title: RavenDB Faceted Search: how to build fecets on category specific attributes
body: <p>I have product documents with two types of attributes. General attributes that applies for each product and category specific attributes which vary  by each product category.</p>
  
  <pre><code>{
    // Product general attributes
    "Title": "",
    "Brand": "",
    "Category",
    ...,
  
    // Category specific attributes
    "Attributes": [
      {
        "Name": "",
        "Value": ""
      },
      {
        "Name": "",
        "Value": ""
      },
      {
        "Name": "",
        "Value": ""
      },
      ...
    ]
  }
  </code></pre>
  
  <p>The names in 'Attributes' array are all different.</p>
  
  <p>My question is how can I build facets on attribute names of category specific attributes? </p>