Work on automatic label generation (#6)

* add

* Update paths.py

* lets see

* Revert "lets see"

This reverts commit 7633fac.

* Revert "Revert "lets see""

This reverts commit 5238e6a.

* Update paths.py

* Update paths.py

* add

* Update guess_label_size.py

add

Update guess_label_size.py

Update guess_label_size.py

Update guess_label_size.py

add

* Update guess_label_size.py

add

Update guess_label_size.py

Update guess_label_size.py

Update guess_label_size.py

add

* Update paths.py

* Update paths.py

* Update paths.py

* Update paths.py

* Update paths.py

* Update paths.py

* Update paths.py

Update paths.py

* Update paths.py

* Update paths.py

* Update paths.py

* add

add

Update test_label_generation.py

django_ltree/managers.py

@@ -27,7 +27,6 @@ def create_child(self, parent=None, **kwargs):
         path_generator = PathGenerator(
             prefix,
             skip=paths_in_use.values_list("path", flat=True),
-            label_size=getattr(self.model, "label_size"),
         )
         kwargs["path"] = path_generator.next()
         return self.create(**kwargs)

django_ltree/paths.py

@@ -1,18 +1,21 @@
 import string
+import math
 from itertools import product
 
-from django_ltree.fields import PathValue
+from .fields import PathValue
 
 
 class PathGenerator(object):
-    _default_label_size = 6  # Postgres limits this to 256
+    def __init__(self, prefix=None, skip=None):
+        combinations = string.digits + string.ascii_letters
 
-    def __init__(self, prefix=None, skip=None, label_size=None):
         self.skip_paths = [] if skip is None else skip[:]
         self.path_prefix = prefix if prefix else []
         self.product_iterator = product(
-            string.digits + string.ascii_letters,
-            repeat=label_size or self._default_label_size,
+            combinations,
+            repeat=self.guess_the_label_size(
+                path_size=len(self.skip_paths), combination_size=len(combinations)
+            ),
         )
 
     def __iter__(self):
@@ -26,3 +29,31 @@ def __next__(self):
                 return path
 
     next = __next__
+
+    @staticmethod
+    def guess_the_label_size(path_size: int, combination_size: int) -> int:
+        # The theoritical limit for this at the time of writing is 2_538_557_185_841_324_496 (python 3.12.2)
+        calculated_path_size = -1  # -1 is here for 0th index items
+        # The theoritical limit for this at the time of writing is 32 (python 3.12.2)
+        label_size = 0
+
+        # THIS IS AN VERY IMPORTANT CHECK
+        last = 0
+
+        while True:
+            possible_cominations = math.comb(combination_size, label_size)
+            if last > possible_cominations:
+                raise ValueError("We approached the limit of `math.comb`")
+
+            last = possible_cominations
+            calculated_path_size += possible_cominations
+
+            if calculated_path_size > path_size and label_size != 0:
+                break
+
+            label_size += 1
+
+        return label_size
+
+
+print(PathGenerator.guess_the_label_size(62, 62))

tests/taxonomy/models.py

@@ -4,9 +4,7 @@
 
 
 class Taxonomy(TreeModel):
-    label_size = 2
-
     name = models.TextField()
 
     def __str__(self):
-        return '{}: {}'.format(self.path, self.name)
+        return f"{self.path}: {self.name}"

tests/test_label_generation.py

@@ -0,0 +1,13 @@
+from django_ltree.paths import PathGenerator
+
+
+def test_label_generation():
+    assert PathGenerator.guess_the_label_size(62, 62) == 2
+    assert PathGenerator.guess_the_label_size(0, 62) == 1
+
+
+def test_automatic_name_creation():
+    from taxonomy.models import Taxonomy
+
+    for i in range(0, 1000):
+        Taxonomy.objects.create_child(name=i)