MongoDB\Driver\ReadConcern
PHP Manual

MongoDB\Driver\ReadConcern::__construct

(mongodb >=1.0.0)

MongoDB\Driver\ReadConcern::__constructConstruct immutable ReadConcern

说明

final public MongoDB\Driver\ReadConcern::__construct ([ string $level ] )

Creates a new ReadConcern.

参数

level

Read concern
Value Description
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A linearizable read avoids returning reads from a stale primary (one that has already been superseded by a new primary but doesn't know it yet).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).

错误/异常

范例

Example #1 MongoDB\Driver\ReadConcern::__construct() example

<?php

/* Unspecified read isolation level (uses the server's default behavior) */
$rc = new MongoDB\Driver\ReadConcern();

/* Request read isolation from a single replica set node */
$rc = new MongoDB\Driver\ReadConcern(MongoDB\Driver\ReadConcern::LOCAL);

/* Request read isolation from a majority of the replica set nodes */
$rc = new MongoDB\Driver\ReadConcern(MongoDB\Driver\ReadConcern::MAJORITY);

?>

参见


MongoDB\Driver\ReadConcern
PHP Manual