planCacheClear
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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 thePlanCache.clear()
andPlanCache.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:
db.runCommand( { planCacheClear: <collection>, query: <query>, sort: <sort>, projection: <projection>, comment: <any> } ) The
planCacheClear
command has the following field:FieldTypeDescriptionquery
documentOptional. 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
documentOptional. The projection associated with the query shape.sort
documentOptional. The sort associated with the query shape.comment
anyOptional. A user-provided comment to attach to this command. Once set, this comment appears alongside records of this command in the following locations:
mongod log messages, in the
attr.command.cursor.comment
field.Database profiler output, in the
command.comment
field.currentOp
output, in thecommand.comment
field.
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 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:
{ "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" } )