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$indexStats (aggregation)

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  • Definition
  • Behavior
  • Example
$indexStats

New in version 3.2.

Returns statistics regarding the use of each index for the collection. If running with access control, authenticate as a user with at least the clusterMonitor role.

The $indexStats stage takes an empty document and has the following syntax:

{ $indexStats: { } }

For each index, the return document includes the following fields:

Output Field
Description
name
Index name.

Index key specification.

See also: spec.

The hostname and port of the mongod process.

Statistics on the index use:

  • ops is the number of operations that used the index.

  • since is the time from which MongoDB gathered the statistics.

The name of the shard associated with the host

Only available for a sharded cluster.

The full specification document for the index, which includes the index key and index properties.

The index option hidden is only included if the value is true.

Indicates if the index is currently being built.

Only available if true.

The statistics reported by the accesses field only includes index access driven by user requests. It does not include internal operations like deletion via TTL Indexes or chunk split and migration operations.

  • $indexStats must be the first stage in an aggregation pipeline.

  • $indexStats is not allowed in transactions.

  • Statistics for an index reset on mongod restart or index drop and recreation.

  • Modification of an existing index (see collMod command) resets the statistics for that index.

For example, a collection orders contains the following documents:

db.orders.insertMany( [
{ _id : 1, item : "abc", price : 12, quantity : 2, type: "apparel" },
{ _id : 2, item : "jkl", price : 20, quantity : 1, type: "electronics" },
{ _id : 3, item : "abc", price : 10, quantity : 5, type: "apparel" }
] )

Create the following two indexes on the collection:

db.orders.createIndex( { item: 1, quantity: 1 } )
db.orders.createIndex( { type: 1, item: 1 } )
db.orders.createIndex(
{ price: 1 },
{ partialFilterExpression: { type: "apparel" } }
)

Run some queries against the collection:

db.orders.find( { type: "apparel"} )
db.orders.find( { item: "abc" } ).sort( { quantity: 1 } )
db.orders.find( { price: { $gt: 10 } } )

To view statistics on the index use on the orders collection, run the following aggregation operation:

db.orders.aggregate( [ { $indexStats: { } } ] )

The operation returns a document that contains usage statistics for each index:

[
{
name: 'type_1_item_1',
key: { type: 1, item: 1 },
host: 'examplehost.local:27018',
accesses: { ops: Long("1"), since: ISODate("2024-05-02T15:07:21.420Z") },
shard: "shardA",
spec: { v: 2, key: { type: 1, item: 1 }, name: 'type_1_item_1' }
},
{
name: 'item_1_quantity_1',
key: { item: 1, quantity: 1 },
host: 'examplehost.local:27018',
accesses: { ops: Long("1"), since: ISODate("2024-05-02T15:07:21.254Z") },
shard: "shardA",
spec: { v: 2, key: { item: 1, quantity: 1 }, name: 'item_1_quantity_1' }
},
{
name: '_id_',
key: { _id: 1 },
host: 'examplehost.local:27018',
accesses: { ops: Long("0"), since: ISODate("2024-05-02T15:07:13.274Z") },
shard: "shardA",
spec: { v: 2, key: { _id: 1 }, name: '_id_' }
},
{
name: 'price_1',
key: { price: 1 },
host: 'examplehost.local:27018',
accesses: { ops: Long("0"), since: ISODate("2024-05-02T15:07:54.847Z") },
shard: "shardA",
spec: {
v: 2,
key: { price: 1 },
name: 'price_1',
partialFilterExpression: { type: 'apparel' }
}
}
]

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