title: Elastic Search 6.0 from/size not work, get duplicate
body: <p>I'm new to Elastic search. I'm trying to get all the data between a time window. The result size is 10 by default. Is there any way to get all data with multiple query or within one query?</p>
  
  <p>This is the query I use</p>
  
  <pre><code>query={
    "from" : 0,
    "size" : 30,
    "query":{
      "range":{
       "created_at":{
            "gte":"2010-01-27T02:47:19",
            "lte":"2010-01-27T23:16:59",
            "format": "yyyy-MM-dd'T'HH:mm:ss"
       }
      }
    }
  }
  </code></pre>
  
  <p>As the result data must be larger than 30. I think using from to multiple query data.
  After the first time search, I will do a second one, like this:</p>
  
  <pre><code>query={
    "from" : 1,
    "size" : 30,
    "query":{
      "range":{
       "created_at":{
            "gte":"2010-01-27T02:47:19",
            "lte":"2010-01-27T23:16:59",
            "format": "yyyy-MM-dd'T'HH:mm:ss"
       }
      }
    }
  }
  </code></pre>
  
  <p>But this doesn't work. The response from the second query return all almost the same data as the first one.</p>
  
  <p>Could anyone tell me what's the problem?</p>
  
  <p>I'm using ElasticSearch Python lib.</p>
  
  <p>Thanks</p>