title: How to query item's metadata from Couchbase?
body: <p>I put some data to CouchBase 1.8.1,and get it successful.But I want to query its metadata,as expiration and att_reason(non-json or json).In some document,it list the metadata with json format,for example:</p>
  
  <pre><code>{
   "_id" : "contact_475",
   "_rev" : "1-AB9087AD0977F089",
   "_bin" : "...",
   "$flags" : 0,
   "$expiration" : 0,
   "name" : "Fred Bloggs",
  }
  </code></pre>
  
  <p>How can I query item's metadata?</p>