db.collection.getShardDistribution() (mongosh method方法)

Definition定义

db.collection.getShardDistribution()

Important

mongosh Method方法

This page documents a mongosh method. This is not the documentation for a language-specific driver, such as Node.js.本页记录了一种mongosh方法。这不是针对特定语言驱动程序（如Node.js）的文档。

For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.有关MongoDB API驱动程序，请参阅特定语言的MongoDB驱动程序文档。

Prints the data distribution statistics for a sharded collection.打印分片集合的数据分布统计信息。

Compatibility兼容性

This method is available in deployments hosted in the following environments:此方法在以下环境中托管的部署中可用：

• MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud：云中MongoDB部署的完全托管服务

• MongoDB Enterprise: The subscription-based, self-managed version of MongoDB：MongoDB的基于订阅的自我管理版本
• MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB：MongoDB的源代码可用、免费使用和自我管理版本

Syntax语法

The getShardDistribution() method has the following form:getShardDistribution()方法具有以下形式：

db.collection.getShardDistribution()

Output输出

Shard shard01 at shard01/localhost:27018
{
  data: '38.14MB',
  docs: 1000003,
  chunks: 2,
  'estimated data per chunk': '19.07B',
  'estimated docs per chunk': 500001
}
---
Shard shard02 at shard02/localhost:27019
{
  data: '38.14B',
  docs: 999999,
  chunks: 3,
  'estimated data per chunk': '12.71B',
  'estimated docs per chunk': 333333
}
---
Totals
{
  data: '76.29B',
  docs: 2000002,
  chunks: 5,
  'Shard shard01': [ '50 % data', '50 % docs in cluster', '40B avg obj size on shard' ],
  'Shard shard02': [ '49.99 % data', '49.99 % docs in cluster', '40B avg obj size on shard' ]
}

Shard shard01 at <host-a>   {
  data: <size-a>,
  docs: <count-a>,
  chunks: <number of chunks-a>,
  'estimated data per chunk': <size-a>/<number of chunks-a>,
  'estimated docs per chunk': <count-a>/<number of chunks-a>
}
---
Shard shard02 at <host-b>
{
  data: <size-b>,
  docs: <count-b>,
  chunks: <number of chunks-b>,
  'estimated data per chunk': <size-b>/<number of chunks-b>,
  'estimated docs per chunk': <count-b>/<number of chunks-b>
}
---
Totals
{
  data: <stats.size>,
  docs: <stats.count>,
  chunks: <calc total chunks>,
  Shard shard01: [ <estDataPercent-a> % data, <estDocPercent-a> % docs in cluster, stats.shards[ <shard-a> ].avgObjSize avg obj size on shard ],
  Shard shard02: [ <estDataPercent-b> % data, <estDocPercent-b> % docs in cluster, stats.shards[ <shard-b> ].avgObjSize avg obj size on shard ]
}

<calc total chunks> = <number of chunks-a> + <number of chunks-b>

<estDataPercent-x> = <size-x>/<stats.size>

<estDocPercent-x> = <count-x>/<stats.count>

Behavior行为

After an unclean shutdown of a mongod using the Wired Tiger storage engine, count and size statistics reported by db.collection.getShardDistribution() may be inaccurate.使用Wired Tiger存储引擎不干净地关闭mongod后，db.collection.getShardDistribution()报告的计数和大小统计数据可能不准确。

The amount of drift depends on the number of insert, update, or delete operations performed between the last checkpoint and the unclean shutdown. 漂移量取决于在最后一个检查点和不干净关闭之间执行的插入、更新或删除操作的数量。Checkpoints usually occur every 60 seconds. However, mongod instances running with non-default --syncdelay settings may have more or less frequent checkpoints.检查点通常每60秒出现一次。然而，使用非默认的--syncdelay设置运行的mongod实例可能或多或少地具有检查点。

Run validate on each collection on the mongod to restore statistics after an unclean shutdown.在mongod上的每个集合上运行validate，以在不干净关闭后恢复统计数据。

After an unclean shutdown:不干净停机后：

• validate updates the count statistic in the collStats output with the latest value.validate使用最新值更新collStats输出中的计数统计。
• Other statistics like the number of documents inserted or removed in the collStats output are estimates.其他统计数据，如collStats输出中插入或删除的文档数量，都是估计值。