Google Cloud Datastore - get after insert in one request

Question

I am trying to retrieve an entity immediately after it was saved. When debugging, I insert the entity, and check entities in google cloud console, I see it was created.

Key key = datastore.put(fullEntity)

After that, I continue with getting the entity with

datastore.get(key)

, but nothing is returned. How do I retrieve the saved entity within one request?

I've read this question Missing entities after insertion in Google Cloud DataStore but I am only saving 1 entity, not tens of thousands like in that question

I am using Java 11 and google datastore (com.google.cloud.datastore. package)*

edit: added code how entity was created

public Key create.... {
    // creating the entity inside a method
    Transaction txn = this.datastore.newTransaction();

    this.datastore = DatastoreOptions.getDefaultInstance().getService();
    Builder<IncompleteKey> builder = newBuilder(entitykey);

    setLongOrNull(builder, "price", purchase.getPrice());
    setTimestampOrNull(builder, "validFrom", of(purchase.getValidFrom()));
    setStringOrNull(builder, "invoiceNumber", purchase.getInvoiceNumber());
    setBooleanOrNull(builder, "paidByCard", purchase.getPaidByCard());

    newPurchase = entityToObject(this.datastore.put(builder.build()));
    if (newPurchase != null && purchase.getItems() != null && purchase.getItems().size() > 0) {
        for (Item item : purchase.getItems()) {
            newPurchase.getItems().add(this.itemDao.save(item, newPurchase));
        }
    }
    txn.commit();
    return newPurchase.getKey();
}

after that, I am trying to retrieve the created entity

Key key = create(...);
Entity e = datastore.get(key)

Answer 1

I believe that there are a few issues with your code, but since we are unable to see the logic behind many of your methods, here comes my guess.

First of all, as you can see on the documentation, it's possible to save and retrieve an entity on the same code, so this is not a problem.

It seems like you are using a transaction which is right to perform multiple operations in a single action, but it doesn't seem like you are using it properly. This is because you only instantiate it and close it, but you don't put any operation on it. Furthermore, you are using this.datastore to save to the database, which completely neglects the transaction.

So you either save the object when it has all of its items already added or you create a transaction to save all the entities at once.

And I believe you should use the entityKey in order to fetch the added purchase afterwards, but don't mix it.

Also you are creating the Transaction object from this.datastore before instantiating the latter, but I assume this is a copy-paste error.