fix: sqlite decimal filter error with __gt (#2020)

Author: waketzheng

CHANGELOG.rst

@@ -16,6 +16,10 @@ Added
 ^^^^^
 - Add `create()` method to reverse ForeignKey relations, enabling `parent.children.create()` syntax
 
+Fixed
+^^^^^
+- Fix sqlite decimal filter error with `__gt` (#2020)
+
 0.25
 ====
 

tests/fields/test_decimal.py

@@ -62,6 +62,10 @@ async def test_filter(self):
             .first()
         )
         self.assertEqual(obj, obj0)
+        objs = await testmodels.DecimalFields.filter(decimal_nodec__gt=2).all()
+        self.assertIn(obj, objs)
+        objs = await testmodels.DecimalFields.filter(decimal_nodec__lt=100).all()
+        self.assertIn(obj, objs)
 
     async def test_f_expression_update(self):
         obj0 = await testmodels.DecimalFields.create(decimal=Decimal("1.23456"), decimal_nodec=18.7)

tortoise/expressions.py

@@ -387,6 +387,7 @@ def _process_filter_kwarg(
         else:
             filter_info = model._meta.get_filter(key)
 
+        field_object = None
         if "table" in filter_info:
             # join the table
             join = (
@@ -405,7 +406,14 @@ def _process_filter_kwarg(
                 else field_object.to_db_value(value, model)
             )
         op = filter_info["operator"]
-        criterion = op(table[filter_info.get("source_field", filter_info["field"])], value)
+        term: Term = table[filter_info.get("source_field", filter_info["field"])]
+        if field_object is not None:
+            func = field_object.get_for_dialect(
+                model._meta.db.capabilities.dialect, "function_cast"
+            )
+            if func is not None:
+                term = func(field_object, term)
+        criterion = op(term, value)
         return criterion, join
 
     def _resolve_regular_kwarg(