Hi,
In many cases, it could be useful to know the number of rows in a table (a kind) in a datastore using Google Application Engine.
There is not clear and fast solution . At least I have not found one.. Have you?
Hi,
In many cases, it could be useful to know the number of rows in a table (a kind) in a datastore using Google Application Engine.
There is not clear and fast solution . At least I have not found one.. Have you?
You can efficiently get a count of all entities of a particular kind (i.e., number of rows in a table) using the Datastore Statistics API. Simple example:
from google.appengine.ext.db import stats
kind_stats = stats.KindStat().all().filter("kind_name =", "NameOfYourModel").get()
count = kind_stats.count
You can find a more detailed example of how to get the latest stats here (GAE may keep multiple copies of the stats - one for 5min ago, one for 30min ago, etc.).
Note that these statistics aren't constantly updated so they lag a little behind the actual counts. If you really need the actual count, then you could track counts in your own custom stats table and update it every time you create/delete an entity (though this will be quite a bit more expensive to do).
There's no concept of "Select count(*)" in App Engine. You'll need to do one of the following: