Hi Karan
the batch operation is a key.
http://googleappengine.blogspot.ru/2009/06/10-things-you-probably-didnt-know-about.html
5. You can batch put, get and delete operations for efficiency
Every time you make a datastore request, such as a query or a get()
operation, your app has to send the request off to the datastore, which
processes the request and sends back a response. This request-response
cycle takes time, and if you're doing a lot of operations one after the
other, this can add up to a substantial delay in how long your users have
to wait to see a result.
Fortunately, there's an easy way to reduce the number of round trips: batch
operations. The db.put(), db.get(), and db.delete() functions all accept
lists in addition to their more usual singular invocation. When passed a
list, they perform the operation on all the items in the list in a
singledatastore round trip and they are executed in parallel, saving you a
lot of time. For example, take a look at this common pattern:
for entity in MyModel.all().filter("color =",
old_favorite).fetch(100):
entity.color = new_favorite
entity.put()
Doing the update this way requires one datastore round trip for the query,
plus one additional round trip for each updated entity - for a total of up
to 101 round trips! In comparison, take a look at this example:
updated = []
for entity in MyModel.all().filter("color =",
old_favorite).fetch(100):
entity.color = new_favorite
updated.append(entity)
db.put(updated)
By adding two lines, we've reduced the number of round trips required from
101 to just 2!
also, see this thread:
https://groups.google.com/forum/#!topic/appengine-ndb-discuss/04wiYYI26pc
WBR, Vitaly
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