`$collStats`

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Syntax

Fields
Output
Examples
Errors

$collStats returns statistics for a given collection. $collstats must be the first stage in the aggregation pipeline. For more information, see $collStats. In Data Federation, $collStats can only be used to retrieve information about the partitions for a given collection or view.

Syntax

In Atlas Data Federation, $collStats accepts an empty document. It supports the optional field count only and returns an error if an unsupported option is specified.

db.<collection-name>|<view-name>.aggregate([{ "$collStats" : { "count" : {} } }])

Fields

Field	type	Description	Necessity
`count`	document	Adds the total number of documents in the partitions to the return document.	Optional

Output

$collStats returns the following fields in the document for each partition:

Field	Type	Description
`count`	number	The total number of documents in the partition. This is returned only if you specify the `count` option.
`ns`	string	The namespace of the current collection or view in the format `[database].[collection\|view]`.
`partition`	document	The details about the partition such as the source, format, size, and partition attributes, if any.
`partition.format`	string	The format of the file. Value can be any of the Supported Data Formats for data in S3 bucket or `MONGO` for data in the Atlas cluster.
`partition.attributes`	document	The partition attributes for this partition defined in the `path` for S3 partitions. An empty document indicates that there are no partition attributes in the partition's data source.
`partition.size`	int	The size of the partition.
`partition.source`	string	The source for the partition. The value can be one of the following: The path to the file on S3. The cluster name for partitions on Atlas.

Examples

Errors

An error similar to the following is returned if the collStats argument document contains any of the options allowed by the MongoDB server but not by Atlas Data Federation.

{
       "ok" : 0,
       "errmsg" : "$collStats param 'latencyStats' is not valid for Data Lake, correlationID = 1622929884a47d16f4888a1c",
       "code" : 9,
       "codeName" : "FailedToParse"
}

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