lib/Doctrine/MongoDB/Query/Builder.php
public function setReadPreference($readPreference, array $tags = null)
    {
        $this->query['readPreference'] = $readPreference;
        $this->query['readPreferenceTags'] = $tags;
        return $this;
    }
public function setReadPreference($readPreference, array $tags = null)
    {
        $this->query['readPreference'] = $readPreference;
        $this->query['readPreferenceTags'] = $tags;
        return $this;
    }
public function setReadPreference ( $ readPreference , array $ tags = null ) { $ this -> query [ 'readPreference' ] = $ readPreference ; $ this -> query [ 'readPreferenceTags' ] = $ tags ; return $ this ; }
Set the read preference for the query.

This is only relevant for read-only queries and commands.

@see http://docs.mongodb.org/manual/core/read-preference/
@param mixed $value
@param boolean $atomic
@return $this
Set the read preference for the query .