(PECL solr >= 0.9.2)
SolrInputDocument::merge — Merges one input document into another
Merges one input document into another.
The source document.
If this is TRUE it will replace matching fields in the destination document.
成功した場合に TRUE を、失敗した場合に FALSE を返します。 In the future, this will be modified to return the number of fields in the new document.