Cast numeric columns for order expression on SQLite

Closes #13397
(grafted from 97e889240413ac521a15dc81453499bb888039c0)

--HG--
branch : 7.0

trytond/trytond/model/fields/numeric.py

@@ -6,6 +6,7 @@ from sql import Cast, CombiningQuery, Literal, Select
 
 from trytond import backend
 
+from .field import order_method
 from .float import Float
 
 
@@ -17,6 +18,14 @@ class Numeric(Float):
     _sql_type = 'NUMERIC'
     _py_type = Decimal
 
+    @order_method
+    def convert_order(self, name, tables, Model):
+        columns = super().convert_order(name, tables, Model)
+        if backend.name == 'sqlite':
+            # Must be cast because Decimal is stored as bytes
+            columns = [Cast(c, self.sql_type().base) for c in columns]
+        return columns
+
     def _domain_column(self, operator, column):
         column = super()._domain_column(operator, column)
         if backend.name == 'sqlite':

trytond/trytond/tests/test_field_numeric.py

@@ -461,6 +461,28 @@ class FieldNumericTestCase(unittest.TestCase):
 
         self.assertEqual(numerics, [numeric1])
 
+    @with_transaction()
+    def test_search_order(self):
+        "Test search order"
+        pool = Pool()
+        Numeric = pool.get('test.numeric')
+
+        Numeric.create([{
+                    'numeric': Decimal('10.00'),
+                    }, {
+                    'numeric': Decimal('7.00'),
+                    }])
+
+        records_asc = Numeric.search([], order=[('numeric', 'ASC')])
+        records_desc = Numeric.search([], order=[('numeric', 'DESC')])
+
+        self.assertEqual(
+            [r.numeric for r in records_asc],
+            [Decimal('7.00'), Decimal('10.00')])
+        self.assertEqual(
+            [r.numeric for r in records_desc],
+            [Decimal('10.00'), Decimal('7.00')])
+
     @with_transaction()
     def test_write(self):
         "Test write numeric"