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killCursors

On this page

  • Definition
  • Compatibility
  • Syntax
  • Command Fields
  • Required Access
  • killCursors and Transactions
  • Example

Definition

killCursors

Kills the specified cursor or cursors for a collection. MongoDB drivers use the killCursors command as part of the client-side cursor implementation.

Warning

Applications typically should not run the killCursors command directly. Instead, let the driver automatically handle cursor management.

The killCursors command must be run against the database of the collection whose cursors you wish to kill.

To run killCursors, use the db.runCommand( { <command> } ) method.

Compatibility

This command is available in deployments hosted in the following environments:

  • MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud

Note

This command is supported in all MongoDB Atlas clusters. For information on Atlas support for all commands, see Unsupported Commands.

Syntax

The command has the following syntax:

db.runCommand(
   {
     killCursors: <collection>,
     cursors: [ <cursor id1>, ... ], comment: <any>
   }
)

Command Fields

The command takes the following fields:

Field
Type
Description
killCursors
string
The name of the collection.
cursors
array
The ids of the cursors to kill.
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).

Required Access

Kill Own Cursors

Users can always kill their own cursors regardless of whether they have the killCursors privilege. Cursors are associated with the users at the time of cursor creation.

Kill Any Cursor

If a user has the killAnyCursor privilege, they can kill cursors created by any user.

Atlas Required Access

To see which Atlas roles and privileges grant the killAnyCursor privilege, see Built-In Roles and Privileges in the Atlas documentation.

killCursors and Transactions

You cannot specify the killCursors command as the first operation in a transaction.

Additionally, if you run the killCursors command within a transaction, the server immediately stops the specified cursors. It does not wait for the transaction to commit.

Example

Consider the following find operation on the test.restaurants collection:

use test
db.runCommand(
   { find: "restaurants",
     filter: { stars: 5 },
     projection: { name: 1, rating: 1, address: 1 },
     sort: { name: 1 },
     batchSize: 5
   }
)

which returns the following:

{
   "waitedMS" : NumberLong(0),
   "cursor" : {
      "firstBatch" : [
         {
            "_id" : ObjectId("57506d63f578028074723dfd"),
            "name" : "Cakes and more"
         },
         {
            "_id" : ObjectId("57506d63f578028074723e0b"),
            "name" : "Pies and things"
         },
         {
            "_id" : ObjectId("57506d63f578028074723e1d"),
            "name" : "Ice Cream Parlour"
         },
         {
            "_id" : ObjectId("57506d63f578028074723e65"),
            "name" : "Cream Puffs"
         },
         {
            "_id" : ObjectId("57506d63f578028074723e66"),
            "name" : "Cakes and Rolls"
         }
      ],
      "id" : NumberLong("18314637080"),
      "ns" : "test.restaurants"
   },
   "ok" : 1
}

To kill this cursor, use the killCursors command.

use test
db.runCommand( { killCursors: "restaurants", cursors: [ NumberLong("18314637080") ] } )

killCursors returns the following operation details:

{
   "cursorsKilled" : [
      NumberLong("18314637080")
   ],
   "cursorsNotFound" : [ ],
   "cursorsAlive" : [ ],
   "cursorsUnknown" : [ ],
   "ok" : 1
}

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