title: Filtering query in elastic search for nested model
body: <p>I am new to elastic search and I have to do filter based on following condition.</p>
  
  <p>Filter: </p>
  
  <pre><code>FirstName : 
  Abc
  noName
  </code></pre>
  
  <p>My schema looks like below:</p>
  
  <pre><code>{  
     Id:123,
     Name:{  
        FirstName:"abc",
        LastName:"xyz"
     }
  },
  {  
     Id:1234
  },
  {  
     Id:1235,
     Name:{  
        FirstName:"yuiy",
        LastName:"poi"
     }
  }
  </code></pre>
  
  <p>Some of mine data has Name model added but some of them does not. And I want to filter a data based on FirstName should be "Abc" or Name Field should not exist.</p>
  
  <p>So if i filter using above filter criteria it should give me 123 and 1234 Ids document result.</p>
  
  <p>So how Can I write elastic search query for this? I am connecting using Nest with Asp.Net Mvc.</p>
  
  <p>So if someone can provide me Nest query or Elastic Search query that would be helpful.</p>