db.collection.stats()
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MongoDB with drivers
This page documents a mongosh method. To see the equivalent
method in a MongoDB driver, see the corresponding page for your
programming language:
Definition
Use the $collStats aggregation stage instead
of the collStats command and its
mongosh helper method db.collection.stats().
db.collection.stats(<option>)Important
mongosh Method
This page documents a
mongoshmethod. This is not the documentation for database commands or language-specific drivers, such as Node.js.For the database command, see the
collStatscommand.For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.
Returns statistics about the collection.
The method has the following format:
db.collection.stats({ scale: <num>, // Optional indexDetails: <boolean>, // Optional indexDetailsKey: <document>, // Optional indexDetailsName: <string>. // Optional }) FieldTypeDescriptionscalenumberOptional. The scale factor for the various size data. The
scaledefaults to 1 to return size data in bytes. To display kilobytes rather than bytes, specify ascalevalue of1024.If you specify a non-integer scale factor, MongoDB uses the integer part of the specified factor. For example, if you specify a scale factor of
1023.999, MongoDB uses1023as the scale factor.Starting in version 4.2, the output includes the
scaleFactorused to scale the size values.indexDetailsbooleanOptional. If
true,db.collection.stats()returnsindex detailsin addition to the collection stats.Only works for WiredTiger storage engine.
Defaults to
false.indexDetailsKeydocumentOptional. If
indexDetailsistrue, you can useindexDetailsKeyto filter index details by specifying the index key specification. Only the index that exactly matchesindexDetailsKeywill be returned.If no match is found,
indexDetailswill display statistics for all indexes.Use
getIndexes()to discover index keys. You cannot useindexDetailsKeywithindexDetailsName.indexDetailsNamestringOptional. If
indexDetailsistrue, you can useindexDetailsNameto filter index details by specifying the indexname. Only the index name that exactly matchesindexDetailsNamewill be returned.If no match is found,
indexDetailswill display statistics for all indexes.Use
getIndexes()to discover index names. You cannot useindexDetailsNamewithindexDetailsField.To specify just the
scalefactor, MongoDB supports the legacy format:db.collection.stats(<number>) Returns: A document that contains statistics on the specified collection. See collStatsfor a breakdown of the returned statistics.
Behavior
Scaled Sizes
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.
The scale factor rounds the affected size values to whole numbers.
Storage Engine
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 restore statistics after an unclean shutdown.
After an unclean shutdown:
Replica Set Member State Restriction
To run on a replica set member, collStats operations require the member
to be in PRIMARY or SECONDARY state. If the member
is in another state, such as STARTUP2, the
operation errors.
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.
In-Progress Indexes
The db.collection.stats() includes information on indexes currently
being built. For details, see:
Examples
Note
You can find the collection data used for these examples in our primer-dataset.json
Basic Stats Lookup
The following operation returns stats on the restaurants collection
in the test database:
db.restaurants.stats()
The operation returns:
{ "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" : [ ], "totalIndexSize" : 704512, "totalSize" : 10375168, "indexSizes" : { "_id_" : 241664, "cuisine_1" : 147456, "borough_1_cuisine_1" : 159744, "borough_1_address.zipcode_1" : 155648 }, "scaleFactor" : 1, "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" : "test.restaurants", "size" : 7380, "count" : 25359, "avgObjSize" : 298, "storageSize" : 9444, "freeStorageSize" : 6504, "capped" : false, "wiredTiger" : { ... }, "nindexes" : 4, "indexBuilds" : [ ], "totalIndexSize" : 688, "totalSize" : 10132, "indexSizes" : { "_id_" : 236, "cuisine_1" : 144, "borough_1_cuisine_1" : 156, "borough_1_address.zipcode_1" : 152 }, "scaleFactor" : 1024, "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.restaurants.stats( { indexDetails : true } )
The operation returns:
{ "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" : [ ], "totalIndexSize" : 704512, "totalSize" : 10375168, "indexSizes" : { "_id_" : 241664, "cuisine_1" : 147456, "borough_1_cuisine_1" : 159744, "borough_1_address.zipcode_1" : 155648 }, "scaleFactor" : 1, "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" : "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.
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" : "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" : [ ], "totalIndexSize" : 704512, "totalSize" : 10375168, "indexSizes" : { "_id_" : 241664, "cuisine_1" : 147456, "borough_1_cuisine_1" : 159744, "borough_1_address.zipcode_1" : 155648 }, "scaleFactor" : 1, "ok" : 1 }
For explanation of the output, see output details.