如何使用Objectify在Google Cloud Plateform中的多个实体上使用交易？

Question

I have Entity1 and Entity2 , their Manager respectively NewQManager and QAManager and Services QAService and NewQService .
What I want to do : I want to remove Question from Entity1 and add it to Entity2 in a single transaction, for that, I am using Objectify services in AbstractTransaction class which is extended by QAService . However, I am getting the following error:

java.lang.IllegalArgumentException: operating on too many entity groups in a single transaction.

QuestionManager.java

QAService.getInstance().implementTransaction(
        repo -> {
        NewQManager.getInstance().remove(question);
        QAManager.getInstance().addOrUpdateItem(question);
            return true;
        });

QAService.java

public class QAService extends AbstractTransaction {
    public static QAService getInstance() {
        if (instance != null)
            return instance;

        instance = new QAService();
        return instance;
    }
}

AbstractTransaction.java

public class AbstractTransaction<T, ID> {

    public <A> A implementTransaction(Function<AbstractTransaction<T, ID>, A> operations) {
        return ofy().transact(() -> operations.apply(this));
    }

    public T save(T entity) {
        ofy().save().entity(entity).now();
        return entity;
    }
}

Error

    java.lang.IllegalArgumentException: operating on too many entity groups in a single transaction.
        at com.google.appengine.api.datastore.DatastoreApiHelper.translateError(DatastoreApiHelper.java:52)
        at com.google.appengine.api.datastore.DatastoreApiHelper$1.convertException(DatastoreApiHelper.java:135)
        at com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:109)
        at com.google.appengine.api.datastore.Batcher$ReorderingMultiFuture.get(Batcher.java:115)
        at com.google.appengine.api.datastore.FutureHelper$TxnAwareFuture.get(FutureHelper.java:186)
        at com.googlecode.objectify.cache.TriggerFuture.get(TriggerFuture.java:100)
        at com.googlecode.objectify.impl.ResultAdapter.now(ResultAdapter.java:34)
        at com.googlecode.objectify.util.ResultWrapper.translate(ResultWrapper.java:22)
        at com.googlecode.objectify.util.ResultWrapper.translate(ResultWrapper.java:10)
        at com.googlecode.objectify.util.ResultTranslator.nowUncached(ResultTranslator.java:21)
        at com.googlecode.objectify.util.ResultCache.now(ResultCache.java:30)
        at com.googlecode.objectify.util.ResultWrapper.translate(ResultWrapper.java:22)
        at com.googlecode.objectify.util.ResultWrapper.translate(ResultWrapper.java:10)
        at com.googlecode.objectify.util.ResultTranslator.nowUncached(ResultTranslator.java:21)
        at com.googlecode.objectify.util.ResultCache.now(ResultCache.java:30)
com.vivoiz.healofy.backend.commonServices.services.AbstractTransaction.save(AbstractTransaction.java:44)

Answer 1

All this AbstractTransaction stuff looks weird and the extra complexity is probably hiding what you are doing.

One of the fundamental limits of the datastore is you can only enlist 25 entity groups in a single transaction. Somehow you are doing that, possibly by @Load groups - it's impossible to tell from what you've posted.

The solution is "load less stuff in your transaction".