db.collection.stats()

Scaled Sizes缩放尺寸

Unless otherwise specified by the metric name (such as "bytes currently in the cache"), values related to size are displayed in bytes and can be overridden by scale.除非度量名称另有规定（例如"bytes currently in the cache"），否则与大小相关的值以字节为单位显示，并且可以按比例覆盖。

The scale factor rounds the affected size values to whole numbers.比例因子将受影响的大小值四舍五入为整数。

Storage Engine存储引擎

Depending on the storage engine, the data returned may differ. 根据存储引擎的不同，返回的数据可能有所不同。For details on the fields, see output details.有关字段的详细信息，请参阅输出详细信息。

Accuracy after Unexpected Shutdown意外停机后的准确性

After an unclean shutdown of a mongod using the Wired Tiger storage engine, count and size statistics reported by db.collection.stats() may be inaccurate.在使用Wired Tiger存储引擎不干净地关闭mongod之后，db.collection.stats()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非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. 检查点通常每60秒出现一次。However, mongod instances running with non-default --syncdelay settings may have more or less frequent checkpoints.然而，使用非默--syncdelay设置运行的mongod实例可能或多或少有频繁的检查点。

Run validate on each collection on the mongod to restore statistics after an unclean shutdown.对mongod上的每个集合运行validate，以在不干净的关闭后恢复统计信息。

After an unclean shutdown:不干净关机后：

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

Replica Set Member State Restriction副本集成员状态限制

Starting in MongoDB 4.4, to run on a replica set member, collStats operations require the member to be in PRIMARY or SECONDARY state. 从MongoDB 4.4开始，要在副本集成员上运行，collStats操作要求该成员处于PRIMARY或SECONDARY状态。If the member is in another state, such as STARTUP2, the operation errors.如果成员处于其他状态，例如STARTUP2，则操作将出错。

In previous versions, the operations also run when the member is in STARTUP2. The operations wait until the member transitioned to RECOVERING.在以前的版本中，成员处于STARTUP2时也会运行这些操作。操作将等待，直到成员转换到RECOVERING。

Index Filter Behavior索引筛选器行为

Filtering on indexDetails using either indexDetailsKey or indexDetailsName will only return a single matching index. If no exact match is found, indexDetails will show information on all indexes for the collection.使用indexDetailsKey或indexDetailsName筛选indexDetails将只返回一个匹配的索引。如果找不到完全匹配，indexDetails将显示有关集合的所有索引的信息。

The indexDetailsKey field takes a document of the following form:indexDetailsKey字段采用以下形式的文档：

{ '<string>' : <value>, '<string>' : <value>, ... }

Where <string> is the field that is indexed and <value> is either the direction of the index, or the special index type such as text or 2dsphere. See index types for the full list of index types.其中<string>是被索引的字段，<value>是索引的方向，或者是特殊的索引类型，如text或2dsphere。有关索引类型的完整列表，请参阅索引类型。

Unexpected Shutdown and Count意外关闭和计数

For MongoDB instances using the WiredTiger storage engine, after an unclean shutdown, statistics on size and count may off by up to 1000 documents as reported by collStats, dbStats, count. 对于使用WiredTiger存储引擎的MongoDB实例，在不干净的关闭后，collStats、dbStats、count报告的大小和计数统计数据可能会减少多达1000个文档。To restore the correct statistics for the collection, run validate on the collection.若要恢复集合的正确统计信息，请对集合运行validate。

In-Progress Indexes进行中索引

Starting in MongoDB 4.2, the db.collection.stats() includes information on indexes currently being built. 从MongoDB 4.2开始，db.collection.stats()包含当前正在构建的索引的信息。For details, see:有关详细信息，请参阅：

• collStats.nindexes
• collStats.indexDetails
• collStats.indexBuilds
• collStats.totalIndexSize
• collStats.indexSizes

Basic Stats Lookup基本统计信息查找

The following operation returns stats on the restaurants collection in the test database:以下操作返回test数据库中restaurants集合的统计信息：

db.restaurants.stats()

The operation returns:操作返回：

{
   "ns" : "test.restaurants",
   "size" : 7557340,
   "count" : 25359,
   "avgObjSize" : 298,
   "storageSize" : 9670656,
   "freeStorageSize" : 6660096,
   "capped" : false,
   "wiredTiger" : {
         "metadata" : {
            "formatVersion" : 1
         },
         "creationString" : "access_pattern_hint=none,allocation_size=4KB,app_metadata=(formatVersion=1),assert=(commit_timestamp=none,durable_timestamp=none,read_timestamp=none),block_allocation=best,block_compressor=snappy,cache_resident=false,checksum=on,colgroups=,collator=,columns=,dictionary=0,encryption=(keyid=,name=),exclusive=false,extractor=,format=btree,huffman_key=,huffman_value=,ignore_in_memory_cache_size=false,immutable=false,internal_item_max=0,internal_key_max=0,internal_key_truncate=true,internal_page_max=4KB,key_format=q,key_gap=10,leaf_item_max=0,leaf_key_max=0,leaf_page_max=32KB,leaf_value_max=64MB,log=(enabled=true),lsm=(auto_throttle=true,bloom=true,bloom_bit_count=16,bloom_config=,bloom_hash_count=8,bloom_oldest=false,chunk_count_limit=0,chunk_max=5GB,chunk_size=10MB,merge_custom=(prefix=,start_generation=0,suffix=),merge_max=15,merge_min=0),memory_page_image_max=0,memory_page_max=10m,os_cache_dirty_max=0,os_cache_max=0,prefix_compression=false,prefix_compression_min=4,source=,split_deepen_min_child=0,split_deepen_per_child=0,split_pct=90,type=file,value_format=u",
         "type" : "file",
         "uri" : "statistics:table:collection-43-6797839137631957852",
         "LSM" : {
            "bloom filter false positives" : 0,
            "bloom filter hits" : 0,
            "bloom filter misses" : 0,
            "bloom filter pages evicted from cache" : 0,
            "bloom filter pages read into cache" : 0,
            "bloom filters in the LSM tree" : 0,
            "chunks in the LSM tree" : 0,
            "highest merge generation in the LSM tree" : 0,
            "queries that could have benefited from a Bloom filter that did not exist" : 0,
            "sleep for LSM checkpoint throttle" : 0,
            "sleep for LSM merge throttle" : 0,
            "total size of bloom filters" : 0
         },
         "block-manager" : {
            "allocations requiring file extension" : 460,
            "blocks allocated" : 556,
            "blocks freed" : 420,
            "checkpoint size" : 2994176,
            "file allocation unit size" : 4096,
            "file bytes available for reuse" : 6660096,
            "file magic number" : 120897,
            "file major version number" : 1,
            "file size in bytes" : 9670656,
            "minor version number" : 0
         },
         "btree" : {
            "btree checkpoint generation" : 58,
            "column-store fixed-size leaf pages" : 0,
            "column-store internal pages" : 0,
            "column-store variable-size RLE encoded values" : 0,
            "column-store variable-size deleted values" : 0,
            "column-store variable-size leaf pages" : 0,
            "fixed-record size" : 0,
            "maximum internal page key size" : 368,
            "maximum internal page size" : 4096,
            "maximum leaf page key size" : 2867,
            "maximum leaf page size" : 32768,
            "maximum leaf page value size" : 67108864,
            "maximum tree depth" : 3,
            "number of key/value pairs" : 0,
            "overflow pages" : 0,
            "pages rewritten by compaction" : 0,
            "row-store empty values" : 0,
            "row-store internal pages" : 0,
            "row-store leaf pages" : 0
         },
         "cache" : {
            "bytes currently in the cache" : 19401033,
            "bytes dirty in the cache cumulative" : 28415209,
            "bytes read into cache" : 0,
            "bytes written from cache" : 31893695,
            "checkpoint blocked page eviction" : 0,
            "data source pages selected for eviction unable to be evicted" : 0,
            "eviction walk passes of a file" : 0,
            "eviction walk target pages histogram - 0-9" : 0,
            "eviction walk target pages histogram - 10-31" : 0,
            "eviction walk target pages histogram - 128 and higher" : 0,
            "eviction walk target pages histogram - 32-63" : 0,
            "eviction walk target pages histogram - 64-128" : 0,
            "eviction walks abandoned" : 0,
            "eviction walks gave up because they restarted their walk twice" : 0,
            "eviction walks gave up because they saw too many pages and found no candidates" : 0,
            "eviction walks gave up because they saw too many pages and found too few candidates" : 0,
            "eviction walks reached end of tree" : 0,
            "eviction walks started from root of tree" : 0,
            "eviction walks started from saved location in tree" : 0,
            "hazard pointer blocked page eviction" : 0,
            "in-memory page passed criteria to be split" : 4,
            "in-memory page splits" : 2,
            "internal pages evicted" : 0,
            "internal pages split during eviction" : 0,
            "leaf pages split during eviction" : 2,
            "modified pages evicted" : 2,
            "overflow pages read into cache" : 0,
            "page split during eviction deepened the tree" : 0,
            "page written requiring cache overflow records" : 0,
            "pages read into cache" : 0,
            "pages read into cache after truncate" : 1,
            "pages read into cache after truncate in prepare state" : 0,
            "pages read into cache requiring cache overflow entries" : 0,
            "pages requested from the cache" : 76607,
            "pages seen by eviction walk" : 0,
            "pages written from cache" : 552,
            "pages written requiring in-memory restoration" : 0,
            "tracked dirty bytes in the cache" : 0,
            "unmodified pages evicted" : 0
         },
         "cache_walk" : {
            "Average difference between current eviction generation when the page was last considered" : 0,
            "Average on-disk page image size seen" : 0,
            "Average time in cache for pages that have been visited by the eviction server" : 0,
            "Average time in cache for pages that have not been visited by the eviction server" : 0,
            "Clean pages currently in cache" : 0,
            "Current eviction generation" : 0,
            "Dirty pages currently in cache" : 0,
            "Entries in the root page" : 0,
            "Internal pages currently in cache" : 0,
            "Leaf pages currently in cache" : 0,
            "Maximum difference between current eviction generation when the page was last considered" : 0,
            "Maximum page size seen" : 0,
            "Minimum on-disk page image size seen" : 0,
            "Number of pages never visited by eviction server" : 0,
            "On-disk page image sizes smaller than a single allocation unit" : 0,
            "Pages created in memory and never written" : 0,
            "Pages currently queued for eviction" : 0,
            "Pages that could not be queued for eviction" : 0,
            "Refs skipped during cache traversal" : 0,
            "Size of the root page" : 0,
            "Total number of pages currently in cache" : 0
         },
         "compression" : {
            "compressed page maximum internal page size prior to compression" : 4096,
            "compressed page maximum leaf page size prior to compression " : 111392,
            "compressed pages read" : 0,
            "compressed pages written" : 548,
            "page written failed to compress" : 0,
            "page written was too small to compress" : 4
         },
         "cursor" : {
            "bulk loaded cursor insert calls" : 0,
            "cache cursors reuse count" : 74,
            "close calls that result in cache" : 0,
            "create calls" : 4,
            "insert calls" : 50718,
            "insert key and value bytes" : 24500283,
            "modify" : 0,
            "modify key and value bytes affected" : 0,
            "modify value bytes modified" : 0,
            "next calls" : 101747,
            "open cursor count" : 0,
            "operation restarted" : 0,
            "prev calls" : 1,
            "remove calls" : 0,
            "remove key bytes removed" : 0,
            "reserve calls" : 0,
            "reset calls" : 51000,
            "search calls" : 25359,
            "search near calls" : 25485,
            "truncate calls" : 0,
            "update calls" : 0,
            "update key and value bytes" : 0,
            "update value size change" : 0
         },
         "reconciliation" : {
            "dictionary matches" : 0,
            "fast-path pages deleted" : 0,
            "internal page key bytes discarded using suffix compression" : 1077,
            "internal page multi-block writes" : 1,
            "internal-page overflow keys" : 0,
            "leaf page key bytes discarded using prefix compression" : 0,
            "leaf page multi-block writes" : 12,
            "leaf-page overflow keys" : 0,
            "maximum blocks required for a page" : 1,
            "overflow values written" : 0,
            "page checksum matches" : 0,
            "page reconciliation calls" : 80,
            "page reconciliation calls for eviction" : 2,
            "pages deleted" : 0
         },
         "session" : {
            "object compaction" : 0
         },
         "transaction" : {
            "update conflicts" : 0
         }
   },
   "nindexes" : 4,
   "indexBuilds" : [ ],       // Available starting in MongoDB 4.2
   "totalIndexSize" : 704512,
   "totalSize" : 10375168,    // Available starting in MongoDB 4.4
   "indexSizes" : {
      "_id_" : 241664,
      "cuisine_1" : 147456,
      "borough_1_cuisine_1" : 159744,
      "borough_1_address.zipcode_1" : 155648
   },
   "scaleFactor" : 1,        // Available starting in MongoDB 4.2
   "ok" : 1
}

As stats was not give a scale parameter, all size values are in bytes.由于stats没有给出缩放参数，所以所有大小值都以bytes为单位。

Stats Lookup With Scale按比例查找统计信息

The following operation changes the scale of data from bytes to kilobytes by specifying a scale of 1024:以下操作通过指定scale为1024将数据的小数位数从bytes更改为kilobytes：

db.restaurants.stats( { scale : 1024 } )

The operation returns:操作返回：

{
   "ns" : "test.restaurants",
   "size" : 7380,
   "count" : 25359,
   "avgObjSize" : 298,
   "storageSize" : 9444,
   "freeStorageSize" : 6504,
   "capped" : false,
   "wiredTiger" : {
      ...
   },
   "nindexes" : 4,
   "indexBuilds" : [ ],      // Available starting in MongoDB 4.2
   "totalIndexSize" : 688,
   "totalSize" : 10132,      // Available starting in MongoDB 4.4
   "indexSizes" : {
      "_id_" : 236,
      "cuisine_1" : 144,
      "borough_1_cuisine_1" : 156,
      "borough_1_address.zipcode_1" : 152
   },
   "scaleFactor" : 1024,     // Available starting in MongoDB 4.2
   "ok" : 1
}

Statistics Lookup With Index Details具有索引详细信息的统计信息查找

The following operation creates an indexDetails document that contains information related to each of the indexes within the collection:以下操作创建一个indexDetails文档，该文档包含与集合中的每个索引相关的信息：

db.restaurants.stats( { indexDetails : true } )

The operation returns:操作返回：

{
   "ns" : "test.restaurants",
   "size" : 7557340,
   "count" : 25359,
   "avgObjSize" : 298,
   "storageSize" : 9670656,
   "freeStorageSize" : 6660096,
   "capped" : false,
   "wiredTiger" : {
   ...
   },
   "nindexes" : 4,
   "indexDetails" : {
      "_id_" : {
         "metadata" : {
            "formatVersion" : 8
         },
         "creationString" : "access_pattern_hint=none,allocation_size=4KB,app_metadata=(formatVersion=8),assert=(commit_timestamp=none,durable_timestamp=none,read_timestamp=none),block_allocation=best,block_compressor=,cache_resident=false,checksum=on,colgroups=,collator=,columns=,dictionary=0,encryption=(keyid=,name=),exclusive=false,extractor=,format=btree,huffman_key=,huffman_value=,ignore_in_memory_cache_size=false,immutable=false,internal_item_max=0,internal_key_max=0,internal_key_truncate=true,internal_page_max=16k,key_format=u,key_gap=10,leaf_item_max=0,leaf_key_max=0,leaf_page_max=16k,leaf_value_max=0,log=(enabled=true),lsm=(auto_throttle=true,bloom=true,bloom_bit_count=16,bloom_config=,bloom_hash_count=8,bloom_oldest=false,chunk_count_limit=0,chunk_max=5GB,chunk_size=10MB,merge_custom=(prefix=,start_generation=0,suffix=),merge_max=15,merge_min=0),memory_page_image_max=0,memory_page_max=5MB,os_cache_dirty_max=0,os_cache_max=0,prefix_compression=true,prefix_compression_min=4,source=,split_deepen_min_child=0,split_deepen_per_child=0,split_pct=90,type=file,value_format=u",
         "type" : "file",
         "uri" : "statistics:table:index-44-6797839137631957852",
         "LSM" : {
         ...
         },
         "block-manager" : {
         ...
         },
         "btree" : {
         ...
         },
         "cache" : {
         ...
         },
         "cache_walk" : {
         ...
         },
         "compression" : {
         ...
         },
         "cursor" : {
         ...
         },
         "reconciliation" : {
         ...
         },
         "session" : {
         ...
         },
         "transaction" : {
         ...
         }
      },
      "cuisine_1" : {
         ...
      },
      "borough_1_cuisine_1" : {
         ...
      },
      "borough_1_address.zipcode_1" : {
         ...
   },
   "indexBuilds" : [ ],         // Available starting in MongoDB 4.2
   "totalIndexSize" : 704512,
   "totalSize" : 10375168,      // Available starting in MongoDB 4.4
   "indexSizes" : {
      "_id_" : 241664,
      "cuisine_1" : 147456,
      "borough_1_cuisine_1" : 159744,
      "borough_1_address.zipcode_1" : 155648
   },
   "scaleFactor" : 1,          // Available starting in MongoDB 4.2
   "ok" : 1
}

Statistics Lookup With Filtered Index Details具有筛选索引详细信息的统计信息查找

To filter the indexes in the indexDetails field, you can either specify the index keys using the indexDetailsKey option or specify the index name using the indexDetailsName. 要筛选indexDetails字段中的索引，可以使用indexDetailsKey选项指定索引键，也可以使用indexDetailsName指定索引名称。To discover index keys and names for the collection, use db.collection.getIndexes().要发现集合的索引键和名称，请使用db.collection.getIndexes()。

Given the following index:给定以下指数：

{
   "ns" : "test.restaurants",
   "v" : 1,
   "key" : {
      "borough" : 1,
      "cuisine" : 1
   },
   "name" : "borough_1_cuisine_1"
}

The following operation filters the indexDetails document to a single index as defined by the indexDetailsKey document.以下操作将indexDetails文档筛选为indexDetailsKey文档定义的单个索引。

db.restaurants.stats(
   {
      'indexDetails' : true,
      'indexDetailsKey' :
      {
         'borough' : 1,
         'cuisine' : 1
      }
   }
)

The following operation filters the indexDetails document to a single index as defined by the indexDetailsName document.以下操作将indexDetails文档筛选为indexDetailsName文档定义的单个索引。

db.restaurants.stats(
   {
      'indexDetails' : true,
      'indexDetailsName' : 'borough_1_cuisine_1'
   }
)

Both operations will return the same output:两个操作都将返回相同的输出：

{
   "ns" : "test.restaurants",
   "size" : 7557340,
   "count" : 25359,
   "avgObjSize" : 298,
   "storageSize" : 9670656,
   "freeStorageSize" : 6660096,
   "capped" : false,
   "wiredTiger" : {
      ...
   },
   "nindexes" : 4,
   "indexDetails" : {
      "borough_1_cuisine_1" : {
         "metadata" : {
            "formatVersion" : 8
         },
         "LSM" : {
            ...
         },
         "block-manager" : {
            ...
         },
         "btree" : {
            ...
         },
         "cache" : {
            ...
         },
         "cache_walk" : {
            ...
         },
         "compression" : {
            ...
         },
         "cursor" : {
            ...
         },
         "reconciliation" : {
            ...
         },
         "session" : {
            ...
         },
         "transaction" : {
            ...
         }
      }
   },
   "indexBuilds" : [ ],          // Available starting in MongoDB 4.2
   "totalIndexSize" : 704512,
   "totalSize" : 10375168,       // Available starting in MongoDB 4.4
   "indexSizes" : {
      "_id_" : 241664,
      "cuisine_1" : 147456,
      "borough_1_cuisine_1" : 159744,
      "borough_1_address.zipcode_1" : 155648
   },
   "scaleFactor" : 1,            // Available starting in MongoDB 4.2
   "ok" : 1
}

For explanation of the output, see output details.有关输出的说明，请参阅输出详细信息。