CosmosDB中的NULL连续令牌 [英] NULL Continuation Token in CosmosDB

问题描述

我知道，如果延续令牌为null(整个令牌json为null)，则这意味着下一个请求中将不再有数据.

I know that if the continuation token is null (the whole token json is null), that means there will be no more data in the next request.

就我而言，我检查了下一页中肯定没有更多数据，并且该令牌应该为空.但它会返回此半"空令牌...

In my case, I checked that there is definitely no more data in the next page, and the token is supposed to be null. But it returns this "half" null token...

令牌看起来像这样:

"{\"令牌\:空，\"范围\:{\"最小\:\" xxxxxxxxxx \，\"最大\:\" xxxxxxxxxx \}}""

"{\"token\":null,\"range\":{\"min\":\"xxxxxxxxxx\",\"max\":\"xxxxxxxxxx\"}}"

仅令牌为空，但min和max不为空，这表示什么?换句话说，我应该使用continuation == null还是continuation.token == null来查看下一页是否还有更多数据?

Only the token is null, but min and max are not null, what does it indicate? In another word, should I use continuation == null or continuation.token == null to see whether there is more data in the next page?

推荐答案

对于某些背景上下文:

• Cosmos DB是一个分布式数据库，其中的数据和请求在多个后端服务器之间进行分区(以将存储和吞吐量扩展到单个服务器之外).
• 之所以提出这一点，是因为您可能执行路由到单个分区的查询(通过在查询的WHERE/filter子句中包含分区键)，以及执行跨多个分区散开的查询.
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• 在每个分区的范围内-查询结果以分页方式返回.
• 要了解有关分区的更多信息-请参阅: https://docs.microsoft.com/en-us/azure/cosmos-db/partition-data

• Cosmos DB is a distributed database, in which data and requests are partitioned across multiple backend servers (to scale storage and throughput beyond a single server).
• I bring this up because you may perform queries that are routed to a single partition (by including the partition key in the WHERE / filter clause of your query) - as well as perform queries that fan out across multiple partitions.
• Within the scope of each partition - query results are returned in a paginated manner.
• To learn more about partitioning - see: https://docs.microsoft.com/en-us/azure/cosmos-db/partition-data

您看到的令牌是来自SDK的复合延续令牌，其中包含:

The token you are seeing is a composite continuation token from the SDK that incorporates:

• 来自Cosmos DB后端的信息，以恢复查询执行并检索特定分区上的下一页(令牌字段)
• 后端继续令牌来自哪个分区的信息(范围字段).

您看到的是，对于SDK所查询的特定范围，没有更多结果.

What you are seeing is that for the particular range the SDK is querying there were no more results.

关于SDK为什么不只为延续令牌提供json null值的原因: 该SDK已到达给定分区的末尾，但仍然需要访问其他分区以确保没有更多与您的过滤器匹配的文档/需要返回给客户端.

As for why the SDK does not just give a json null value for the continuation token: The SDK has reached the end for a given partition but mstill needs to visit other partitions to know for sure that there are no more documents that match your filter / need to be returned to the client.

SDK访问完所有分区后，将返回空连续性.

When the SDK is done visiting all partitions it will return a null continuation.

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