将Google Gloud Datastore实体从一个名称空间复制到另一个名称空间

Question

I'm copying Google Cloud Datastore entities from one namespace to an other with java like this:

Key newKey = Key.newBuilder(oldEntity.getKey()).setNamespace(NEW_NAMESPACE).build();
datastore.put(Entity.newBuilder(oldEntity).setKey(newKey).build());

Since the entities have numerid id's generated by Datastore and the id's of the copied entities need to remain the same I need to also let Datastore know to allocate these id's, for that I'm using DatastoreService.allocateIdRange

But this is giving me an error:

Exceeded maximum allocated IDs

Does this mean that there is no way to achieve what I'm trying to achieve?

EDIT 1

The code that allocates the ids:

@POST
public void post(
        @QueryParam("namespace") String namespace,
        @QueryParam("kind") String kind,
        @QueryParam("id") long id,
        @QueryParam("parentKind") String parentKind,
        @QueryParam("parentName") String parentName,
        @QueryParam("parentId") Long parentId
) {
    NamespaceManager.set(namespace);
    DatastoreService ds = DatastoreServiceFactory.getDatastoreService();
    Key parent = null;
    if (parentKind != null) {
        if (parentName != null)
            parent = KeyFactory.createKey(parentKind, parentName);
        else
            parent = KeyFactory.createKey(parentKind, parentId);
    }
    ds.allocateIdRange(new KeyRange(parent, kind, id, id));
}

Answer 1

I think you can skip the key creation. This is my code for updating namespaces:

GoogleCloudDatastore gds = new GoogleCloudDatastore();
Datastore ds = gds.getCredentials();

final KeyFactory keyFactory = ds.newKeyFactory().setKind(entityKind).setNamespace(NAME_SPACE);
Key newKey = ds.allocateId(oldEntity.getKey);
Entity newEntity= Entity.newBuilder(newKey).set("someParameterName", someParameterValue).build();

Hope this helps.

Answer 2

Here is an answer provided on Google's Issue Tracker:

allocateIdRange only works with Sequential contiguous IDs and not Scattered IDs which are above the Sequential ID range.

As explained in the 'Best Practices' documentation, if need be it is recommended to send an 'allocateIds' request to Datastore to find and allocate a contiguous range of unique IDs and use those to save entities to, instead of saving entities to the Datastore first which are auto-assigned Scattered IDs and cannot be allocated with allocateIdRange.