This is an ultra-simplified example of how to delete old entities from the App Engine Datastore. The first 3 lines of code retrieves the current date, then subtracts 60 days from the current time (the multiplication converts days to milliseconds). DATE_PROPERTY_ON_ENTITY is the date property on the entity – when first writing the entity to the datastore, add the current date as a property. ENTITY_KIND is the entity kind we’re deleting.
//Calculate 60 days ago.
long current_date_long = (new Date()).getTime();
long past_date_long = current_date_long - (1000 * 60 * 60 * 24 * 60);
Date past_date = new Date(past_date_long);
DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
Query.Filter date_filter = new Query.FilterPredicate("DATE_PROPERTY_ON_ENTITY", Query.FilterOperator.LESS_THAN_OR_EQUAL, past_date);
Query date_query = new Query("ENTITY_KIND").setFilter(date_filter);
PreparedQuery date_query_results = datastore.prepare(date_query);
Iterator<Entity> iterate_over_old_entities = date_query_results.asIterator();
while (iterate_over_old_entities.hasNext()) {
Entity old_entity = iterate_over_old_entities.next();
System.out.println("Deleting: " + old_entity.getProperties());
datastore.delete(old_entity.getKey());
}
Note that is a simplified function – it’s useful if you have a handful of entities that need deleting, but if you have more than a handful, you should convert to using datastore cursors and paging through entities to delete.
