db.collection.estimatedDocumentCount()
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Definition
db.collection.estimatedDocumentCount(options)
Important
mongosh Method
This is a
mongosh
method. This is not the documentation forNode.js
or other programming language specific driver methods.In most cases,
mongosh
methods work the same way as the legacymongo
shell methods. However, some legacy methods are unavailable inmongosh
.For the legacy
mongo
shell documentation, refer to the documentation for the corresponding MongoDB Server release:For MongoDB API drivers, refer to the language specific MongoDB driver documentation.
New in version 4.0.3.
Returns the count of all documents in a collection or view. The method wraps the
count
command.db.collection.estimatedDocumentCount( <options> ) ParameterTypeDescriptionoptionsdocumentOptional. Extra options that affect the count behavior.The
options
document can contain the following:FieldTypeDescriptionmaxTimeMS
integerOptional. The maximum amount of time to allow the count to run.
Behavior
Mechanics
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.
Sharded Clusters
On a sharded cluster, the resulting count will not correctly filter out orphaned documents.
Unclean Shutdown
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:
Client Disconnection
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
.
Example
The following example uses
db.collection.estimatedDocumentCount()
to retrieve the count of
all documents in the orders
collection:
db.orders.estimatedDocumentCount({})