Hello,
I have a question regarding using a mapper to add a relation to a
mapped class using instance attributes (not contained in the mapped
classes table def) on the mapped class control the select statement
for the join.
For example:
my Calendar class has a relation to CalendarEvent
Calendar.map_table(calendar_table,
properties={'events':relation(CalendarEvent,backref='calendar',collection_class
= CalendarEventList)})
I would like to be able to control the where clause of the join the
mapper uses when the property is accessed with data from my Calendar
class that is not in the table definition, such as the time slice the
Calendar represents.
So something like:
Calendar.map_table(calendar_table,
properties={'events':relation(CalendarEvent,primaryjoin=and_(Calendar.c.id==CalendarEvent.c.calendar_id,
calendar.CalendarEvent.c.starttime >= ???{need
help}???)),backref='calendar',collection_class = CalendarEventList)})
so in a use case:
c = Calendar() [Assume fill from db]
c.event_list_start = datetime.now()
c.event_list_end = datetime.now() + timedelta(days=1)
and the mapper would have:
Calendar.map_table(calendar_table,properties={'events':relation(CalendarEvent,
primaryjoin=and_(
Calendar.c.space_id==calendar.CalendarEvent.c.calendar_id,
CalendarEvent.c.starttime >= Calendar.event_list_start,
CalendarEvent.c.endtime <= Calendar.event_list_end,
)),backref='calendar',collection_class = CalendarEventList)})
I am not sure if SQLalchemy supports this or if I am looking at this
the wrong way.
Thanks in advance,
Rob
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