title: Possible to use complex object types as keys in maps in Avro?
body: <p>Is it possible to use non Strings as keys in a Map with Avro?</p>
  
  <p>I found this issue <a href="https://issues.apache.org/jira/browse/AVRO-680?focusedCommentId=16985083&amp;page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-16985083" rel="nofollow noreferrer">AVRO-680</a> which claims to have added non string key support, but I cannot find any examples, or work out from the patch how the new support works with a schema.</p>
  
  <p>I would like to do something like this:</p>
  
  <pre><code>    "name": "aThing",
      "type": "record",
      "fields": [
          { "name": "aMapOfThings", "type": {
               "type": "map", "keys": "MyKeyType", "values": "MyValueType"
             }
          }
      ]
  </code></pre>
  
  <p>Or in <code>avdl</code>:</p>
  
  <pre><code>  record aThing {
      map&lt;MyKeyType, MyValueType&gt; aMapOfThings = [:];
    }
  </code></pre>
  
  <p>Exactly like this question for protobuf: <a href="https://stackoverflow.com/questions/34729968/protobuf-objects-as-keys-in-maps">Protobuf objects as Keys in Maps</a></p>