planCacheClear
Definition
planCacheClearRemoves 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
mongosh, this command can also be run through thePlanCache.clear()andPlanCache.clearPlansByQuery()helper methods.Helper methods are convenient for
mongoshusers, 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.
Syntax
The command has the following syntax:
db.runCommand( { planCacheClear: <collection>, query: <query>, sort: <sort>, projection: <projection>, comment: <any> } )
Command Fields
The command takes the following optional fields:
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. |
comment | any | Optional. A user-provided comment to attach to this command. Once set, this comment appears alongside records of this command in the following locations:
A comment can be any valid BSON type (string, integer, object, array, etc). New in version 4.4. |
To see the query shapes for which cached query plans exist, see Examples.
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:
{ "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 the
orders collection:
db.runCommand( { planCacheClear: "orders" } )