title: how to set mapping for _id in elasticsearch
body: <p>I am creating a new index 'collegedatabase' with type 'studenttable' and my id are like 123,1234,12345 etc;
  When I am trying to get record with id 1234 always it returning the record of 123 only.
  I have tried to set mapping for '_id' field as follows:</p>
  
  <pre><code>{
     "studenttable" : {
        "_id" : {
          "index" : "not_analyzed"
  
        }
     }
  }
  </code></pre>
  
  <p>Still it is showing same result.
  Can anyone please help me with this.
  I am using like this(It is from node.js)</p>
  
  <pre><code>client.search({
          index: 'collegedatabase',
          type: 'studenttable',
          id: req.body.sid
      },function(err,resp){ 
       .............
  });
  </code></pre>