MongoCommandCursor::setReadPreference

Set the read preference for this command

Description

public MongoCommandCursor MongoCommandCursor::setReadPreference ( string $read_preference [, array $tags ] )

Parameters

read_preference: The read preference mode: MongoClient::RP_PRIMARY, MongoClient::RP_PRIMARY_PREFERRED, MongoClient::RP_SECONDARY, MongoClient::RP_SECONDARY_PREFERRED, or MongoClient::RP_NEAREST.
tags: An array of zero or more tag sets, where each tag set is itself an array of criteria used to match tags on replica set members.

Return Values

Returns this cursor.

Errors/Exceptions

Emits E_WARNING if either parameter is invalid, or if one or more tag sets are provided with the MongoClient::RP_PRIMARY read preference mode.

Examples

Example #1 MongoCommandCursor::setReadPreference tag set array syntax example


<?php

$m = new MongoClient('mongodb://rs1.example.com:27017', array('replicaSet' => 'myReplSetName'));
$collection = $m->selectCollection('test', 'people');

$cursor = $collection->aggregateCursor( [
    [ '$group' => [ '_id' => '$name', 'points' => [ '$sum' => '$points' ] ] ],
    [ '$sort' => [ 'points' => -1 ] ],
] );

// Prefer the nearest server in the "east" data center also used for reporting,
// but fall back to a server in the "west" data center
$cursor->setReadPreference(MongoClient::RP_NEAREST, [
    [ 'dc' => 'east', 'use' => 'reporting' ],
    [ 'dc' => 'west' ],
] );

foreach ($cursor as $person) {
    // ...
}

// If the read preference is changed, it will be used the next time the cursor
// is rewound and the command is re-executed.
$cursor->setReadPreference(MongoClient::RP_PRIMARY);

foreach ($cursor as $person) {
    // ...
}

?>