevel transform is not registered as a lookup

Currently, the NLevel transform (functions.py) is not registered as a lookup. This means, that queries like MyModel.objects.filter(path__depth=NLevel(self.path)) won't work:

Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "C:\Users\user\.virtualenvs\backend-BawPrnSu\lib\site-packages\django\db\models\manager.py", line 82, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "C:\Users\user\.virtualenvs\backend-BawPrnSu\lib\site-packages\django\db\models\query.py", line 892, in filter
    return self._filter_or_exclude(False, *args, **kwargs)
  File "C:\Users\user\.virtualenvs\backend-BawPrnSu\lib\site-packages\django\db\models\query.py", line 910, in _filter_or_exclude
    clone.query.add_q(Q(*args, **kwargs))
  File "C:\Users\user\.virtualenvs\backend-BawPrnSu\lib\site-packages\django\db\models\sql\query.py", line 1290, in add_q
    clause, _ = self._add_q(q_object, self.used_aliases)
  File "C:\Users\user\.virtualenvs\backend-BawPrnSu\lib\site-packages\django\db\models\sql\query.py", line 1318, in _add_q
    split_subq=split_subq, simple_col=simple_col,
  File "C:\Users\user\.virtualenvs\backend-BawPrnSu\lib\site-packages\django\db\models\sql\query.py", line 1251, in build_filter
    condition = self.build_lookup(lookups, col, value)
  File "C:\Users\user\.virtualenvs\backend-BawPrnSu\lib\site-packages\django\db\models\sql\query.py", line 1110, in build_lookup
    lhs = self.try_transform(lhs, lookup_name)
  File "C:\Users\user\.virtualenvs\backend-BawPrnSu\lib\site-packages\django\db\models\sql\query.py", line 1151, in try_transform
    "permitted%s" % (name, output_field.__name__, suggestion)
django.core.exceptions.FieldError: Unsupported lookup 'depth' for PathField or join on the field not permitted.

Registering the lookup before running the query fixes this:
PathField.register_lookup(NLevel)

Is there a reason why this is missing?

Django 2.2.6
Python 3.6.5
django-ltree 0.4

Compatibility with Django3

Hi there!

Thanks for creating this extension :)

I encountered an issue when updating our project to Django3 (Python: 3.6, Django: 3.0.3).

I don't use the querysets methods directly, but rather the lookups:

units = Unit.objects.filter(path__descendants=path)  # path is an instance of PathValue

It used to work fine, but since our migration to Django3, we get the following issue:

  File "/usr/local/lib/python3.6/site-packages/django/db/models/sql/query.py", line 1074, in resolve_lookup_value
    for sub_value in value
  File "/usr/local/lib/python3.6/site-packages/django_ltree/fields.py", line 15, in __init__
    raise ValueError("Invalid value for path: {}".format(val))
ValueError: Invalid value for path: <generator object Query.resolve_lookup_value.<locals>.<genexpr> at 0x7fbeedd42d00>

The "culprit" is this line: https://github.com/django/django/blob/master/django/db/models/sql/query.py#L1067

As PathValue extends list, in the above code, it is instantiated with a generator object, which is not accepted by PathValue constructor.

For now, as a workaround, I cast all paths to string before using them in my queries, which seems to work quite well, but being able to use PathValue instances was rather practical.

I would be happy to work on a PR to fix this issue, but I'm not sure what would be the best way to proceed:

• Stop extending list?
• Allowing a generator object in PathValue constructor?

Let me know if I can help!

is there a tox to indicate the django and python versions that are compatible?

What is the purpose of slug?

This seems to cause an error when calling the add_child method from the TreeModel instance.
I think may the below line should be removed?

django-ltree/django_ltree/models.py

Line 51 in 154c7e3

kwargs["slug"] = slug

PathValue should be usable in dict and set

When dealing with trees, it's quite common to use a dictionary to label nodes, using the path as the key. Currently this can be accomplished by casting the path to str, but this introduces a lot of unnecessary casts.

Ideally, PathValue should extend tuple instead of list, but since this would be a breaking change, perhaps it's better to implement __hash__ on PathValue?

I'd imagine most code would treat paths as immutable anyway.

Thoughts?

I'd be happy to submit a PR implementing whatever you decide is the best course of action.

Possible bug at this line where str should be value in `"/" if "/" in str else "."`

Over in this line

django-ltree/django_ltree/fields.py

Line 13 in 154c7e3

split_by = "/" if "/" in str else "."

When i run python3.7 this doesn't seem to trigger any issue but when I upgrade to python3.8 in my django app, I get this error.

File "/usr/local/lib/python3.8/dist-packages/django_ltree/fields.py", line 13, in __init__
    split_by = "/" if "/" in str else "."
TypeError: argument of type 'type' is not iterable

Admin panel doesnot work with paths that start with an integer

Hi,

The regex pattern in

django-ltree/django_ltree/fields.py

Lines 53 to 57 in 154c7e3

	path_label_validator = RegexValidator(
	r"^(?P<root>[a-zA-Z][a-zA-Z0-9_]*)(?:.[a-zA-Z|a-zA-Z0-9_]+)*$",
	"A label is a sequence of alphanumeric characters and underscores separated by dots.",
	"invalid",
	)

Is not right.

It matches things like exampleIdentifier.group1.group2.group3 but not 0001.0000.000a ( which is the default generated paths for django-ltree )

In order to solve this change the regex to (?P<root>[a-zA-Z][a-zA-Z0-9_]*|\d+)(?:\.[a-zA-Z0-9_]+)*$ which accepts paths starting with an integer.

Thanks a bunch :D

more documentation on how to use this library better?

I have this exact code snippet and the migration is successful.

from core.models import PersonStampedModel
from django_ltree.fields import PathField
from model_utils.models import SoftDeletableModel, TimeStampedModel
from organizations.managers import OrganizationOwnedSoftDeletableManager
from organizations.models import OrganizationOwnedModel
from partial_index import PQ, PartialIndex


class WorkBreakdownStructure(
    TimeStampedModel, SoftDeletableModel, PersonStampedModel, OrganizationOwnedModel
):
    wbs_number = PathField(primary_key=True, editable=True)

    objects = OrganizationOwnedSoftDeletableManager()

    unique_field_in_organization = "wbs_number"

    def __str__(self):
        return str(self.wbs_number)

    class Meta:
        indexes = [
            PartialIndex(
                fields=["wbs_number", "organization"], unique=True, where=PQ(is_removed=False)
            )
        ]

I wanted to quickly bulk create the following records:

ABC20.12345.50000 - ABC20.12345.51000

I was wondering if there's some documentation on how to do this.

versions

Django: v2.2.9
Python: v3.6
postgres: v10

Write documentation?

Hi, Is there an ETA for the documentation?

Hard fork at `django-ltree-2`

Hi,

I don't think this repository is in development anymore, I have a fork at django-ltree-2 which addresses :

• #16
• #15
• #20

Along with some new features available in python :

• baseplate-admin/django-ltree-2#3
• baseplate-admin/django-ltree-2#4
• baseplate-admin/django-ltree-2#11

Along with automatic label generation

• baseplate-admin/django-ltree-2#6

Along with documentation

• https;//django-ltree-2.readthedocs.io

The test suits are identical. The project is a drop in replacement for django-ltree.

I am open to collaborations, if django-ltree is open to development, I will archive the fork.

Thanks a bunch