> For the complete MongoDB documentation index, see www.mongodb.com/docs/llms.txt

# Measure Index Use

## Get Index Access Information with `$indexStats`

Use the [`$indexStats`](https://www.mongodb.com/docs/manual/reference/operator/aggregation/indexstats.md#mongodb-pipeline-pipe.-indexStats) aggregation stage to get statistics regarding the use of each index for a collection. For example, the following aggregation operation returns statistics on the index use on the `orders` collection:

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

**Warning:**

[`$indexStats`](https://www.mongodb.com/docs/manual/reference/operator/aggregation/indexstats.md#mongodb-pipeline-pipe.-indexStats) reports index usage metrics in the [accesses](https://www.mongodb.com/docs/manual/reference/operator/aggregation/indexstats.md#std-label-indexStats-output-accesses) field only for the node where the query runs. For more comprehensive index usage statistics, run [`$indexStats`](https://www.mongodb.com/docs/manual/reference/operator/aggregation/indexstats.md#mongodb-pipeline-pipe.-indexStats) on each node in the cluster.

**See also:**

[`$indexStats`](https://www.mongodb.com/docs/manual/reference/operator/aggregation/indexstats.md#mongodb-pipeline-pipe.-indexStats)

## Return Query Plan with `explain()`

Use the [`db.collection.explain()`](https://www.mongodb.com/docs/manual/reference/method/db.collection.explain.md#mongodb-method-db.collection.explain) or the [`cursor.explain()`](https://www.mongodb.com/docs/manual/reference/method/cursor.explain.md#mongodb-method-cursor.explain) method in [executionStats](https://www.mongodb.com/docs/manual/reference/method/db.collection.explain.md#std-label-explain-method-executionStats) mode to return statistics about the query process, including the index used, the number of documents scanned, and the time the query takes to process in milliseconds.

Run [`db.collection.explain()`](https://www.mongodb.com/docs/manual/reference/method/db.collection.explain.md#mongodb-method-db.collection.explain) or the [`cursor.explain()`](https://www.mongodb.com/docs/manual/reference/method/cursor.explain.md#mongodb-method-cursor.explain) method in [allPlansExecution](https://www.mongodb.com/docs/manual/reference/method/db.collection.explain.md#std-label-explain-method-allPlansExecution) mode to view partial execution statistics collected during plan selection.

**See also:**

[planCacheKey](https://www.mongodb.com/docs/manual/core/query-plans.md#std-label-plan-cache-key)

## Control Index Use with `hint()`

To *force* MongoDB to use a particular index for a [`db.collection.find()`](https://www.mongodb.com/docs/manual/reference/method/db.collection.find.md#mongodb-method-db.collection.find) operation, specify the index with the [`hint()`](https://www.mongodb.com/docs/manual/reference/method/cursor.hint.md#mongodb-method-cursor.hint) method. Append the [`hint()`](https://www.mongodb.com/docs/manual/reference/method/cursor.hint.md#mongodb-method-cursor.hint) method to the [`find()`](https://www.mongodb.com/docs/manual/reference/method/db.collection.find.md#mongodb-method-db.collection.find) method. Consider the following example:

```javascript
db.people.find(
   { name: "John Doe", zipcode: { $gt: "63000" } }
).hint( { zipcode: 1 } )
```

To view the execution statistics for a specific index, append to the [`db.collection.find()`](https://www.mongodb.com/docs/manual/reference/method/db.collection.find.md#mongodb-method-db.collection.find) the [`hint()`](https://www.mongodb.com/docs/manual/reference/method/cursor.hint.md#mongodb-method-cursor.hint) method followed by [`cursor.explain()`](https://www.mongodb.com/docs/manual/reference/method/cursor.explain.md#mongodb-method-cursor.explain), e.g.:

```javascript
db.people.find(
   { name: "John Doe", zipcode: { $gt: "63000" } }
).hint( { zipcode: 1 } ).explain("executionStats")
```

Or, append [`hint()`](https://www.mongodb.com/docs/manual/reference/method/cursor.hint.md#mongodb-method-cursor.hint) method to [`db.collection.explain().find()`:](https://www.mongodb.com/docs/manual/reference/method/db.collection.explain.md#mongodb-method-db.collection.explain)

```javascript
db.people.explain("executionStats").find(
   { name: "John Doe", zipcode: { $gt: "63000" } }
).hint( { zipcode: 1 } )
```

Specify the `$natural` operator to the [`hint()`](https://www.mongodb.com/docs/manual/reference/method/cursor.hint.md#mongodb-method-cursor.hint) method to prevent MongoDB from using *any* index:

```javascript
db.people.find(
   { name: "John Doe", zipcode: { $gt: "63000" } }
).hint( { $natural: 1 } )
```

## Index Metrics

In addition to the [`$indexStats`](https://www.mongodb.com/docs/manual/reference/operator/aggregation/indexstats.md#mongodb-pipeline-pipe.-indexStats) aggregation stage, MongoDB provides various index statistics that you may want to consider when analyzing index use for your database:

- In the output of [`serverStatus`:](https://www.mongodb.com/docs/manual/reference/command/serverstatus.md#mongodb-dbcommand-dbcmd.serverStatus)

  - [`metrics.queryExecutor.scanned`](https://www.mongodb.com/docs/manual/reference/command/serverstatus.md#mongodb-serverstatus-serverstatus.metrics.queryExecutor.scanned)

  - [`metrics.operation.scanAndOrder`](https://www.mongodb.com/docs/manual/reference/command/serverstatus.md#mongodb-serverstatus-serverstatus.metrics.operation.scanAndOrder)

- In the output of [`collStats`:](https://www.mongodb.com/docs/manual/reference/command/collstats.md#mongodb-dbcommand-dbcmd.collStats)

  - [`totalIndexSize`](https://www.mongodb.com/docs/manual/reference/command/collstats.md#mongodb-data-collStats.totalIndexSize)

  - [`indexSizes`](https://www.mongodb.com/docs/manual/reference/command/collstats.md#mongodb-data-collStats.indexSizes)

- In the output of [`dbStats`:](https://www.mongodb.com/docs/manual/reference/command/dbstats.md#mongodb-dbcommand-dbcmd.dbStats)

  - [`dbStats.indexes`](https://www.mongodb.com/docs/manual/reference/command/dbstats.md#mongodb-data-dbStats.indexes)

  - [`dbStats.indexSize`](https://www.mongodb.com/docs/manual/reference/command/dbstats.md#mongodb-data-dbStats.indexSize)