getLastError

Definition

getLastError

Changed in version 2.6: A new protocol for write operations integrates write concerns with the write operations, eliminating the need for a separate getLastError. Most write methods now return the status of the write operation, including error information. In previous versions, clients typically used the getLastError in combination with a write operation to verify that the write succeeded.

Returns the error status of the preceding write operation on the current connection.

getLastError uses the following prototype form:

{ getLastError: 1 }

getLastError uses the following fields:

Field	Type	Description
j	boolean	If true, wait for the next journal commit before returning, rather than waiting for a full disk flush. If mongod does not have journaling enabled, this option has no effect. If this option is enabled for a write operation, mongod will wait no more than 1/3 of the current commitIntervalMs before writing data to the journal.
w	integer or string	When running with replication, this is the number of servers to replicate to before returning. A w value of 1 indicates the primary only. A w value of 2 includes the primary and at least one secondary, etc. In place of a number, you may also set w to majority to indicate that the command should wait until the latest write propagates to a majority of the voting replica set members. If using w, you should also use wtimeout. Specifying a value for w without also providing a wtimeout may cause getLastError to block indefinitely.
wtimeout	integer	Optional. Milliseconds. Specify a value in milliseconds to control how long to wait for write propagation to complete. If replication does not complete in the given timeframe, the getLastError command will return with an error status.
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). New in version 4.4.

Tip

Write Concern

Output

Each getLastError command returns a document containing a subset of the fields listed below.

getLastError.ok

ok is true when the getLastError command completes successfully.

Note

A value of true does not indicate that the preceding operation did not produce an error.

getLastError.err

err is null unless an error occurs. When there was an error with the preceding operation, err contains a string identifying the error.

getLastError.ns

If the error is a duplicate key error, returns the namespace of the collection.

New in version 4.4.

getLastError.index

If the error is a duplicate key error, returns the index whose unique key constraint is violated.

New in version 4.4.

getLastError.errmsg

errmsg contains the description of the error. errmsg only appears if there was an error with the preceding operation.

getLastError.code

code reports the preceding operation's error code. For description of the error, see err and errmsg.

getLastError.connectionId

The identifier of the connection.

getLastError.lastOp

When issued against a replica set member and the preceding operation was a write or update, lastOp is the optime timestamp in the oplog of the change.

getLastError.n

If the preceding operation was an update or a remove operation, but not a findAndModify operation, n reports the number of documents matched by the update or remove operation.

For a remove operation, the number of matched documents will equal the number removed.

For an update operation, if the operation results in no change to the document, such as setting the value of the field to its current value, the number of matched documents may be smaller than the number of documents actually modified. If the update includes the upsert:true option and results in the creation of a new document, n returns the number of documents inserted.

n is 0 if reporting on an update or remove that occurs through a findAndModify operation.

getLastError.syncMillis

syncMillis is the number of milliseconds spent waiting for the write to disk operation (e.g. write to journal files).

getLastError.shards

When issued against a sharded cluster after a write operation, shards identifies the shards targeted in the write operation. shards is present in the output only if the write operation targets multiple shards.

getLastError.singleShard

When issued against a sharded cluster after a write operation, identifies the shard targeted in the write operation. singleShard is only present if the write operation targets exactly one shard.

getLastError.updatedExisting

updatedExisting is true when an update affects at least one document and does not result in an upsert.

getLastError.upserted

If the update results in an insert, upserted is the value of _id field of the document.

getLastError.wnote

If set, wnote indicates that the preceding operation's error relates to using the w parameter to getLastError.

Tip

See:

Write Concern for more information about w values.

getLastError.wtimeout

wtimeout is true if the getLastError timed out because of the wtimeout setting to getLastError.

getLastError.waited

If the preceding operation specified a timeout using the wtimeout setting to getLastError, then waited reports the number of milliseconds getLastError waited before timing out.

getLastError.wtime

getLastError.wtime is the number of milliseconds spent waiting for the preceding operation to complete. If getLastError timed out, wtime and waited are equal.

getLastError.writtenTo

If writing to a replica set, writtenTo is an array that contains the hostname and port number of the members that confirmed the previous write operation, based on the value of the w field in the command.

Examples

db.runCommand( { getLastError: 1, w: 2, wtimeout:5000 } )

db.runCommand( { getLastError: 1, w: "majority", wtimeout:5000 } )