getMore

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Definition

Compatibility
Syntax
Command Fields
Output
Behavior
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Definition

getMore: Use in conjunction with commands that return a cursor. For example, find and aggregate, to return subsequent batches of documents currently pointed to by the cursor.

Compatibility

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

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

Important

This command has limited support in M0, M2, and M5 clusters. For more information, see Unsupported Commands.

MongoDB Enterprise: The subscription-based, self-managed version of MongoDB
MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB

Syntax

The command has the following syntax:

db.runCommand(
   {
      getMore: <long>,
      collection: <string>,
      batchSize: <int>,
      maxTimeMS: <int>,
      comment: <any>
   }
)

Command Fields

The command accepts the following fields:

Field	Type	Description
`getMore`	long	The cursor identifier.
`collection`	string	The name of the collection over which the cursor is operating.
`batchSize`	positive integer	Optional. The number of documents to return in the batch. If `batchSize` is not set, `getMore` returns up to 16 megabytes of data. If `batchSize` is set, `getMore` returns the smaller of 16 megabytes of data or `batchSize` documents.
`maxTimeMS`	non-negative integer	Optional. Specifies the maximum time for the server to wait for new documents that match a tailable cursor query on a capped collection. `maxTimeMS` on a `getMore` for a tailable `awaitData` cursor is considered the same as `maxAwaitTimeMS()`. Drivers will only set this value on `getMore` for a tailable cursor on a capped collection with `awaitData` set to `true`. Otherwise, the command that creates the cursor sets `maxTimeMS`, which is the maximum amount of time that the initial operation, and any subsequent `getMore` operations, can spend cumulatively executing the query. For tailable cursors with `awaitData` set to `true`, the following is true: If no value is provided, the wait time defaults to `1` (1000 milliseconds). `maxTimeMS` on `getMore` specifies the maximum amount of time MongoDB waits for new documents to be inserted into the capped collection for that specific `getMore` command. `maxTimeMS` is set individually by the driver for each call to `getMore`. MongoDB terminates operations that exceed their allotted time limit using the same mechanism as `db.killOp()`. MongoDB only terminates an operation at one of its designated interrupt points. You cannot set `maxTimeMS` when calling `getMore` on a non-tailable cursor. Instead, set it using `maxTimeMS()` when you create the cursor. To use `getMore` with `maxTimeMS` on a tailable cursor, enable `awaitData` when you create the cursor using `cursor.tailable()`. Setting `maxTimeMS` on the command that creates a cursor only sets the time limit for that operation. Use `getMore` to set a limit on further operations. You can set or omit `maxTimeMS` for each call to `getMore`, and you don't have to use the same value. For a tailable cursor, a timeout on `getMore` retains the documents accumulated before the timeout occurred in the cursor. For a non-tailable cursor, a timeout raises an error.
`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: mongod log messages, in the `attr.command.cursor.comment` field. Database profiler output, in the `command.comment` field. `currentOp` output, in the `command.comment` field. A comment can be any valid BSON type (string, integer, object, array, etc). Note If omitted, `getMore` inherits any `comment` set on the originating `find` or `aggregate` command.

Output

The command returns a document that contains the cursor information as well as the next batch.

For example, running getMore on a cursor created by a find operation on a sharded cluster returns a document similar to this output:

{
   "cursor" : {
      "id" : NumberLong("678960441858272731"),
      "ns" : "test.contacts",
      "nextBatch" : [
         {
            "_id" : ObjectId("5e8e501e1a32d227f9085857"),
            "zipcode" : "220000"
         }
      ],
      "partialResultsReturned" : true,
      "postBatchResumeToken": "< Resume Token >"
   },
   "ok" : 1,
   "operationTime" : Timestamp(1586385239, 2),
   "$clusterTime" : {
      "clusterTime" : Timestamp(1586385239, 2),
      "signature" : {
         "hash" : BinData(0,"lLjejeW6AQGReR9x1PD8xU+tP+A="),
         "keyId" : NumberLong("6813467763969884181")
      }
   }
}

Field

Description

cursor

Contains the cursor information, including the cursor ID as well as the nextBatch of documents.

If find (or subsequent getMore commands) returns partial results because the queried shard(s) aren't available, the find output includes a partialResultsReturned indicator field. If the queried shards are available for the initial find command, but one or more shards become unavailable for subsequent getMore commands, only the getMore commands that run while the shards aren't available include partialResultsReturned in their output.

The postBatchResumeToken field can be used with the $changeStream pipeline to start or resume a change stream from this point.

"ok"

Indicates whether the command has succeeded (1) or failed (0).

In addition to these fields, the db.runCommand() response includes the following information for replica sets and sharded clusters:

$clusterTime
operationTime

See db.runCommand() Response for details.

Behavior

Access Control

If authentication is enabled, you can only run getMore against cursors you created.

Sessions

For cursors created inside a session, you cannot call getMore outside the session.

Similarly, for cursors created outside of a session, you cannot call getMore inside a session.

Transactions

For multi-document transactions:

For cursors created outside of a transaction, you cannot call getMore inside the transaction.
For cursors created in a transaction, you cannot call getMore outside the transaction.

Slow Queries

Starting in MongoDB 5.1, when a getMore command is logged as a slow query, the queryHash and planCacheKey fields are added to the slow query log message and the profiler log message.

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