Php/docs/mongocommandcursor.setreadpreference
MongoCommandCursor::setReadPreference
(PECL mongo >=1.6.0)
MongoCommandCursor::setReadPreference — Set the read preference for this command
说明
public MongoCommandCursor::setReadPreference
( string $read_preference
[, array $tags
] ) : MongoCommandCursor
参数
read_preference
- The read preference mode:
MongoClient::RP_PRIMARY
,MongoClient::RP_PRIMARY_PREFERRED
,MongoClient::RP_SECONDARY
,MongoClient::RP_SECONDARY_PREFERRED
, orMongoClient::RP_NEAREST
. tags
- An array of zero or more tag sets, where each tag set is itself an array of criteria used to match tags on replica set members.
返回值
Returns this cursor.
错误/异常
Emits E_WARNING
if either parameter is invalid, or if one or more tag sets are provided with the MongoClient::RP_PRIMARY
read preference mode.
范例
Example #1 MongoCommandCursor::setReadPreference() tag set array syntax example
<?php$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) { // ...}?>
参见
- The read preferences documentation.
- MongoCommandCursor::getReadPreference() - Get the read preference for this command
- MongoCursorInterface::setReadPreference() - Set the read preference for this query