App引擎批量加载器下载警告“__key__没有降序索引，执行序列下载” [英] App engine bulk loader download warning "No descending index on __key__, performing serial download"

问题描述

我使用以下命令下载所有类型的实例：

  appcfg.py download_data --config_file = bulkloader.yaml --kind = ModelName --filename = ModelName.csv --url = http：//appid.appspot.com/remote_api 
  

如果这种类型的实例比批量大，那么我得到这个警告：

  __key__没有降序索引，执行序列化下载
  

我没有任何自定义索引或任何禁用索引的属性。

我需要做些什么来解决这个警告，还是只是一个我可以忽略的警告？它会影响下载的速度吗？

Bulkloader上的这篇文章在示例输出中包含了警告消息，但没有提及它。

这篇文章在应用引擎组上说我需要创建一个索引。然而，添加更多索引会减慢对我的实体的写入 - 我宁愿不这样做，因为我将更频繁地编写实体，而不是进行批量数据下载。

感谢。

解决方案

正如错误所描述的， __ key __ 为您下载的型号，散装加载程序必须连续下载。如果按照所述添加索引，它将能够并行下载。如果你不这样做，它会正常工作，但下载速度会比较慢，因为它是连续运行的。

请注意，额外的索引对延迟只有很小的影响，因为索引行是与实体写入并行写入的，这意味着写入只需要最慢的更新。

I'm using the following to download all instances of one of my kinds:

appcfg.py download_data --config_file=bulkloader.yaml --kind=ModelName --filename=ModelName.csv --url=http://appid.appspot.com/remote_api

If the kind has more instances than the batch size, then I get this warning:

No descending index on __key__, performing serial download

I don't have any custom indexes, or any properties with indexes disabled.

Do I 'need' to do something to resolve this warning, or is it just a warning I can safely ignore? Does it effect the speed of the download?

This article on the bulkloader includes the warning message in the sample output, but makes no mention of it.

This post on the app engine group says that I need to create an index. However adding more indexes would slow down writes to my entities - which I'd rather not do as I am going to be writing entities more often than I will be doing bulk data downloads.

Thanks.

解决方案

As the error describes, without a descending index on __key__ for the model you're downloading, the bulkloader has to download serially. If you add the index as described, it will be able to download in parallel. If you don't, it will work fine, but will be slower to download, as it operates serially.

Note that an additional index has only a small impact on latency, as index rows are written in parallel to the entity write, meaning the write only takes as long as the slowest update.

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