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$indexStats (aggregation)

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Definition

$indexStats

New in version 3.2.

Returns statistics regarding the use of each index for the collection. If running with access control, the user must have privileges that include indexStats action.

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

{ $indexStats: { } }

The return document includes the following fields:

Output Field Description
name Index name.
key Index key specification.
host The hostname and port of the mongod process.
accesses

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.

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

Note

Prior to version 3.2.3, the ops field value did not include $match or mapReduce operations that use indexes.

Behavior

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.

Example

For example, a collection orders contains the following documents:

{ "_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 } )

Run some queries against the collection:

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

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" : "item_1_quantity_1",
   "key" : {
      "item" : 1,
      "quantity" : 1
   },
   "host" : "examplehost.local:27017",
   "accesses" : {
      "ops" : NumberLong(1),
      "since" : ISODate("2015-10-02T14:31:53.685Z")
   }
}
{
   "name" : "_id_",
   "key" : {
      "_id" : 1
   },
   "host" : "examplehost.local:27017",
   "accesses" : {
      "ops" : NumberLong(0),
      "since" : ISODate("2015-10-02T14:31:32.479Z")
   }
}
{
   "name" : "type_1_item_1",
   "key" : {
      "type" : 1,
      "item" : 1
   },
   "host" : "examplehost.local:27017",
   "accesses" : {
      "ops" : NumberLong(1),
      "since" : ISODate("2015-10-02T14:31:58.321Z")
   }
}