planCacheClear¶

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Definition
Required Access
Examples

Definition¶

planCacheClear¶

Removes cached query plans for a collection. Specify a query shape to remove cached query plans for that shape. Omit the query shape to clear all cached query plans.

Tip

In the mongo Shell, this command can also be run through the PlanCache.clear and PlanCache.clearPlansByQuery helper methods.

Helper methods are convenient for mongo users, but they may not return the same level of information as database commands. In cases where the convenience is not needed or the additional return fields are required, use the database command.

The command has the following syntax:

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db.runCommand(
   {
      planCacheClear: <collection>,
      query: <query>,
      sort: <sort>,
      projection: <projection>
   }
)

The planCacheClear command has the following field:

Field	Type	Description
`query`	document	Optional. The query predicate of the query shape. Only the structure of the predicate, including the field names, are significant to the shape; the values in the query predicate are insignificant.
`projection`	document	Optional. The projection associated with the query shape.
`sort`	document	Optional. The sort associated with the query shape.

To see the query shapes for which cached query plans exist, see List Query Shapes.

Required Access¶

On systems running with authorization, a user must have access that includes the planCacheWrite action.

Examples¶

Clear Cached Plans for a Query Shape¶

If a collection orders has the following query shape:

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{
  "query" : { "qty" : { "$gt" : 10 } },
  "sort" : { "ord_date" : 1 },
  "projection" : { },
  "queryHash" : "9AAD95BE"  // Available starting in MongoDB 4.2
}

The following operation clears the query plan cached for the shape:

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db.runCommand(
   {
      planCacheClear: "orders",
      query: { "qty" : { "$gt" : 10 } },
      sort: { "ord_date" : 1 }
   }
)

Clear All Cached Plans for a Collection¶

The following example clears all the cached query plans for the orders collection:

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db.runCommand(
   {
      planCacheClear: "orders"
   }
)