Fixed #36030 - Divide an integer field by a constant decimal.Decimal returns inconsistent decimal (sqlite3 & postgre only)

django/db/backends/base/operations.py

@@ -658,7 +658,7 @@ class BaseDatabaseOperations:
         """
         return True
 
-    def combine_expression(self, connector, sub_expressions):
+    def combine_expression(self, connector, sub_expressions, output_field=None):
         """
         Combine a list of subexpressions into a single expression, using
         the provided connecting operator. This is required because operators

django/db/backends/mysql/operations.py

@@ -287,7 +287,7 @@ class DatabaseOperations(BaseDatabaseOperations):
     def pk_default_value(self):
         return "NULL"
 
-    def combine_expression(self, connector, sub_expressions):
+    def combine_expression(self, connector, sub_expressions, output_field=None):
         if connector == "^":
             return "POW(%s)" % ",".join(sub_expressions)
         # Convert the result to a signed integer since MySQL's binary operators
@@ -298,7 +298,9 @@ class DatabaseOperations(BaseDatabaseOperations):
         elif connector == ">>":
             lhs, rhs = sub_expressions
             return "FLOOR(%(lhs)s / POW(2, %(rhs)s))" % {"lhs": lhs, "rhs": rhs}
-        return super().combine_expression(connector, sub_expressions)
+        return super().combine_expression(
+            connector, sub_expressions, output_field=output_field
+        )
 
     def get_db_converters(self, expression):
         converters = super().get_db_converters(expression)

django/db/backends/postgresql/operations.py

@@ -420,3 +420,15 @@ class DatabaseOperations(BaseDatabaseOperations):
             rhs_expr = Cast(rhs_expr, lhs_field)
 
         return lhs_expr, rhs_expr
+
+    def combine_expression(self, connector, sub_expressions, output_field=None):
+        if (
+            connector == "/"
+            and output_field
+            and output_field.get_internal_type() in ("FloatField", "DecimalField")
+        ):
+            lhs, rhs = sub_expressions
+            return f"CAST({lhs} AS NUMERIC) / {rhs}"
+        return super().combine_expression(
+            connector, sub_expressions, output_field=output_field
+        )

django/db/backends/sqlite3/operations.py

@@ -363,14 +363,32 @@ class DatabaseOperations(BaseDatabaseOperations):
     def convert_booleanfield_value(self, value, expression, connection):
         return bool(value) if value in (1, 0) else value
 
-    def combine_expression(self, connector, sub_expressions):
+    def combine_expression(self, connector, sub_expressions, output_field=None):
         # SQLite doesn't have a ^ operator, so use the user-defined POWER
         # function that's registered in connect().
         if connector == "^":
             return "POWER(%s)" % ",".join(sub_expressions)
         elif connector == "#":
             return "BITXOR(%s)" % ",".join(sub_expressions)
-        return super().combine_expression(connector, sub_expressions)
+        elif connector == "/":
+            lhs, rhs = sub_expressions
+            # SQLite performs floating-point division. To ensure results match the
+            # expected output_field type:
+            # - For FloatField/DecimalField, ensure REAL division.
+            # - For other types (e.g. IntegerField), perform REAL division,
+            #   then ROUND and CAST to INTEGER to mimic integer division behavior.
+            if output_field and output_field.get_internal_type() in (
+                "FloatField",
+                "DecimalField",
+            ):
+                return f"CAST({lhs} AS REAL) / CAST({rhs} AS REAL)"
+            else:
+                return (
+                    f"CAST(ROUND(CAST({lhs} AS REAL) / CAST({rhs} AS REAL)) AS INTEGER)"
+                )
+        return super().combine_expression(
+            connector, sub_expressions, output_field=output_field
+        )
 
     def combine_duration_expression(self, connector, sub_expressions):
         if connector not in ["+", "-", "*", "/"]:

django/db/models/expressions.py

@@ -756,18 +756,29 @@ class CombinedExpression(SQLiteNumericMixin, Expression):
         return combined_type()
 
     def as_sql(self, compiler, connection):
+        # We need output_field for specific combined operations
+        # AND we don't want to block the run in case of None
+        try:
+            output_field = self.output_field
+        except FieldError:
+            output_field = None
+        sql, params = self._compile_expressions(compiler)
+        sql = self._handle_operator(sql, connection, output_field=output_field)
+        return f"({sql})", params
+
+    def _compile_expressions(self, compiler):
         expressions = []
-        expression_params = []
+        params = []
-        sql, params = compiler.compile(self.lhs)
+        for expr in [self.lhs, self.rhs]:
-        expressions.append(sql)
+            sql, param = compiler.compile(expr)
-        expression_params.extend(params)
+            expressions.append(sql)
-        sql, params = compiler.compile(self.rhs)
+            params.extend(param)
-        expressions.append(sql)
+        return expressions, params
-        expression_params.extend(params)
+
-        # order of precedence
+    def _handle_operator(self, expressions, connection, output_field=None):
-        expression_wrapper = "(%s)"
+        return connection.ops.combine_expression(
-        sql = connection.ops.combine_expression(self.connector, expressions)
+            self.connector, expressions, output_field=output_field
-        return expression_wrapper % sql, expression_params
+        )
 
     def resolve_expression(
         self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False

tests/expressions/tests.py

@@ -1599,6 +1599,46 @@ class ExpressionsNumericTests(TestCase):
         n.refresh_from_db()
         self.assertEqual(n.decimal_value, Decimal("0.1"))
 
+    def test_decimal_division_precision(self):
+        """Test that division with Decimal preserves precision"""
+        obj = Number.objects.create(integer=2)
+        qs = Number.objects.annotate(
+            ratio=ExpressionWrapper(
+                F("integer") / Value(3.0),
+                output_field=DecimalField(max_digits=10, decimal_places=4),
+            )
+        ).filter(pk=obj.pk)
+        self.assertAlmostEqual(
+            float(qs.get().ratio),
+            float(Decimal("2") / Decimal("3")),
+            places=4,
+            msg="Division should preserve decimal precision",
+        )
+
+    def test_decimal_division_types(self):
+        """Test that division with Decimal preserves numeric type"""
+        Number.objects.all().delete()
+        for num, den, expected in [
+            (2, Decimal("3"), "0.6667"),
+            (5, Decimal("2"), "2.5000"),
+            (1, Decimal("3"), "0.3333"),
+        ]:
+            with self.subTest(num=num, den=den):
+                number = Number.objects.create(integer=num)
+                qs = Number.objects.filter(pk=number.pk).annotate(
+                    ratio=ExpressionWrapper(
+                        F("integer") / Value(den, output_field=DecimalField()),
+                        output_field=DecimalField(max_digits=10, decimal_places=4),
+                    )
+                )
+                result = qs.get()
+                self.assertAlmostEqual(
+                    float(result.ratio),
+                    float(expected),
+                    places=4,
+                    msg=f"Divide {num} by {den} should give result: {expected}",
+                )
+
 
 class ExpressionOperatorTests(TestCase):
     @classmethod