Hi,
I want to implement aggregate functions like sum and avg in Java in
Google App Engine.
So as suggested in the forum I created a method to retrieve all the
records in a List and then calculating the sum and avg on a particular
field.It works well up to 20000 records  but for large number of
records (50000) ,it gives HardDeadlineExceededError.( request takes
more than 30 seconds to complete).
So how could we remove this error?

We even thought of second approach for aggregate functions.
Create an entity with entity name , field name on which aggregate
function required , aggregate function name and value of that
function. So we need to populate this entity or update this entity
every time we insert  or update a record in an entity. But this
approach also has some problems like:-
1. As this entity will be a root entity, it cannot be updated in the
transaction with other entity groups.
2. If we want to retrieve sum and avg with some conditions, it will
not get possible in this approach.

If anybody has some pointers how to cope up with these issues, please
give your suggestions.
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