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Database Methods

db.stats()

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  • Description
  • Behavior
  • Examples

Description

db.stats(scale)

Returns statistics that reflect the use state of a single database.

The db.stats() method is a wrapper around the dbStats database command.

Parameters

The db.stats() method has the following optional parameters:

Parameter
Type
Description
number

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.

number

Optional. To return information on free space allocated to collections, set freeStorage to 1.

If the instance has a large number of collections or indexes, obtaining free space usage data may cause processing delays. To gather db.stats() data without free space details, either set freeStorage to 0 or do not include the parameter.

Output

The db.stats() method returns a document with statistics about the database system's state. A complete listing, including freeStorage details, resembles the following:

{
  db: 'test',
  collections: 2,
  views: 0,
  objects: 1689,
  avgObjSize: 52.56542332741267,
  dataSize: 86.7021484375,
  storageSize: 100,
  freeStorageSize: 32,
  indexes: 2,
  indexSize: 116,
  indexFreeStorageSize: 36,
  totalSize: 216,
  totalFreeStorageSize: 68,
  scaleFactor: 1024,
  fsUsedSize: 60155820,
  fsTotalSize: 61255492,
  ok: 1,
  '$clusterTime': {
    clusterTime: Timestamp({ t: 1646085664, i: 1 }),
    signature: {
      hash: Binary(Buffer.from("0000000000000000000000000000000000000000", "hex"), 0),
      keyId: Long("0")
    }
  },
  operationTime: Timestamp({ t: 1646085664, i: 1 })
}

For an explanation of the output, see Output.

Behavior

Accuracy after Unexpected Shutdown

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

  • validate updates the count statistic in the collStats output with the latest value.

  • Other statistics like the number of documents inserted or removed in the collStats output are estimates.

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 also run when the member is in STARTUP2. The operations wait until the member transitioned to RECOVERING.

Examples

Scale Output Values

To to return values in kilobytes, set the scale to 1024:

db.stats(1024)

Note

The scale factor rounds values to whole numbers.

Return a Single Value

To return a single value, such as indexSize, append the field name to db.stats().

db.stats().indexSize
db.stats(1024).indexSize

The output shows the difference between the original and scaled values.

118784
116

Return Information on Free Space Allocated to Collections

To return information on free space allocated to collections, pass the freeStorage parameter to db.stats().

The following example returns the indexFreeStorageSize in kilobytes:

db.stats( { freeStorage: 1, scale: 1024 } ).indexFreeStorageSize

Back

db.shutdownServer()