Google App引擎：Golang datastore.GetAll（）无法正常工作

Once a week a cron job calls the following function in one of my app engine projects:

func cleanMealsFromDatabase(context appengine.Context) error {
    query := datastore.NewQuery("Essen").Limit(1000).KeysOnly()
    keys, err := query.GetAll(context, nil)
    if err != nil {
        return err
    }
    return datastore.DeleteMulti(context, keys)
}

I'm trying to batch delete a bunch of datastore entities. The function gets called correctly, but

query.GetAll(context, nil)

seems to always return an error. Am I doing something wrong?

Okay, I now know what went wrong. When I finally figured out how to log an error in app engine, it said:

API error 1 (datastore_v3: BAD_REQUEST): cannot write more than 500 entities in a single call

So all I had to do, was to change the Limit parameter from 1000 to 500 like this:

query := datastore.NewQuery("Essen").Limit(500).KeysOnly()

Now it works like intended.