(PECL solr >= 0.9.2)
SolrInputDocument::setFieldBoost — Sets the index-time boost value for a field
$fieldName, float $fieldBoostValue): boolSets the index-time boost value for a field. This replaces the current boost value for this field.
fieldNameThe name of the field.
fieldBoostValueThe index time boost value.
成功时返回 true， 或者在失败时返回 false。