title: Search documents with highest fields
body: <p>I'm  trying to get all the documents with highest field value (+ conditional term filter)</p>
  
  <p>Given the Employees mapping</p>
  
  <pre><code>Name     Department     Salary
  ----------------------------
  Tomcat   Dev             100
  Bobcat   QA               90
  Beast    QA              100 
  Tom      Dev             100
  Bob      Dev              90
  </code></pre>
  
  <p>In SQL it would look like</p>
  
  <pre><code>select * from Employees  where Salary = select max(salary) from Employees 
  </code></pre>
  
  <p>expected output </p>
  
  <pre><code>Name     Department     Salary
  ----------------------------
  Tomcat   Dev             100
  Beast    QA              100 
  Tom      Dev             100
  </code></pre>
  
  <p>and </p>
  
  <pre><code>select * from Employees  where Salary = (select max(salary) from Employees where Department ='Dev'  )
  </code></pre>
  
  <p>expected output </p>
  
  <pre><code>Name     Department     Salary
  ----------------------------
  Tomcat   Dev             100
  Tom      Dev             100
  </code></pre>
  
  <p>Is it possible with Elasticsearch ?</p>