$listSampledQueries

Definition定义

$listSampledQueries

Returns sampled queries for all collections or a specific collection. 返回所有集合或特定集合的采样查询。Sampled queries are used by the analyzeShardKey command to calculate metrics about the read and write distribution of a shard key.analyzeShardKey命令使用采样查询来计算有关分片键的读写分布的度量。

Syntax语法

$listSampledQueries has this syntax:具有以下语法：

{
   $listSampledQueries: { namespace: <namespace> }
}

Behavior行为

• To list sampled queries for a single collection, specify the collection in the namespace argument.若要列出单个集合的采样查询，请在namespace参数中指定集合。
• To list sampled queries for all collections, omit the namespace argument.若要列出所有集合的采样查询，请省略namespace参数。

Access Control访问控制

$listSampledQueries requires the clusterMonitor role on the cluster.需要群集上的clusterMonitor角色。

Limitations局限性

• You cannot use $listSampledQueries on Atlas multitenant configurations.不能在Atlas多租户配置上使用$listSampledQueries。
• You cannot use $listSampledQueries on standalone deployments.不能在独立部署上使用$listSampledQueries。
• You cannot use $listSampledQueries directly against a --shardsvr replica set. When running on a sharded cluster, $listSampledQueries must run against a mongos.不能直接对--shardsvr副本集使用$listSampledQueries。在分片集群上运行时，$listSampledQueries必须针对mongos运行。

Examples实例

db.aggregate( [  { $listSampledQueries: {  } } ] )

db.aggregate( [  { $listSampledQueries: { namespace: "social.post" } } ] )

Output输出

The output fields differ for read and write queries.读查询和写查询的输出字段不同。

{
   _id: <uuid>,
   ns: "<database>.<collection>",
   collectionUuid: <collUUID>,
   cmdName: <find|aggregate|count|distinct>,
   cmd: {
     filter: <object>,
     collation: <object>,
     let: <object>
   },
   expireAt: <date>
}

{
   _id: <uuid>,
   ns: "<database>.<collection>",
   collectionUuid: <collUUID>,
   cmdName: <update|delete|findAndModify>,
   cmd: <object>,
   expireAt: <date>
}