Add sql_cast on Field

issue7266
review37141002

CHANGELOG

@@ -1,3 +1,5 @@
+* Add sql_cast on Field
+
 Version 4.8.0 - 2018-04-23
 * Bug fixes (see mercurial logs for details)
 * Add index method to order field set calls

doc/ref/models/fields.rst

@@ -180,6 +180,10 @@ Instance methods:
     For the list of supported types by Tryton see 
     :ref:`backend types <topics-backend_types>`.
 
+.. method:: Field.sql_cast(expression)
+
+    Return the SQL expression with cast with the type of the field.
+
 .. method:: Field.sql_column(table)
 
     Return the Column instance based on table.

trytond/model/fields/date.py

@@ -1,10 +1,27 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
 import datetime
+from sql.functions import Function
 
+from ... import backend
 from .field import Field
 
 
+class SQLite_Date(Function):
+    __slots__ = ()
+    _function = 'DATE'
+
+
+class SQLite_DateTime(Function):
+    __slots__ = ()
+    _function = 'DATETIME'
+
+
+class SQLite_Time(Function):
+    __slots__ = ()
+    _function = 'TIME'
+
+
 class Date(Field):
     '''
     Define a date field (``date``).
@@ -29,6 +46,11 @@ class Date(Field):
                 % (type(value), type(self)))
         return value
 
+    def sql_cast(self, expression):
+        if backend.name() == 'sqlite':
+            return SQLite_Date(expression)
+        return super(Date, self).sql_cast(expression)
+
 
 class DateTime(Field):
     '''
@@ -65,6 +87,11 @@ class DateTime(Field):
                 % (type(value), type(self)))
         return value.replace(microsecond=0)
 
+    def sql_cast(self, expression):
+        if backend.name() == 'sqlite':
+            return SQLite_DateTime(expression)
+        return super(DateTime, self).sql_cast(expression)
+
 
 class Timestamp(Field):
     '''
@@ -111,6 +138,11 @@ class Time(DateTime):
                 % (type(value), type(self)))
         return value.replace(microsecond=0)
 
+    def sql_cast(self, expression):
+        if backend.name() == 'sqlite':
+            return SQLite_Time(expression)
+        return super(Time, self).sql_cast(expression)
+
 
 class TimeDelta(Field):
     '''

trytond/model/fields/field.py

@@ -4,7 +4,7 @@ import warnings
 from functools import wraps
 
 from sql import (operators, Column, Literal, Select, CombiningQuery, Null,
-    Query, Expression)
+    Query, Expression, Cast)
 from sql.conditionals import Coalesce, NullIf
 from sql.operators import Concat
 
@@ -314,6 +314,9 @@ class Field(object):
         database = Transaction().database
         return database.sql_type(self._sql_type)
 
+    def sql_cast(self, expression):
+        return Cast(expression, self.sql_type().base)
+
     def sql_column(self, table):
         return Column(table, self.name)