getLastError¶

Definition¶

getLastError¶

在 2.6 版更改: A new protocol for write operations integrates write concerns with the write operations, eliminating the need for a separate getLastError command. Write methods now return the status of the write operation, including error information.

In previous versions, clients typically used the getLastError command in combination with the write operations to ensure that the write succeeds.

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 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.
`fsync`	Boolean	If `true`, wait for `mongod` to write this data to disk before returning. Defaults to false. In most cases, use the `j` option to ensure durability and consistency of the data set.
`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.

参见

Write Concern, Write Concern Reference, and 副本集确认型（Replica Acknowledged）.

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.

注解

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 textual description of the error.

getLastError.code¶: code reports the preceding operation’s error code.

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¶: n reports the number of documents updated or removed, if the preceding operation was an update or remove operation.

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.

在 2.6 版更改: Earlier versions of MongoDB included upserted only if _id was an ObjectId.

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

See

Write Concern Reference 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 getLastError.waited are equal.

Examples¶

Confirm Replication to Two Replica Set Members¶

The following example ensures the operation has replicated to two members (the primary and one other member):

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

Confirm Replication to a Majority of a Replica Set¶

The following example ensures the write operation has replicated to a majority of the configured members of the set.

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

在 2.6 版更改: In Master/Slave deployments, MongoDB treats w: "majority" as equivalent to w: 1. In earlier versions of MongoDB, w: "majority" produces an error in master/slave deployments.

Set a Timeout for a `getLastError` Response¶

Unless you specify a timeout, a getLastError command may block forever if MongoDB cannot satisfy the requested write concern. To specify a timeout of 5000 milliseconds, use an invocation that resembles the following:

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

When wtimeout is 0, the getLastError operation will never time out.

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