Mongo.startSession()¶

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Definition
Examples

Definition¶

Mongo.startSession(<options>)¶

New in version 3.6.

Starts a session for the connection. The mongo shell assigns the session id to commands associated with the session.

The startSession() method can take a document with session options. The options available are:

Field	Description
causalConsistency	Boolean. Enables or disables causal consistency for the session. `Mongo.startSession()` enables `causalConsistency` by default. After starting a session, you cannot modify its `causalConsistency` setting. Note The session may have causal consistency enabled even though the `Mongo` connection object may have causal consistency disabled or vice versa. To set causal consistency on the connection object, see `Mongo.setCausalConsistency()`.
readConcern	Document. Specifies the read concern. To modify the setting after starting a session, see `Sessions.getOptions().setReadConcern()`.
readPreference	Document. Specifies the read preference. The readPreference document contains the `mode` field and the optional `tags` field: copy { mode: <string>, tags: <array> } To modify the setting after starting a session, see `Sessions.getOptions().setReadPreference()`.
retryWrites	Boolean. Enables or disables the ability to retry writes upon encountering transient network errors. If you start the `mongo` shell with the `--retryWrites` option, `retryWrites` is enabled by default for `Mongo.startSession()`. After starting a session, you cannot modify its `retryWrites` setting.
writeConcern	Document. Specifies the write concern. To modify the setting after starting a session, see `Sessions.getOptions().setWriteConcern()`.

Examples¶

The following starts a session with causal consistency and retryable writes enabled on the Mongo connection object associated with the mongo shell’s global db variable:

copy

db = db.getMongo().startSession({retryWrites: true, causalConsistency: true}).getDatabase(db.getName());

← Mongo.setReadPref() Mongo.watch() →