(mongodb >=1.0.0)
MongoDB\Driver\ReadConcern::__construct — Construct immutable ReadConcern
$level
] )Creates a new ReadConcern.
level
| 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superseded by a new primary but doesn't know it yet).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). |
Пример #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);
?>