db.collection.stats()¶

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Definition¶

db.collection.stats(scale | options)¶

Returns statistics about the collection. The method includes the following parameters:

Parameter	Type	Description
`scale`	number	Optional. The scale used in the output to display the sizes of items. By default, output displays sizes in `bytes`. To display kilobytes rather than bytes, specify a `scale` value of `1024`. Changed in version 3.0: Legacy parameter format. Mutually exclusive with `options` as a document.
`options`	document	Optional. Alternative to `scale` parameter. Use the `options` document to specify options, including `scale`. New in version 3.0.

The options document can contain the following fields and values:

Field	Type	Description
`scale`	number	Optional. The scale used in the output to display the sizes of items. By default, output displays sizes in bytes. To display kilobytes rather than bytes, specify a `scale` value of `1024`. New in version 3.0.
`indexDetails`	boolean	Optional. If `true`, `db.collection.stats()` returns `index details` in addition to the collection stats. Only works for WiredTiger storage engine. Defaults to `false`. New in version 3.0.
`indexDetailsKey`	document	Optional. If `indexDetails` is `true`, you can use `indexDetailsKey` to filter index details by specifying the index key specification. Only the index that exactly matches `indexDetailsKey` will be returned. If no match is found, `indexDetails` will display statistics for all indexes. Use `getIndexes()` to discover index keys. You cannot use `indexDetailsKey` with `indexDetailsName`. New in version 3.0.
`indexDetailsName`	string	Optional. If `indexDetails` is `true`, you can use `indexDetailsName` to filter index details by specifying the index `name`. Only the index name that exactly matches `indexDetailsName` will be returned. If no match is found, `indexDetails` will display statistics for all indexes. Use `getIndexes()` to discover index names. You cannot use `indexDetailsName` with `indexDetailsField`. New in version 3.0.

Returns:	A document that contains statistics on the specified collection. See `collStats` for a breakdown of the returned statistics.

The db.collection.stats() method provides a wrapper around the database command collStats.

Behavior¶

This method returns a JSON document with statistics related to the current mongod instance. Unless otherwise specified by the key name, values related to size are displayed in bytes and can be overridden by scale.

Note

The scale factor rounds values to whole numbers.

Depending on the storage engine, the data returned may differ. For details on the fields, see output details.

Accuracy after Unexpected Shutdown¶

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.

The amount of drift depends on the number of insert, update, or delete operations performed between the last checkpoint and the unclean shutdown. Checkpoints usually occur every 60 seconds. However, mongod instances running with non-default --syncdelay settings may have more or less frequent checkpoints.

Run validate on each collection on the mongod to to restore the correct statistics after an unclean shutdown.

Index Filter Behavior¶

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.

The indexDetailsKey field takes a document of the following form:

{ '<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.

Unexpected Shutdown and Count¶

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. To restore the correct statistics for the collection, run validate on the collection.

Examples¶

Note

You can find the collection data used for these examples in our Getting Started Guide

Basic Stats Lookup¶

The following operation returns stats on the restaurants collection:

db.restaurants.stats()

The operation returns:

{
    "ns" : "guidebook.restaurants",
   "count" : 25359,
   "size" : 10630398,
   "avgObjSize" : 419,
   "storageSize" : 4104192
   "capped" : false,
   "wiredTiger" : {
         "metadata" : {
            "formatVersion" : 1
         },
         "creationString" : "allocation_size=4KB,app_metadata=(formatVersion=1),block_allocation=best,block_compressor=snappy,cache_resident=0,checksum=on,colgroups=,collator=,columns=,dictionary=0,encryption=(keyid=,name=),exclusive=0,extractor=,format=btree,huffman_key=,huffman_value=,immutable=0,internal_item_max=0,internal_key_max=0,internal_key_truncate=,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=),lsm=(auto_throttle=,bloom=,bloom_bit_count=16,bloom_config=,bloom_hash_count=8,bloom_oldest=0,chunk_count_limit=0,chunk_max=5GB,chunk_size=10MB,merge_max=15,merge_min=0),memory_page_max=10m,os_cache_dirty_max=0,os_cache_max=0,prefix_compression=0,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-2-7253336746667145592",
         "LSM" : {
            "bloom filters in the LSM tree" : 0,
            "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,
            "total size of bloom filters" : 0,
            "sleep for LSM checkpoint throttle" : 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 merge throttle" : 0
         },
         "block-manager" : {
            "file allocation unit size" : 4096,
            "blocks allocated" : 338,
            "checkpoint size" : 4096000,
            "allocations requiring file extension" : 338,
            "blocks freed" : 0,
            "file magic number" : 120897,
            "file major version number" : 1,
            "minor version number" : 0,
            "file bytes available for reuse" : 0,
            "file size in bytes" : 4104192
         },
         "btree" : {
            "btree checkpoint generation" : 15,
            "column-store variable-size deleted values" : 0,
            "column-store fixed-size leaf pages" : 0,
            "column-store internal pages" : 0,
            "column-store variable-size leaf pages" : 0,
            "pages rewritten by compaction" : 0,
            "number of key/value pairs" : 0,
            "fixed-record size" : 0,
            "maximum tree depth" : 3,
            "maximum internal page key size" : 368,
            "maximum internal page size" : 4096,
            "maximum leaf page key size" : 3276,
            "maximum leaf page size" : 32768,
            "maximum leaf page value size" : 67108864,
            "overflow pages" : 0,
            "row-store internal pages" : 0,
            "row-store leaf pages" : 0
         },
         "cache" : {
            "bytes read into cache" : 9309503,
            "bytes written from cache" : 10817368,
            "checkpoint blocked page eviction" : 0,
            "unmodified pages evicted" : 0,
            "page split during eviction deepened the tree" : 0,
            "modified pages evicted" : 1,
            "data source pages selected for eviction unable to be evicted" : 0,
            "hazard pointer blocked page eviction" : 0,
            "internal pages evicted" : 0,
            "pages split during eviction" : 1,
            "in-memory page splits" : 1,
            "overflow values cached in memory" : 0,
            "pages read into cache" : 287,
            "overflow pages read into cache" : 0,
            "pages written from cache" : 337
         },
         "compression" : {
            "raw compression call failed, no additional data available" : 0,
            "raw compression call failed, additional data available" : 0,
            "raw compression call succeeded" : 0,
            "compressed pages read" : 287,
            "compressed pages written" : 333,
            "page written failed to compress" : 0,
            "page written was too small to compress" : 4
         },
         "cursor" : {
            "create calls" : 1,
            "insert calls" : 25359,
            "bulk-loaded cursor-insert calls" : 0,
            "cursor-insert key and value bytes inserted" : 10697901,
            "next calls" : 76085,
            "prev calls" : 1,
            "remove calls" : 0,
            "cursor-remove key bytes removed" : 0,
            "reset calls" : 25959,
            "restarted searches" : 0,
            "search calls" : 0,
            "search near calls" : 594,
            "update calls" : 0,
            "cursor-update value bytes updated" : 0
         },
         "reconciliation" : {
            "dictionary matches" : 0,
            "internal page multi-block writes" : 1,
            "leaf page multi-block writes" : 2,
            "maximum blocks required for a page" : 47,
            "internal-page overflow keys" : 0,
            "leaf-page overflow keys" : 0,
            "overflow values written" : 0,
            "pages deleted" : 0,
            "page checksum matches" : 0,
            "page reconciliation calls" : 4,
            "page reconciliation calls for eviction" : 1,
            "leaf page key bytes discarded using prefix compression" : 0,
            "internal page key bytes discarded using suffix compression" : 333
         },
         "session" : {
            "object compaction" : 0,
            "open cursor count" : 1
         },
         "transaction" : {
            "update conflicts" : 0
         }
      },
      "nindexes" : 4,
      "totalIndexSize" : 626688,
      "indexSizes" : {
         "_id_" : 217088,
         "borough_1_cuisine_1" : 139264,
         "cuisine_1" : 131072,
         "borough_1_address.zipcode_1" : 139264
      },
      "ok" : 1
 }

As stats was not give a scale parameter, all size values are in bytes.

Stats Lookup With Scale¶

The following operation changes the scale of data from bytes to kilobytes by specifying a scale of 1024:

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

The operation returns:

{
   "ns" : "guidebook.restaurants",
   "count" : 25359,
   "size" : 10381,
   "avgObjSize" : 419,
   "storageSize" : 4008,
   "capped" : false,
   "wiredTiger" : {
      ...
   },
   "nindexes" : 4,
   "totalIndexSize" : 612,
   "indexSizes" : {
      "_id_" : 212,
      "borough_1_cuisine_1" : 136,
      "cuisine_1" : 128,
      "borough_1_address.zipcode_1" : 136
   },
   "ok" : 1
}

Statistics Lookup With Index Details¶

The following operation creates an indexDetails document that contains information related to each of the indexes within the collection:

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

The operation returns:

{
   "ns" : "guidebook.restaurants",
   "count" : 25359,
   "size" : 10630398,
   "avgObjSize" : 419,
   "storageSize" : 4104192,
   "capped" : false,
   "wiredTiger" : {
      ...
   },
   "nindexes" : 4,
   "indexDetails" : {
      "_id_" : {
         "metadata" : {
            "formatVersion" : 6,
            "infoObj" : "{ \"v\" : 1, \"key\" : { \"_id\" : 1 }, \"name\" : \"_id_\", \"ns\" : \"blogs.posts\" }"
         },
         "creationString" : "allocation_size=4KB,app_metadata=(formatVersion=6,infoObj={ \"v\" : 1, \"key\" : { \"_id\" : 1 }, \"name\" : \"_id_\", \"ns\" : \"blogs.posts\" }),block_allocation=best,block_compressor=,cache_resident=0,checksum=on,colgroups=,collator=,columns=,dictionary=0,encryption=(keyid=,name=),exclusive=0,extractor=,format=btree,huffman_key=,huffman_value=,immutable=0,internal_item_max=0,internal_key_max=0,internal_key_truncate=,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=),lsm=(auto_throttle=,bloom=,bloom_bit_count=16,bloom_config=,bloom_hash_count=8,bloom_oldest=0,chunk_count_limit=0,chunk_max=5GB,chunk_size=10MB,merge_max=15,merge_min=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=75,type=file,value_format=u",
         "type" : "file",
         "uri" : "statistics:table:index-3-7253336746667145592",
         "LSM" : {
            ...
         },
         "block-manager" : {
            ...
         },
         "btree" : {
            ...
         },
         "cache" : {
            ...
         },
         "compression" : {
            ...
         },
         "cursor" : {
            ...
         },
         "reconciliation" : {
            ...
         },
         "session" : {
            ...
         },
         "transaction" : {
            ...
         }
      },
      "borough_1_cuisine_1" : {
         "metadata" : {
            "formatVersion" : 6,
            "infoObj" : "{ \"v\" : 1, \"key\" : { \"borough\" : 1, \"cuisine\" : 1 }, \"name\" : \"borough_1_cuisine_1\", \"ns\" : \"blogs.posts\" }"
         },
         "creationString" : "allocation_size=4KB,app_metadata=(formatVersion=6,infoObj={ \"v\" : 1, \"key\" : { \"borough\" : 1, \"cuisine\" : 1 }, \"name\" : \"borough_1_cuisine_1\", \"ns\" : \"blogs.posts\" }),block_allocation=best,block_compressor=,cache_resident=0,checksum=on,colgroups=,collator=,columns=,dictionary=0,encryption=(keyid=,name=),exclusive=0,extractor=,format=btree,huffman_key=,huffman_value=,immutable=0,internal_item_max=0,internal_key_max=0,internal_key_truncate=,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=),lsm=(auto_throttle=,bloom=,bloom_bit_count=16,bloom_config=,bloom_hash_count=8,bloom_oldest=0,chunk_count_limit=0,chunk_max=5GB,chunk_size=10MB,merge_max=15,merge_min=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=75,type=file,value_format=u",
         "type" : "file",
         "uri" : "statistics:table:index-4-7253336746667145592",
         "LSM" : {
            ...
         },
         "block-manager" : {
            ...
         },
         "btree" : {
            ...
         },
         "cache" : {
            ...
         },
         "compression" : {
            ...
         },
         "cursor" : {
            ...
         },
         "reconciliation" : {
            ...
         },
         "session" : {
            "object compaction" : 0,
            "open cursor count" : 0
         },
         "transaction" : {
            "update conflicts" : 0
         }
      },
      "cuisine_1" : {
         "metadata" : {
            "formatVersion" : 6,
            "infoObj" : "{ \"v\" : 1, \"key\" : { \"cuisine\" : 1 }, \"name\" : \"cuisine_1\", \"ns\" : \"blogs.posts\" }"
         },
         "creationString" : "allocation_size=4KB,app_metadata=(formatVersion=6,infoObj={ \"v\" : 1, \"key\" : { \"cuisine\" : 1 }, \"name\" : \"cuisine_1\", \"ns\" : \"blogs.posts\" }),block_allocation=best,block_compressor=,cache_resident=0,checksum=on,colgroups=,collator=,columns=,dictionary=0,encryption=(keyid=,name=),exclusive=0,extractor=,format=btree,huffman_key=,huffman_value=,immutable=0,internal_item_max=0,internal_key_max=0,internal_key_truncate=,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=),lsm=(auto_throttle=,bloom=,bloom_bit_count=16,bloom_config=,bloom_hash_count=8,bloom_oldest=0,chunk_count_limit=0,chunk_max=5GB,chunk_size=10MB,merge_max=15,merge_min=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=75,type=file,value_format=u",
         "type" : "file",
         "uri" : "statistics:table:index-5-7253336746667145592",
         "LSM" : {
            ...
         },
         "block-manager" : {
            ...
         },
         "btree" : {
            ...
         },
         "cache" : {
            ...
         },
         "compression" : {
            ...
         },
         "cursor" : {
            ...
         },
         "reconciliation" : {
            ...
         },
         "session" : {
            ...
         },
         "transaction" : {
            ...
         }
      },
      "borough_1_address.zipcode_1" : {
         "metadata" : {
            "formatVersion" : 6,
            "infoObj" : "{ \"v\" : 1, \"key\" : { \"borough\" : 1, \"address.zipcode\" : 1 }, \"name\" : \"borough_1_address.zipcode_1\", \"ns\" : \"blogs.posts\" }"
         },
         "creationString" : "allocation_size=4KB,app_metadata=(formatVersion=6,infoObj={ \"v\" : 1, \"key\" : { \"borough\" : 1, \"address.zipcode\" : 1 }, \"name\" : \"borough_1_address.zipcode_1\", \"ns\" : \"blogs.posts\" }),block_allocation=best,block_compressor=,cache_resident=0,checksum=on,colgroups=,collator=,columns=,dictionary=0,encryption=(keyid=,name=),exclusive=0,extractor=,format=btree,huffman_key=,huffman_value=,immutable=0,internal_item_max=0,internal_key_max=0,internal_key_truncate=,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=),lsm=(auto_throttle=,bloom=,bloom_bit_count=16,bloom_config=,bloom_hash_count=8,bloom_oldest=0,chunk_count_limit=0,chunk_max=5GB,chunk_size=10MB,merge_max=15,merge_min=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=75,type=file,value_format=u",
         "type" : "file",
         "uri" : "statistics:table:index-6-7253336746667145592",
         "LSM" : {
            ...
         },
         "block-manager" : {
            ...
         },
         "btree" : {
            ...
         },
         "cache" : {
            ...
         },
         "compression" : {
            ...
         },
         "cursor" : {
            ...
         },
         "reconciliation" : {
            ...
         },
         "session" : {
            ...
         },
         "transaction" : {
            ...
         }
      }
   },
   "totalIndexSize" : 626688,
   "indexSizes" : {
      "_id_" : 217088,
      "borough_1_cuisine_1" : 139264,
      "cuisine_1" : 131072,
      "borough_1_address.zipcode_1" : 139264
   },
   "ok" : 1
}

Statistics Lookup With Filtered Index Details¶

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. To discover index keys and names for the collection, use db.collection.getIndexes().

Given the following index:

{
   "ns" : "guidebook.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.

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.

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

Both operations will return the same output:

{
   "ns" : "blogs.restaurants",
   "count" : 25359,
   "size" : 10630398,
   "avgObjSize" : 419,
   "storageSize" : 4104192,
   "capped" : false,
   "wiredTiger" : {
      ...
   },
   "nindexes" : 4,
   "indexDetails" : {
      "borough_1_cuisine_1" : {
         "metadata" : {
            "formatVersion" : 6,
            "infoObj" : "{ \"v\" : 1, \"key\" : { \"borough\" : 1, \"cuisine\" : 1 }, \"name\" : \"borough_1_cuisine_1\", \"ns\" : \"blogs.posts\" }"
         },
         "creationString" : "allocation_size=4KB,app_metadata=(formatVersion=6,infoObj={ \"v\" : 1, \"key\" : { \"borough\" : 1, \"cuisine\" : 1 }, \"name\" : \"borough_1_cuisine_1\", \"ns\" : \"blogs.posts\" }),block_allocation=best,block_compressor=,cache_resident=0,checksum=on,colgroups=,collator=,columns=,dictionary=0,encryption=(keyid=,name=),exclusive=0,extractor=,format=btree,huffman_key=,huffman_value=,immutable=0,internal_item_max=0,internal_key_max=0,internal_key_truncate=,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=),lsm=(auto_throttle=,bloom=,bloom_bit_count=16,bloom_config=,bloom_hash_count=8,bloom_oldest=0,chunk_count_limit=0,chunk_max=5GB,chunk_size=10MB,merge_max=15,merge_min=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=75,type=file,value_format=u",
         "type" : "file",
         "uri" : "statistics:table:index-4-7253336746667145592",
         "LSM" : {
            ...
         },
         "block-manager" : {
            ...
         },
         "btree" : {
            ...
         },
         "cache" : {
            ...
         },
         "compression" : {
            ...
         },
         "cursor" : {
            ...
         },
         "reconciliation" : {
            ...
         },
         "session" : {
            ...
         },
         "transaction" : {
            ...
         }
      }
   },
   "totalIndexSize" : 626688,
   "indexSizes" : {
      "_id_" : 217088,
      "borough_1_cuisine_1" : 139264,
      "cuisine_1" : 131072,
      "borough_1_address.zipcode_1" : 139264
   },
   "ok" : 1
}

For explanation of the output, see output details.