fix(rtdb): Match backend key ordering in order_by_key() query results

firebase_admin/db.py

@@ -23,6 +23,7 @@
 import collections
 import json
 import os
+import re
 import sys
 import threading
 from urllib import parse
@@ -661,9 +662,13 @@ class _SortEntry:
     _type_string = 4
     _type_object = 5
 
+    # Matches child keys that the Realtime Database backend treats as integers when ordering.
+    _INTEGER_KEY_PATTERN = re.compile(r'^-?(0*)\d{1,10}$')
+
     def __init__(self, key, value, order_by):
         self._key = key
         self._value = value
+        self._order_by = order_by
         if order_by in ('$key', '$priority'):
             self._index = key
         elif order_by == '$value':
@@ -719,6 +724,28 @@ def _extract_child(cls, value, path):
                 return None
         return current
 
+    @classmethod
+    def _parse_int_key(cls, key):
+        """Returns key parsed as a 32-bit integer, or None if not parseable."""
+        if isinstance(key, str) and cls._INTEGER_KEY_PATTERN.match(key):
+            value = int(key)
+            if -2147483648 <= value <= 2147483647:
+                return value
+        return None
+
+    @classmethod
+    def _key_order(cls, key):
+        """Builds a sort key that orders child keys the way the backend does.
+
+        Keys parseable as 32-bit integers come first, in ascending numeric order (ties
+        broken by key length, shorter keys first). All other keys follow in lexicographic
+        order. See https://github.com/firebase/firebase-admin-python/issues/677
+        """
+        parsed = cls._parse_int_key(key)
+        if parsed is not None:
+            return (0, parsed, len(key), key)
+        return (1, key)
+
     def _compare(self, other):
         """Compares two _SortEntry instances.
 
@@ -727,6 +754,12 @@ def _compare(self, other):
         nor string, compare the keys. In all other cases compare based on the ordering provided
         by index types.
         """
+        if (self._order_by == '$key' and isinstance(self.key, str)
+                and isinstance(other.key, str)):
+            # Match the backend key ordering instead of a plain lexicographic sort.
+            this = _SortEntry._key_order(self.key)
+            that = _SortEntry._key_order(other.key)
+            return (this > that) - (this < that)
         self_key, other_key = self.index_type, other.index_type
         if self_key == other_key:
             if self_key in (self._type_numeric, self._type_string) and self.index != other.index:

tests/test_db.py

@@ -1100,6 +1100,17 @@ def test_invalid_sort(self, value):
         ({'k1' : 1, 'k2' : 2, 'k3' : 3}, ['k1', 'k2', 'k3']),
         ({'k3' : 3, 'k2' : 2, 'k1' : 1}, ['k1', 'k2', 'k3']),
         ({'k1' : 3, 'k3' : 1, 'k2' : 2}, ['k1', 'k2', 'k3']),
+        # Keys that parse as integers are ordered numerically, matching the backend
+        # (https://github.com/firebase/firebase-admin-python/issues/677).
+        ({'100001' : 1, '100002' : 2, '123' : 3, '100003' : 4},
+         ['123', '100001', '100002', '100003']),
+        ({'2' : 1, '10' : 2, '1' : 3}, ['1', '2', '10']),
+        ({'-5' : 1, '3' : 2, '-10' : 3}, ['-10', '-5', '3']),
+        ({'01' : 1, '1' : 2, '2' : 3}, ['1', '01', '2']),
+        # Integer keys come before string keys; the rest are lexicographic.
+        ({'b' : 1, '10' : 2, 'a' : 3, '2' : 4}, ['2', '10', 'a', 'b']),
+        # Keys outside the signed 32-bit integer range are ordered lexicographically.
+        ({'2147483648' : 1, '9' : 2, '2147483647' : 3}, ['9', '2147483647', '2147483648']),
     ])
     def test_order_by_key(self, result, expected):
         ordered = db._Sorter(result, '$key').get()