dbStats¶

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Definition
Behavior
Output

Definition¶

dbStats¶

The dbStats command returns storage statistics for a given database. The command has the following syntax:

db.runCommand( {
   dbStats: 1,
   scale: <number>       //Optional
} )

The dbStats command takes the following fields:

Parameter Description

dbStats 1

scale

Optional. The scale factor for the various size data. The scale defaults to 1 to return size data in bytes. To display kilobytes rather than bytes, specify a scale value of 1024.

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 uses 1023 as the scale factor.

Starting in version 4.2, the output includes the scaleFactor used to scale the size values.

In the mongo shell, the db.stats() function provides a wrapper around dbStats.

Behavior¶

The time required to run the command depends on the total size of the database. Because the command must touch all data files, the command may take several seconds to run.

Accuracy after Unexpected Shutdown¶

After an unclean shutdown of a mongod using the Wired Tiger storage engine, count and size statistics reported by dbStats 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 the correct statistics after an unclean shutdown.

Replica Set Member State Restriction¶

Starting in MongoDB 4.4, to run on a replica set member, dbStats operations require the member to be in PRIMARY or SECONDARY state. If the member is in another state, such as STARTUP2, the operation errors.

In previous versions, the operations can also be run when the member is in STARTUP2. However, the operations wait until the member transitions to RECOVERING.

Output¶

dbStats.db¶: Contains the name of the database.

dbStats.collections¶: Contains a count of the number of collections in that database.

dbStats.views¶: Contains a count of the number of views in that database.

dbStats.objects¶: Contains a count of the number of objects (i.e. documents) in the database across all collections.

dbStats.avgObjSize¶: The average size of each document in bytes. This is the dataSize divided by the number of documents. The scale argument does not affect the avgObjSize value.

dbStats.dataSize¶

The total size of the uncompressed data held in this database. The dataSize decreases when you remove documents.

For databases using the WiredTiger storage engine, dataSize may be larger than storageSize if compression is enabled. The dataSize decreases when documents shrink.

dbStats.storageSize¶

The total amount of space allocated to collections in this database for document storage. The storageSize does not decrease as you remove or shrink documents. This value may be smaller than dataSize for databases using the WiredTiger storage engine with compression enabled.

storageSize does not include the index size. See indexSize for index sizing.

dbStats.indexes¶: Contains a count of the total number of indexes across all collections in the database.

dbStats.indexSize¶: The total size of all indexes created on this database.

dbStats.totalSize¶: The sum of the storageSize and indexSize.

New in version 4.4.

dbStats.scaleFactor¶

The scale value used by the command.

If you specified 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 uses 1023 as the scale factor.

New in version 4.2.

dbStats.fsUsedSize¶: New in version 3.6.

Total size of all disk space in use on the filesystem where MongoDB stores data.

See also

--dbpath

dbStats.fsTotalSize¶: New in version 3.6.

Total size of all disk capacity on the filesystem where MongoDB stores data.

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