title: How to add an enum value to an AVRO schema in a FULL compatible way?
body: <p>I have an enum in an AVRO schema like this :</p>
  <pre><code>{
      &quot;type&quot;: &quot;record&quot;,
      &quot;name&quot;: &quot;MySchema&quot;,
      &quot;namespace&quot;: &quot;com.company&quot;,
      &quot;fields&quot;: [
          {
              &quot;name&quot;: &quot;color&quot;,
              &quot;type&quot;: {
                  &quot;type&quot;: &quot;enum&quot;,
                  &quot;name&quot;: &quot;Color&quot;,
                  &quot;symbols&quot;: [
                      &quot;UNKNOWN&quot;,
                      &quot;GREEN&quot;,
                      &quot;RED&quot;
                  ]
              },
              &quot;default&quot;: &quot;UNKNOWN&quot;
          }
      ]
  }
  </code></pre>
  <p>When using FULL (which means BACKWARD and FORWARD) compatibility mode, how am I supposed to add a new symbol to the enum ? Is this impossible ?</p>
  <p>I read <a href="https://stackoverflow.com/questions/60567697/avro-schema-is-adding-an-enum-value-to-existing-schema-backward-compatible">Avro schema : is adding an enum value to existing schema backward compatible?</a> but it doesn't help.</p>
  <p>Whenever I try to add a new value to the symbols it fails the compatibility check in the schema registry even though I have a default value on the enum. After testing a bit it seems that adding a new value is BACKWARD compatible but not FORWARD compatible. However, due to the default value I set I expected it to be also FORWARD compatible. Indeed the old reader schema should be able to read a value written by the new schema and default to the &quot;UNKNOWN&quot; enum value when it doesn't know the new symbol.</p>