How to delete all datastore in Google App Engine?

Question

If you're talking about the live datastore, open the dashboard for your app (login on appengine) then datastore --> dataviewer, select all the rows for the table you want to delete and hit the delete button (you'll have to do this for all your tables). You can do the same programmatically through the remote_api (but I never used it).

If you're talking about the development datastore, you'll just have to delete the following file: "./WEB-INF/appengine-generated/local_db.bin". The file will be generated for you again next time you run the development server and you'll have a clear db.

Make sure to clean your project afterwards.

This is one of the little gotchas that come in handy when you start playing with the Google Application Engine. You'll find yourself persisting objects into the datastore then changing the JDO object model for your persistable entities ending up with obsolete data that'll make your app crash all over the place.

The best approach is the remote API method as suggested by Nick, he's an App Engine engineer from Google, so trust him.

It's not that difficult to do, and the latest 1.2.5 SDK provides the remote_shell_api.py out of the shelf. So go to download the new SDK. Then follow the steps:

• connect remote server in your commandline: remote_shell_api.py yourapp /remote_api The shell will ask for your login info, and if authorized, will make a Python shell for you. You need setup url handler for /remote_api in your app.yaml

• fetch the entities you'd like to delete, the code looks something like:

    from models import Entry
    query = Entry.all(keys_only=True)
    entries =query.fetch(1000)
    db.delete(entries)
    \# This could bulk delete 1000 entities a time

Update 2013-10-28:

• remote_shell_api.py has been replaced by remote_api_shell.py, and you should connect with remote_api_shell.py -s your_app_id.appspot.com, according to the documentation.

• There is a new experimental feature Datastore Admin, after enabling it in app settings, you can bulk delete as well as backup your datastore through the web ui.

The fastest and efficient way to handle bulk delete on Datastore is by using the new mapper API announced on the latest Google I/O.

If your language of choice is Python, you just have to register your mapper in a mapreduce.yaml file and define a function like this:

from mapreduce import operation as op
def process(entity):
 yield op.db.Delete(entity)

On Java you should have a look to this article that suggests a function like this:

@Override
public void map(Key key, Entity value, Context context) {
    log.info("Adding key to deletion pool: " + key);
    DatastoreMutationPool mutationPool = this.getAppEngineContext(context)
            .getMutationPool();
    mutationPool.delete(value.getKey());
}

EDIT:
Since SDK 1.3.8, there's a Datastore admin feature for this purpose

You can clear the development server datastore when you run the server:

/path/to/dev_appserver.py --clear_datastore=yes myapp

You can also abbreviate --clear_datastore with -c.

If you have a significant amount of data, you need to use a script to delete it. You can use remote_api to clear the datastore from the client side in a straightforward manner, though.