indexStats.md

indexStats()

Return how often indexes accessed and touch. For example:

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

will output:

{
   "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")
   }
}

The benefit of indexStats() are:

• Find hot index which is extensively used to do many operations.
• Find cold index which is rarely used.

The behavior of indexStats() are:

• accesses.ops will be incremented if find operations triggered, including update() which is required to find matched document at first.
• Each member on replica set has its own version of indexStats().

For more information please read the documentation.