sqlalchemy-mptt 0.5.0

SQLAlchemy mixins for implementing tree-like models using Modified Pre-order Tree Traversal (MPTT) / Nested Sets

Library for implementing Modified Preorder Tree Traversal with your SQLAlchemy Models and working with trees of Model instances, like django-mptt. Docs http://sqlalchemy-mptt.readthedocs.io/

The nested set model is a particular technique for representing nested sets (also known as trees or hierarchies) in relational databases.

Installing

Install from github:

pip install git+http://github.com/uralbash/sqlalchemy_mptt.git

PyPi:

pip install sqlalchemy_mptt

Source:

pip install -e .

Usage

Add mixin to model

from sqlalchemy import Column, Integer, Boolean
from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy_mptt.mixins import BaseNestedSets

Base = declarative_base()


class Tree(Base, BaseNestedSets):
    __tablename__ = "tree"

    id = Column(Integer, primary_key=True)
    visible = Column(Boolean)

    def __repr__(self):
        return "<Node (%s)>" % self.id

Now you can add, move and delete obj!

Insert node

node = Tree(parent_id=6)
session.add(node)

level           Nested sets example
1                    1(1)22
        _______________|___________________
       |               |                   |
2    2(2)5           6(4)11             12(7)21
       |               ^                   ^
3    3(3)4       7(5)8   9(6)10    13(8)16   17(10)20
                                      |          |
4                                  14(9)15   18(11)19

level     Insert node with parent_id == 6
1                    1(1)24
        _______________|_________________
       |               |                 |
2    2(2)5           6(4)13           14(7)23
       |           ____|____          ___|____
       |          |         |        |        |
3    3(3)4      7(5)8    9(6)12  15(8)18   19(10)22
                           |        |         |
4                      10(23)11  16(9)17  20(11)21

Delete node

node = session.query(Tree).filter(Tree.id == 4).one()
session.delete(node)

level           Nested sets example
1                    1(1)22
        _______________|___________________
       |               |                   |
2    2(2)5           6(4)11             12(7)21
       |               ^                   ^
3    3(3)4       7(5)8   9(6)10    13(8)16   17(10)20
                                      |          |
4                                  14(9)15   18(11)19

level         Delete node == 4
1                    1(1)16
        _______________|_____
       |                     |
2    2(2)5                 6(7)15
       |                     ^
3    3(3)4            7(8)10   11(10)14
                        |          |
4                     8(9)9    12(11)13

Update node

node = session.query(Tree).filter(Tree.id == 8).one()
node.parent_id = 5
session.add(node)

level           Nested sets example
    1                    1(1)22
            _______________|___________________
           |               |                   |
    2    2(2)5           6(4)11             12(7)21
           |               ^                   ^
    3    3(3)4       7(5)8   9(6)10    13(8)16   17(10)20
                                          |          |
    4                                  14(9)15   18(11)19

level               Move 8 - > 5
    1                     1(1)22
             _______________|__________________
            |               |                  |
    2     2(2)5           6(4)15            16(7)21
            |               ^                  |
    3     3(3)4      7(5)12   13(6)14      17(10)20
                       |                        |
    4                8(8)11                18(11)19
                       |
    5                9(9)10

Move node (support multitree)

Nested sets multitree

Move inside

node = session.query(Tree).filter(Tree.id == 4).one()
node.move_inside("15")

         4 -> 15
level           Nested sets tree1
1                    1(1)16
        _______________|_____________________
       |                                     |
2    2(2)5                                 6(7)15
       |                                     ^
3    3(3)4                            7(8)10   11(10)14
                                        |          |
4                                     8(9)9    12(11)13

level           Nested sets tree2
1                     1(12)28
         ________________|_______________________
        |                |                       |
2    2(13)5            6(15)17                18(18)27
       |                 ^                        ^
3    3(14)4    7(4)12 13(16)14  15(17)16  19(19)22  23(21)26
                 ^                            |         |
4          8(5)9  10(6)11                 20(20)21  24(22)25

Move after

node = session.query(Tree).filter(Tree.id == 8).one()
node.move_after("5")

level           Nested sets example
     1                    1(1)22
             _______________|___________________
            |               |                   |
     2    2(2)5           6(4)11             12(7)21
            |               ^                   ^
     3    3(3)4       7(5)8   9(6)10    13(8)16   17(10)20
                                           |          |
     4                                  14(9)15   18(11)19

 level               Move 8 after 5
     1                     1(1)22
              _______________|__________________
             |               |                  |
     2     2(2)5           6(4)15            16(7)21
             |               ^                  |
     3     3(3)4    7(5)8  9(8)12  13(6)14   17(10)20
                             |                  |
     4                    10(9)11            18(11)19

Move to top level

node = session.query(Tree).filter(Tree.id == 15).one()
node.move_after("1")

level           tree_id = 1
1                    1(1)22
        _______________|___________________
       |               |                   |
2    2(2)5           6(4)11             12(7)21
       |               ^                   ^
3    3(3)4       7(5)8   9(6)10    13(8)16   17(10)20
                                      |          |
4                                  14(9)15   18(11)19

level           tree_id = 2
1                     1(15)6
                         ^
2                 2(16)3   4(17)5

level           tree_id = 3
1                    1(12)16
         _______________|
        |               |
2    2(13)5          6(18)15
        |               ^
3    3(14)4     7(19)10   11(21)14
                   |          |
4               8(20)9    12(22)13

Support and Development

To report bugs, use the issue tracker.

We welcome any contribution: suggestions, ideas, commits with new futures, bug fixes, refactoring, docs, tests, translations, etc…

If you have any questions:

• Use the Discussion board

• Contact the maintainer via email: [e-mail]

• Contact the author via email: [e-mail] or #sacrud IRC channel

Refer the detailed contribution guide in the docs for more information on setting up the development environment, running tests, and contributing to the project.

License

The project is licensed under the MIT license.

Versions releases 0.2.x & above

0.5.0 (2025-11-18)

see issues #104 & #110

• Add support for SQLAlchemy 1.4.

• Drop official support for PyPy.

• Simplify memory management by using weakref.WeakSet instead of rolling our own weak reference set.

• Unify after_flush_postexec execution path for CPython & PyPy.

• Simplify get_siblings.

• Run doctest on all code snippets in the documentation.

• Fix some of the incorrect documentation snippets.

0.4.0 (2025-05-30)

see issue #97

• Support for Python 3.10 and 3.11

• Dropped support for Python 3.7

0.3.0 (2025-05-10)

see issues #63, #87, #89 & #90

• Support for joined-table inheritance

• Restrict to Python & PyPy 3.7 - 3.9

• Restrict to SQLA 1.0 - 1.3

• Fixes race condition with garbage collection on PyPy versions

0.2.5 (2019-07-23)

see issue #64

• Added similar django_mptt methods get_siblings and get_children

0.2.4 (2018-12-14)

see PR #61

• Allow to specify ordering of path_to_root

0.2.3 (2018-06-03)

see issue #57

• Fix rebuild tree

• Added support node’s identifier start from 0

0.2.2 (2017-10-05)

see issue #56

• Added custom default root level. Support Django style level=0

0.2.1 (2016-01-23)

see PR #51

• fix of index columns names

0.2.0 (2015-11-13)

see PR #50

• Changed parent_id to dynamically match the type of the primary_key

• exposed drilldown_tree’s logic and path_to_root’s logic as both instance and class level method