To make things short, I have to make a script in Second Life communicating with an AppEngine app updating records in an ndb database. Records extracted from the database are sent as a batch (a page) to the LSL script, which updates customers, then asks the web app to mark these customers as updated in the database.
To create the batch I use a query on a (integer) property update_ver==0 and use fetch_page() to produce a cursor to the next batch. This cursor is also sent as urlsafe()-encoded parameter to the LSL script.
To mark the customer as updated, the update_ver is set to some other value like 2, and the entity is updated via put_async(). Then the LSL script fetches the next batch thanks to the cursor sent earlier.
My rather simple question is: in the web app, since the query property update_ver no longer satisfies the filter, is my cursor still valid ? Or do I have to use another strategy ?
Stripping out irrelevant parts (including authentication), my code currently looks like this (Customer is the entity in my database).
class GetCustomers(webapp2.RequestHandler): # handler that sends batches to the update script in SL
def get(self):
cursor=self.request.get("next",default_value=None)
query=Customer.query(Customer.update_ver==0,ancestor=customerset_key(),projection=[Customer.customer_name,Customer.customer_key]).order(Customer._key)
if cursor:
results,cursor,more=query.fetch_page(batchsize,start_cursor=ndb.Cursor(urlsafe=cursor))
else:
results,cursor,more=query.fetch_page(batchsize)
if more:
self.response.write("more=1\n")
self.response.write("next={}\n".format(cursor.urlsafe()))
else:
self.response.write("more=0\n")
self.response.write("n={}\n".format(len(results)))
for c in results:
self.response.write("c={},{},{}\n".format(c.customer_key,c.customer_name,c.key.urlsafe()))
self.response.set_status(200)
The handler that updates Customer entities in the database is the following. The c= parameters are urlsafe()-encoded entity keys of the records to update and the nv= parameter is the new version number for their update_ver property.
class UpdateCustomer(webapp2.RequestHandler):
@ndb.toplevel # don't exit until all async operations are finished
def post(self):
updatever=self.request.get("nv")
customers=self.request.get_all("c")
for ckey in customers:
cust=ndb.Key(urlsafe=ckey).get()
cust.update_ver=nv # filter in the query used to produce the cursor was using this property!
cust.update_date=datetime.datetime.utcnow()
cust.put_async()
else:
self.response.set_status(403)
Will this work as expected ? Thanks for any help !