Refs #17260 -- Prevented Oracle timezone conversion from stripping microseonds.

    _tzname_re = re.compile(r'^[\w/:+-]+$')

    def _convert_field_to_tz(self, field_name, tzname):

        if settings.USE_TZ:

        if not settings.USE_TZ:

            return field_name

        if not self._tzname_re.match(tzname):

            raise ValueError("Invalid time zone name: %s" % tzname)

            # Convert from UTC to local time, returning TIMESTAMP WITH TIME ZONE.

            field_name = "(FROM_TZ(%s, '0:00') AT TIME ZONE '%s')" % (field_name, tzname)

        # Extracting from a TIMESTAMP WITH TIME ZONE ignore the time zone.

        # Convert to a DATETIME, which is called DATE by Oracle. There's no

        # built-in function to do that; the easiest is to go through a string.

        field_name = "TO_CHAR(%s, 'YYYY-MM-DD HH24:MI:SS')" % field_name

        field_name = "TO_DATE(%s, 'YYYY-MM-DD HH24:MI:SS')" % field_name

        # Re-convert to a TIMESTAMP because EXTRACT only handles the date part

        # on DATE values, even though they actually store the time part.

        return "CAST(%s AS TIMESTAMP)" % field_name

        # Convert from UTC to local time, returning TIMESTAMP WITH TIME ZONE

        # and cast it back to TIMESTAMP to strip the TIME ZONE details.

        return "CAST((FROM_TZ(%s, '0:00') AT TIME ZONE '%s') AS TIMESTAMP)" % (field_name, tzname)

    def datetime_cast_date_sql(self, field_name, tzname):

        field_name = self._convert_field_to_tz(field_name, tzname)

        elif lookup_type == 'minute':

            sql = "TRUNC(%s, 'MI')" % field_name

        else:

            sql = field_name    # Cast to DATE removes sub-second precision.

            sql = "CAST(%s AS DATE)" % field_name  # Cast to DATE removes sub-second precision.

        return sql, []

    def get_db_converters(self, expression):