(PECL solr >= 0.9.2)
SolrInputDocument::merge — Merges one input document into another
Merges one input document into another.
sourceDocThe source document.
overwrite
If this is true it will replace matching fields in the destination document.
成功時(shí)返回 true， 或者在失敗時(shí)返回 false。 In the future, this will be modified to return the number of fields in the new document.