How to get Datastore entity id from com.google.datastore.v1.Entity

Question

I have written a code to fetch data from Google Datastore in my Google Cloud Dataflow program. I am able to fetch all fields of the entity except Id field which is autogenerated field. I have tried to use entity.getKey() but I am getting null.

Below is my code snippet,

Datastore datastore = DataflowDatastoreService.getDatastoreObject(null, null, null);
Query.Builder queryBuilder = Query.newBuilder();
Filter filter1 = Filter.newBuilder()
.setPropertyFilter(PropertyFilter.newBuilder()  .setProperty(PropertyReference.newBuilder().setName("cId"))
.setOp(PropertyFilter.Operator.EQUAL)
.setValue(Value.newBuilder().setIntegerValue(1059438885900008L).build()).build()).build();

Filter filter2 = Filter.newBuilder()
.setPropertyFilter(PropertyFilter.newBuilder()
.setProperty(PropertyReference.newBuilder().setName("active"))
.setOp(PropertyFilter.Operator.EQUAL)
.setValue(Value.newBuilder().setBooleanValue(Boolean.TRUE).build()).build()).build();

Filter composeFilter = Filter.newBuilder().setCompositeFilter(CompositeFilter.newBuilder()
                    .addFilters(filter1).setOp(Operator.AND).addFilters(filter2).build()).build();
            queryBuilder.addKind(KindExpression.newBuilder().setName("MyMaster").build());
            queryBuilder.setFilter(composeFilter).build();

RunQueryRequest request = DataflowDatastoreService.makeRequest(queryBuilder.build(), null);
RunQueryResponse response = datastore.runQuery(request);
QueryResultBatch batch = response.getBatch();
List<EntityResult> entityResutls =  batch.getEntityResultsList();
List<Entity> myEntities = new ArrayList<>();

Map<String, Value> entityMap = myEntities(0).getPropertiesMap();

In my code I am able to get all fields in entityMap key but I am not getting key, is there any other way through which I can fetch all the fields with Id.

Answer 1

Note: I'm not a java user, answer based on python experience

Indeed, entities returned in a regular query result do not contain the entity key/ID. Attempting to obtain that from the entity is rather inefficient - you need to reach to the datastore for each individual entity (not even looking at why that doesn't appear to be working for you).

If I need the entity keys/IDs I'd instead use keys-only queries - obtaining the keys, from which I can easily get:

• the key IDs, locally, without making actual datastore calls (in python via key.id(), I don't know the java equivalent)
• the entities via direct key lookup, which can be batched for efficiency.