Auto update not working in elasticsearch with Mysql

Question

I am having problem with Elasticsearch-jdbc river data automatically updates if anything updated in Mysql. Here is my Elastic Code

{
    "type" : "jdbc",
    "jdbc": {
    "driver" : "com.mysql.jdbc.Driver",
    "url" : "jdbc:mysql://localhost:3306/Dbname",
    "user" : "user",
    "password" : "password",
      "sql": "select id, firstname, lastname from mytable",                  
      "poll" : "6s",
      "strategy": "simple",
      "scale": 0,
      "autocommit": true,
      "bulk_size": 5000,
      "max_bulk_requests": 30,
      "bulk_flush_interval": "5s",
      "fetchsize": 100,
      "max_rows": 149669,
      "max_retries": 3,
      "max_retries_wait": "10s",
      "locale": "in",
      "digesting": true
    }
}

When i insert a new row or updates any data, it is not getting reflected in elastic. It always show the first time indexed data. Is there anything missing from my end. Please Advise.

Thanks