dbStats¶

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Definition
Behavior
Output

Definition¶

dbStats¶

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

{ dbStats: 1, scale: 1 }

The values of the options above do not affect the output of the command. The scale option allows you to specify how to scale byte values. For example, a scale value of 1024 will display the results in kilobytes rather than in bytes:

{ dbStats: 1, scale: 1024 }

Note

Scaling rounds values to whole numbers.

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.

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.

Output¶

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

dbStats.collections¶: Contains a count of the number of collections 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.

dbStats.dataSize¶: The total size in bytes of the data held in this database including the padding factor. The scale argument affects this value. The dataSize will not decrease when documents shrink, but will decrease when you remove documents.

dbStats.storageSize¶: The total amount of space in bytes allocated to collections in this database for document storage. The scale argument affects this value. The storageSize does not decrease as you remove or shrink documents.

dbStats.numExtents¶: Contains a count of the number of extents in the database across all collections.

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

dbStats.indexSize¶: The total size in bytes of all indexes created on this database. The scale arguments affects this value.

dbStats.fileSize¶

The total size in bytes of the data files that hold the database. This value includes preallocated space and the padding factor. The value of fileSize only reflects the size of the data files for the database and not the namespace file.

The scale argument affects this value. Only present when using the mmapv1 storage engine.

dbStats.nsSizeMB¶

The total size of the namespace files (i.e. that end with .ns) for this database. You cannot change the size of the namespace file after creating a database, but you can change the default size for all new namespace files with the nsSize runtime option.

Only present when using the mmapv1 storage engine.