1   Counting

Every time, Google App Engine releases new version of SDK, I always read the release notes. I was aware of

Results of datastore count() queries and offsets for all datastore queries are no longer capped at 1000,

when version 1.3.6 was released. I wrote a quick code to test it, something like the followings:

count = TestModel.all().count()

data1 = TestModel.all().fetch(1100, offset=5)
data2 = TestModel.all().fetch(1, offset=1100)

Using 1.3.8, first part still got me 1000 at most. The second part, I could fetch more than 1000 entities, and the offset could be bigger than 1000 without problems.

I finally saw someone asked and the correct way is:

count = TestModel.all().count(limit=None)

Now, I am reading the documentation again:

count() has no maximum limit. If you dont specify a limit, the datastore continues counting until it finishes counting or times out.

This doesnt sound like the same behavior in development server. I didnt try it on production server.

(I used to use this way to count.)

2   Randomly fetching

Before 1.3.6, there are some ways to get a random entity from datastore. All suck and are awkward. Now offset can be supplied with number bigger then 1000. Does it resolve? Read this line first:

The query has performance characteristics that correspond linearly with the offset amount plus the limit.

Well, I dont care at this moment since none of my data are too large.

I think Google is Einstein and Google App Engine is Quantnum Theory. ;)