Google AppEngine

Actually, remote_api now supports almost all App Engine's APIs. An exception is the Users API, which is fairly useless over remote_api. :)

Just set up remote_api for your app using the directions here - notably the tip: Tip: If you have a Java app, you can use the Python bulkloader.py tool by installing the Java version of the remote_api handler, which is included with the Java runtime environment. The handler servlet class is com.google.apphosting.utils.remoteapi.RemoteApiServlet. Then, use the Python bulkloader with --dump or --restore.

-dump --k

You can optimise it further, however: For each favorite, create a 'UserFavorite' entity as a child entity of the relevant Story entry (or equivalently, as a child entity of a UserInfo entry), with the key name set to the user's unique ID. This way, you can determine if a user has favorited a story with a simple get: UserFavorite.get_by_name(user_id, parent=a_story) get operations are 3 to 5 times faster than queries, so this is a substantial improvement.

The data loader feature communicates with your application running on App Engine using remote_api, a request handler included with the App Engine runtime environment that allows remote applications with the proper credentials to access the datastore remotely. To use remote_api, you must map a URL to it.

I am trying to dump the data created in a Java app engine application.  So, I have two versions of the app - the live java version and the python version that hosts /remote_api .  (this caused the url confusion)

Perhaps you can try specifying app_id explicitly by adding "--app-id='yourappid'".

A query like this will use the merge join strategy by default. If it's too slow for the merge join strategy, you could have to build a custom index for it, which would indeed be 'exploding'  - each User entity would have len(friends)*len(likes) index entries.

Tip: If you have a Java app, you can use the Python bulkloader.py tool by installing the Java version of the remote_api handler, which is included with the Java runtime environment. The handler servlet class is com.google.apphosting.utils.remoteapi.RemoteApiServlet.

Now you can choose to put this in an existing version of your applications config.ru. Or you can choose to put it in a new version (ie. version just for bulk upload/download without your application code). Either way once a version with the RemoteApiServlet is uploaded run this command to download your data: bulkloader.py --dump --app_id="application id" --url="url_to_remote_api_servlet" --filename="file to download data to" Here is an example from one of my apps: bulkloader.py --dump --app_id=jsm277 --url=http://bulkmove.latest.jsm277.appspot.com/remote_api --filename=test_download_data This command will download every object in your applications Datastore. If you only want to download the objects of one kind then simple add the --kind= option. Another example: bulkloader.py --dump --app_id=jsm277 --url=http://bulkmove.latest.jsm277.appspot.com/remote_api --filename=test_download_data --kind=Posts In order to restore the data that you have just downloaded use this command: bulkloader.py --restore --url="url_to_remote_api_servlet" --filename="file name from dump command" --app_id="application id" Here is an example command: bulkloader.py --restore --url=http://bulkmove.latest.railsturbinetest.appspot.com/remote_api --filename=test_download_data --app_id=railsturbinetest There are several important thing to keep in mind when restoring the Datastore objectes. The restore command simple restores whatever is in the filename that you provide. So it does not matter if you dump your entire Datastore or just one kind you use the same command to restore them both. You can restore Datastore objects to a different application then the one that they were downloaded from. However, is important to keep in mind that the object's key is used to restore each object. So if there already esists an object in the Datastore with the same key as an object that is being restored the object in the Datastore will be overwritten The bulkloader.py is a good tool for moving data between applications on the Google App Engine and for locally backing up your data. However, it is not good for data conversion or manipulation in anyway since the data is stored in a binary form. So happy data moving.