Elasticsearch not showing all the records(docs) from Cassandra NoSQL DB

Hi ,
I am having around 1 million records in Cassandra(2.1.13), But not all(limited number) of records are displayed in Elasticsearch(1.4.5) & Kibana after creating the index. We are using River plugin & cassandra-elasticsearch mapper.
I am wondering do i need to increase/change any setting in Elasticsearch.yml file?