fix: clamp count() at 0 when offset exceeds total

CHANGELOG.rst

@@ -21,6 +21,7 @@ Added
 Fixed
 ^^^^^
 - ``MigrationRecorder`` now uses parameterized queries; fixes MariaDB/MySQL rejecting ISO-8601 ``applied_at`` values. (#2132)
+- ``QuerySet.count()`` no longer returns a negative number when ``offset()`` is greater than the total row count; it now returns ``0``.
 
 1.1.7
 -----

tests/test_queryset.py

@@ -106,6 +106,16 @@ async def test_offset_count(db, intfields_data):
     assert await IntFields.all().offset(10).count() == 20
 
 
+@pytest.mark.asyncio
+async def test_offset_count_beyond_total(db, intfields_data):
+    # An offset past the total must report 0, not a negative count (the SQL
+    # LIMIT/OFFSET would return zero rows).
+    assert await IntFields.all().offset(100).count() == 0
+    assert await IntFields.all().offset(100).count() == len(
+        await IntFields.all().offset(100)
+    )
+
+
 @pytest.mark.asyncio
 async def test_offset_negative(db, intfields_data):
     with pytest.raises(ParamsError, match="Offset should be non-negative number"):

tortoise/queryset.py

@@ -1571,7 +1571,10 @@ async def _execute(self) -> int:
         _, result = await self._db.execute_query(*self.query.get_parameterized_sql())
         if not result:
             return 0
-        count = list(dict(result[0]).values())[0] - self._offset
+        # COUNT(*) ignores LIMIT/OFFSET, so the offset is applied here. Clamp at
+        # 0: when the offset is past the total, SQL would return 0 rows, not a
+        # negative count.
+        count = max(0, list(dict(result[0]).values())[0] - self._offset)
         if self._limit and count > self._limit:
             return self._limit
         return count