title: Return number of documents based on words in a field's string
body: <p>How can I return the number of documents that have more than 2 elements in the "words" list with more than 3 words in "word_combination". 
  Is there a way to count the number of words in a string? </p>
  
  <p>Example: return document if (the length of "words" > 2) AND ("words.word_combination" has more than 3 words) </p>
  
  <p>I have many documents stored. One document's structure looks like this:</p>
  
  <pre><code>"_source" : {
  "group_words" : [
  
    {
      "amount" : 1140,
      "words" : [
        {
          "relevance_score" : 56,
          "points" : 66461,
          "bits" : 100,
          "word_combination" : "cat dog"
        },
        {
          "relevance_score" : 84,
          "points" : 45202,
          "bits" : 990,
          "word_combination" : "cat dog elephant"
        },
        {
          "relevance_score" : 99,
          "points" : 30974,
          "bits" : 70,
          "word_combination" : "elephant cat mouse leopard"
        }
      ],
      "group" : "whatever"
    },
    {
      "amount" : 1320,
      "words" : [
        {
          "relevance_score" : 25,
          "points" : 53396,
          "bits" : 70,
          "word_combination" : "lion elephant"
        },
        {
          "relevance_score" : 66,
          "points" : 52166,
          "bits" : 20,
          "word_combination" : "lion mouse fish cat dog"
        },
        {
          "relevance_score" : 82,
          "points" : 49316,
          "bits" : 810,
          "word_combination" : "elephant cat mouse leopard dog lion"
        },
        {
          "relevance_score" : 87,
          "points" : 127705,
          "bits" : 290,
          "word_combination" : "elephant cat mouse leopard tiger lion"
        }
      ],
      "group" : "whatever"
    },
    {
      "amount" : 11260,
      "words" : [
        {
          "relevance_score" : 0,
          "points" : 37909,
          "bits" : 9000,
          "word_combination" : "elephant cat mouse leopard tiger lion monkey"
        },
        {
          "relevance_score" : 3,
          "points" : 35782,
          "bits" : 540,
          "word_combination" : "elephant"
        }
      ],
      "group" : "whatever"
    }      
  ]
  </code></pre>
  
  <p>}</p>