Google app engine 从Dataflow api在数据存储中保存长度超过1500字节的字符串时出错

当我试图保存一个很长的字符串时，Dataflow作业抛出此错误消息：属性“myProperty”的值超过1500字节，code=INVALID_参数

遵循Google的示例并保存一个字符串longuer然后保存1500字节时出错

我知道，在使用数据存储API时，我可以通过将属性另存为来保存长度超过1500字节的字符串。但是，在示例文档或类文档中没有其他方法可以表明支持该类型

是否有一种方法可以使用该api保存如此长的字符串，以便将其读取为

完整的错误消息如下所示：

java.lang.RuntimeException: com.google.cloud.dataflow.sdk.util.UserCodeException: java.lang.RuntimeException: com.google.cloud.dataflow.sdk.util.UserCodeException: java.lang.RuntimeException: com.google.cloud.dataflow.sdk.util.UserCodeException: java.lang.RuntimeException: com.google.cloud.dataflow.sdk.util.UserCodeException: com.google.datastore.v1.client.DatastoreException: The value of property "dalekTestExecutions" is longer than 1500 bytes., code=INVALID_ARGUMENT
    at com.google.cloud.dataflow.sdk.runners.worker.SimpleParDoFn$1.output(SimpleParDoFn.java:162)
    at com.google.cloud.dataflow.sdk.util.DoFnRunnerBase$DoFnContext.outputWindowedValue(DoFnRunnerBase.java:288)
    at com.google.cloud.dataflow.sdk.util.DoFnRunnerBase$DoFnContext.outputWindowedValue(DoFnRunnerBase.java:284)
    at com.google.cloud.dataflow.sdk.util.DoFnRunnerBase$DoFnProcessContext$1.outputWindowedValue(DoFnRunnerBase.java:508)
    at com.google.cloud.dataflow.sdk.util.GroupAlsoByWindowsAndCombineDoFn.closeWindow(GroupAlsoByWindowsAndCombineDoFn.java:205)
    at com.google.cloud.dataflow.sdk.util.GroupAlsoByWindowsAndCombineDoFn.processElement(GroupAlsoByWindowsAndCombineDoFn.java:192)
    at com.google.cloud.dataflow.sdk.util.SimpleDoFnRunner.invokeProcessElement(SimpleDoFnRunner.java:49)
    at com.google.cloud.dataflow.sdk.util.DoFnRunnerBase.processElement(DoFnRunnerBase.java:139)
    at com.google.cloud.dataflow.sdk.runners.worker.SimpleParDoFn.processElement(SimpleParDoFn.java:190)
    at com.google.cloud.dataflow.sdk.runners.worker.ForwardingParDoFn.processElement(ForwardingParDoFn.java:42)
    at com.google.cloud.dataflow.sdk.runners.worker.DataflowWorkerLoggingParDoFn.processElement(DataflowWorkerLoggingParDoFn.java:47)
    at com.google.cloud.dataflow.sdk.util.common.worker.ParDoOperation.process(ParDoOperation.java:55)
    at com.google.cloud.dataflow.sdk.util.common.worker.OutputReceiver.process(OutputReceiver.java:52)
    at com.google.cloud.dataflow.sdk.util.common.worker.ReadOperation.runReadLoop(ReadOperation.java:224)
    at com.google.cloud.dataflow.sdk.util.common.worker.ReadOperation.start(ReadOperation.java:185)
    at com.google.cloud.dataflow.sdk.util.common.worker.MapTaskExecutor.execute(MapTaskExecutor.java:72)
    at com.google.cloud.dataflow.sdk.runners.worker.DataflowWorker.executeWork(DataflowWorker.java:287)
    at com.google.cloud.dataflow.sdk.runners.worker.DataflowWorker.doWork(DataflowWorker.java:223)
    at com.google.cloud.dataflow.sdk.runners.worker.DataflowWorker.getAndPerformWork(DataflowWorker.java:173)
    at com.google.cloud.dataflow.sdk.runners.worker.DataflowWorkerHarness$WorkerThread.doWork(DataflowWorkerHarness.java:193)
    at com.google.cloud.dataflow.sdk.runners.worker.DataflowWorkerHarness$WorkerThread.call(DataflowWorkerHarness.java:173)
    at com.google.cloud.dataflow.sdk.runners.worker.DataflowWorkerHarness$WorkerThread.call(DataflowWorkerHarness.java:160)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

---

通过排除索引中的值，可以保存长度超过1500字节的字符串：

Value longString = Value.newBuilder()
    .setStringValue(...)
    .setExcludeFromIndexes(true)
    .build();

如果您需要与App Engine的

com.google.appengine.api.datastore.Text

type兼容，您还需要将含义设置为15：

Value longString = Value.newBuilder()
    .setStringValue(...)
    .setExcludeFromIndexes(true)
    .setMeaning(15)
    .build();

确切地说：

StringValue.newBuilder(yourString).setExcludeFromIndexes(true).build()

---

数据存储为每个属性创建索引，因此属性的默认限制为1500字节。现在，如果需要存储大JSON之类的数据，则可以通过以下方式指定此属性不需要索引：

Entity newEntity =
                Entity.newBuilder(key)
                        .set("time", Timestamp.parseTimestamp("1970-01-01T00:00:00Z"))
                        .set("message", StringValue.newBuilder(JSON).setExcludeFromIndexes(true).build())
                        .build();

---

这样，您将能够保存更大的数据，而不是默认的1500字节限制

请在您的答案中添加更多描述。