planCacheClear

planCacheClear

Definition

planCacheClear

New in version 2.6.

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

The command has the following syntax:

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

The planCacheClear command has the following field:

FieldTypeDescriptionquerydocumentOptional. The query predicate of the query shape. Only the structureof the predicate, including the field names, are significant to theshape; the values in the query predicate are insignificant.projectiondocumentOptional. The projection associated with the query shape.sortdocumentOptional. The sort associated with the query shape.

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

Required Access

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

Examples

Clear Cached Plans for a Query Shape

If a collection orders has the following query shape:

{
  "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:

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 theorders collection:

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