title: What is the significance of doc_count_error_upper_bound in elasticsearch and how can it be minimized?
body: <p>I am always getting a high value for an aggregation query in elasticsearch on the <code>doc_count_error_upper_bound</code> attribute. It's sometimes as high as 8000 or 9000 for a ES cluster having almost a billion documents indexed. I run the query on an index of about 5M doc and I get the value to be about 300 to 500.</p>
  
  <p>The question is how incorrect are my results (I am trying a top 20 count query based on the JSON below)</p>
  
  <pre><code>"aggs":{ "group_by_creator":{ "terms":{ "field":"creator" } } } }
  </code></pre>