The MongoDB\Driver\ReadConcern class

(mongodb >=1.1.0)

Introduction

MongoDB\Driver\ReadConcern controls the level of isolation for read operations for replica sets and replica set shards. This option requires the WiredTiger storage engine and MongoDB 3.2 or later.

Class synopsis

final MongoDB\Driver\ReadConcern implements MongoDB\BSON\Serializable {
/* Constants */
const string LINEARIZABLE = "linearizable" ;
const string LOCAL = "local" ;
const string MAJORITY = "majority" ;
/* Methods */
final public object bsonSerialize ( void )
final public __construct ([ string $level ] )
final public string|null getLevel ( void )
final public boolean isDefault ( void )
}

Predefined Constants

MongoDB\Driver\ReadConcern::LINEARIZABLE

A linearizable read avoids returning reads from a stale primary (one that has already been superseded by a new primary but doesn't know it yet). It is important to note that this read concern level does not by itself produce linearizable reads; they must be issued in conjunction with MongoDB\Driver\WriteConcern::MAJORITY writes to the same document(s) in order to be linearizable.

MongoDB\Driver\ReadConcern::LOCAL

Queries using this read concern will return the node's most recent copy of the data. This provides no guarantee that the data has been written to a majority of the nodes (i.e. it may be rolled back). This is the default read concern for MongoDB.

MongoDB\Driver\ReadConcern::MAJORITY

Queries using this read concern will return the node's most recent copy of the data confirmed as having been written to a majority of the nodes (i.e. the data cannot be rolled back).

Changelog

Version Description
1.2.0

Added the MongoDB\Driver\ReadConcern::LINEARIZABLE constant.

Implements MongoDB\BSON\Serializable.

Table of Contents

add a note add a note

User Contributed Notes

There are no user contributed notes for this page.
To Top