$collStats (aggregation stage)（聚合阶段）

latencyStats

If you run $collStats with the latencyStats: {} option on a matrices collection:如果在matrices集合上运行带有latencyStats:{}选项的$collStats：

db.matrices.aggregate( [ { $collStats: { latencyStats: { histograms: true } } } ] )

The query returns a result similar to the following:查询返回类似于以下内容的结果：

{ "ns" : "test.matrices",
  "host" : "mongo.example.net:27017",
  "localTime" : ISODate("2017-10-06T19:43:56.599Z"),
  "latencyStats" :
    { "reads" :
        { "histogram" : [
            { "micros" : Long(16),
              "count" : Long(3) },
            { "micros" : Long(32),
              "count" : Long(1) },
            { "micros" : Long(128),
              "count" : Long(1) } ],
          "latency" : Long(264),
          "ops" : Long(5) },
      "writes" :
        { "histogram" : [
            { "micros" : Long(32),
              "count" : Long(1) },
            { "micros" : Long(64),
              "count" : Long(3) },
            { "micros" : Long(24576),
              "count" : Long(1) } ],
          "latency" : Long(27659),
          "ops" : Long(5) },
      "commands" :
        { "histogram" : [
            {
                "micros" : Long(196608),
                "count" : Long(1)
            }
          ],
          "latency" : Long(0),
          "ops" : Long(0) },
      "transactions" : {
          "histogram" : [ ],
          "latency" : Long(0),
          "ops" : Long(0)
      }
    }
}

storageStats

If you run $collStats with the storageStats: {} option on a matrices collection using the WiredTiger Storage Engine:如果使用WiredTiger存储引擎在matrices集合上运行带有storageStats:{}选项的$collStats：

db.matrices.aggregate( [ { $collStats: { storageStats: { } } } ] )

The query returns a result similar to the following:查询返回类似于以下内容的结果：

  {
    localTime : 2020-03-06T01:44:57.437Z,
    storageStats: {
    size: 608500363,
    count: 1104369,
    avgObjectSize: 550,
    storageSize: 4096,
    freeStorageSize: 2490380,
    capped: false,
    wiredTiger : {
      ...
    },
    nindexes : 2,
    indexDetails : {
      ...
    },
    indexBuilds: [
      _id_1_abc_1
    ],
    totalIndexSize: 260337664,
    indexSizes: {
    _id_ : 9891840,
    _id_1_abc_1 : 250445824
    },
    totalSize: 613216256,
    scaleFactor : 1
  },
  host : 'mongo.example.net:27017',
  ns : 'test.matrices'
}

db.weather.aggregate( [ { $collStats: { storageStats: { } } } ] ).toArray()[0].storageStats.timeseries

{
   bucketsNs: 'test.weather',
   bucketCount: 12,
   avgBucketSize: 300,
   numActiveBuckets: 1,
   numBucketInserts: 12,
   numBucketUpdates: 0,
   numBucketsOpenedDueToMetadata: 1,
   numBucketsClosedDueToCount: 0,
   numBucketsClosedDueToSchemaChange: 0,
   numBucketsClosedDueToSize: 0,
   numBucketsClosedDueToTimeForward: 11,
   numBucketsClosedDueToMemoryThreshold: 0,
   numCommits: 12,
   numMeasurementsGroupCommitted: 0,
   numWaits: 0,
   numMeasurementsCommitted: 12,
   avgNumMeasurementsPerCommit: 1,
   numBucketsClosedDueToReopening: 0,
   numBucketsArchivedDueToMemoryThreshold: 0,
   numBucketsArchivedDueToTimeBackward: 0,
   numBucketsReopened: 0,
   numBucketsKeptOpenDueToLargeMeasurements: 0,
   numBucketsClosedDueToCachePressure: 0,
   numBucketsFrozen: 0,
   numCompressedBucketsConvertedToUnsorted: 0,
   numBucketsFetched: 0,
   numBucketsQueried: 0,
   numBucketFetchesFailed: 0,
   numBucketQueriesFailed: 1,
   numBucketReopeningsFailed: 0,
   numDuplicateBucketsReopened: 0
}

count

If you run $collStats with the count: {} option on a matrices collection:如果在matrices集合上运行带有count:{}选项的$collStats：

db.matrices.aggregate( [ { $collStats: { count: { } } } ] )

The query returns a result similar to the following:查询返回类似于以下内容的结果：

{
  "ns" : "test.matrices",
  "host" : "mongo.example.net:27017",
  "localTime" : ISODate("2017-10-06T19:43:56.599Z"),
  "count" : 1103869
}

queryExecStats

If you run $collStats with the queryExecStats: {} option on a matrices collection:如果在matrices集合上使用queryExecStats:{}选项运行$collStats：

db.matrices.aggregate( [ { $collStats: { queryExecStats: { } } } ] )

The query returns a result similar to the following:查询返回类似于以下内容的结果：

{
  "ns": "test.matrices",
  "host": "mongo.example.net:27017",
  "localTime": ISODate("2020-06-03T14:23:29.711Z"),
  "queryExecStats": {
      "collectionScans": {
          "total": Long(33),
          "nonTailable": Long(31)
      }
  }
}

$collStats on Sharded Collections分片集合上的$collStats

$collStats outputs one document per shard when run on sharded collections. Each output document contains a shard field with the name of the shard the document corresponds to.$collStats在分片集合上运行时，每个分片输出一个文档。每个输出文档都包含一个shard字段，其中包含文档对应的分片的名称。

For example, if you run $collStats on a sharded collection with the count: {} option on a collection named matrices:例如，如果在名为matrices的集合上使用count: {}选项对分片集合运行$collStats：

db.matrices.aggregate( [ { $collStats: { count: { } } } ] )

The query returns a result similar to the following:查询返回类似于以下内容的结果：

{
  "ns" : "test.matrices",
  "shard" : "s1",
  "host" : "s1-mongo1.example.net:27017",
  "localTime" : ISODate("2017-10-06T15:14:21.258Z"),
  "count" : 661705
}
{
  "ns" : "test.matrices",
  "shard" : "s2",
  "host" : "s2-mongo1.example.net:27017",
  "localTime" : ISODate("2017-10-06T15:14:21.258Z"),
  "count" : 442164
}

latencyStats

The following example creates and runs a $collStats pipeline stage with the latencyStats option:以下示例创建并运行具有latencyStats选项的$collStats管道阶段：

const pipeline = [
  {
    $collStats: {
      latencyStats: {histograms: true}
    }
  }
];

const cursor = collection.aggregate(pipeline);  
return cursor;

storageStats

The following example creates and runs a $collStats pipeline stage with the storageStats option:以下示例创建并运行一个带有storageStats选项的$collStats管道阶段：

const pipeline = [{ $collStats: { storageStats: {} } }]; 

const cursor = collection.aggregate(pipeline);
return cursor;

const pipeline = [{ $collStats: { storageStats: {} } }];

const cursor = collection.aggregate(pipeline);
const timeSeriesStats = resultsTimeSeries[0].storageStats.timeseries;  

return timeSeriesStats;

count

The following example runs a $collStats pipeline stage with the count option on a collection:以下示例在集合上运行一个带有count选项的$collStats管道阶段：

const pipeline = [{ $collStats: { count: {} } }]; 

const cursor =  collection.aggregate(pipeline);
return cursor;

queryExecStats

The following example creates and runs a $collStats pipeline stage with the queryExecStats option:以下示例创建并运行一个带有queryExecStats选项的$collStats管道阶段：

const pipeline = [{ $collStats: { queryExecStats: {} } }]; 

const cursor =  collection.aggregate(pipeline);
return cursor;