title: RestHighlevelClient Sliced Scroll not working
body: <p>I am trying to fetch a large data records from Elasticsearch (Version - 6.4.2) in a minimal time.
  To do that, I am using multi threading to run each slice scroll in a separate thread.</p>
  
  <p>example: My query has 3 slices, so:</p>
  
  <pre><code>thread 1 - slice id 0
  thread 2 - slice id 1
  thread 3 - slice id 2
  </code></pre>
  
  <p>But while trying to get the results from slice id 1 and 2 it's returning 0 hits.</p>
  
  <p>I am trying <code>RestHighLevelClient#search()</code></p>
  
  <pre><code>public SearchResponse GetResponse(Integer sliceCount, Integer totalSlice, Integer searchSize, String[] identifiers ) throws IOException 
  {
  
      SliceBuilder sliceBuilder = new SliceBuilder(sliceCount, totalSlice);
      SearchSourceBuilder slicedSource = new SearchSourceBuilder().slice(sliceBuilder);
      slicedSource = slicedSource
          .query(QueryBuilders.boolQuery()
          .must(QueryBuilders.termsQuery("_id", identifiers)));
      return client.search(
        new SearchRequest()
          .indices("indexname")
          .types("type")
          .scroll("scrolltime")
          .source(slicedSource)
        );
  
  }
  </code></pre>