Question

Hi I read a few post on this topic, lets say I want to delete every object for a given class db.model such as LinkRating2, is there a way to delete it on startup with a simple command? I thought i remember seeing this somewhere eg –clear datastore?, otherwise I have been trying various methods in sdk console but all seem to be memory crashing as the file is taking forever just to load and start I don’t think there is any memory left about lol. So what would be best code method to delete entire entity?

class LinkRating2(db.Model):
    user = db.StringProperty()
    link = db.StringProperty()
    rating2 = db.FloatProperty()

tried this but this is super slow

results2 = LinkRating2.all()
results = results2.fetch(500)

while results:
    db.delete(results)
    results = results2.fetch(500)

Answer 1

is there a way to delete it on startup
with a simple command? I thought i
remember seeing this somewhere eg
–clear datastore?

If you’re talking about the development server, yes. dev_appserver.py --clear_datastore myapp will start you up with a fresh datastore. This is the best option when you’re working locally.

I didn’t bother putting it in a while
loop, as trying to delete all of the
entities in one go probably stands a
good chance of exceeding the 30-second
deadline. You’ll just need to do this
until all of the entities are gone.

If you do want to wipe out every entity of a given type in production, this is a good excuse to use remote_api instead of writing a web-based handler, both to circumvent the 30 second deadline and to reduce the chance of your entitypocalypse code being run again by accident.

One last thing: if you want to delete some entities but you don’t want to bother loading the model definition, you can use the low level datastore API:

from google.appengine.api import datastore

kind = 'LinkRating2'
batch_size = 1000

query = datastore.Query(kind=kind, keys_only=True)
results = query.Get(batch_size)
while results:
  print "Deleting %d %s entities" % (batch_size, kind)
  datastore.Delete(results)
  results = query.Get(batch_size)