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db.collection.estimatedDocumentCount()

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  • Definition
  • Compatibility
  • Behavior
  • Example

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db.collection.estimatedDocumentCount(options)

Returns the count of all documents in a collection or view.

db.collection.estimatedDocumentCount( <options> )
Parameter
Type
Description
options
document
Optional. Extra options that affect the count behavior.

The options document can contain the following:

Field
Type
Description
maxTimeMS
integer
Optional. The maximum amount of time to allow the count to run.

This method is available in deployments hosted in the following environments:

  • MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud

Note

This command is supported in all MongoDB Atlas clusters. For information on Atlas support for all commands, see Unsupported Commands.

  • MongoDB Enterprise: The subscription-based, self-managed version of MongoDB

  • MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB

db.collection.estimatedDocumentCount() does not take a query filter and instead uses metadata to return the count for a collection.

For a view:

  • There is no metadata.

  • The document count is calculated by executing the aggregation pipeline in the view definition.

  • There is no fast estimated document count.

On a sharded cluster, the resulting count will not correctly filter out orphaned documents.

This section only applies to collections.

After an unclean shutdown, the count may be incorrect.

After an unclean shutdown of a mongod using the Wired Tiger storage engine, count statistics reported by db.collection.estimatedDocumentCount() 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:

Starting in MongoDB 4.2, if the client that issued db.collection.estimatedDocumentCount() disconnects before the operation completes, MongoDB marks db.collection.estimatedDocumentCount() for termination using killOp.

When you use db.collection.estimatedDocumentCount() in a transaction, the resulting count will not filter out any uncommitted multi-document transactions.

The following example uses db.collection.estimatedDocumentCount() to retrieve the count of all documents in the orders collection:

db.orders.estimatedDocumentCount({})

Tip

See also:

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