title: Confluent kafka connect elasticsearch document ID creation
body: <p>I am using confluent for to connect my DB and ES getting exception as: </p>
  
  <pre><code>org.apache.kafka.connect.errors.DataException: STRUCT is not supported as the document id.
      at io.confluent.connect.elasticsearch.DataConverter.convertKey(DataConverter.java:75)
      at io.confluent.connect.elasticsearch.DataConverter.convertRecord(DataConverter.java:84)
      at io.confluent.connect.elasticsearch.ElasticsearchWriter.write(ElasticsearchWriter.java:210)
      at io.confluent.connect.elasticsearch.ElasticsearchSinkTask.put(ElasticsearchSinkTask.java:119)
      at org.apache.kafka.connect.runtime.WorkerSinkTask.deliverMessages(WorkerSinkTask.java:429)
      at org.apache.kafka.connect.runtime.WorkerSinkTask.poll(WorkerSinkTask.java:250)
      at org.apache.kafka.connect.runtime.WorkerSinkTask.iteration(WorkerSinkTask.java:179)
      at org.apache.kafka.connect.runtime.WorkerSinkTask.execute(WorkerSinkTask.java:148)
      at org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:139)
      at org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:182)
      at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
      at java.util.concurrent.FutureTask.run(FutureTask.java:266)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
      at java.lang.Thread.run(Thread.java:745)
  </code></pre>
  
  <p><strong>My configuration in kafka-connect-JDBC is:</strong>.</p>
  
  <pre><code>name=task-view-list-stage
  connector.class=io.confluent.connect.jdbc.JdbcSourceConnector
  tasks.max=10 
  connection.url=jdbc:postgresql://localhost:5432/postgres?user=postgres&amp;password=test
  table.types=TABLE
  query=select * from employee_master
  mode=timestamp+incrementing
  incrementing.column.name=employee_master_id
  timestamp.column.name=modified_date
  validate.non.null=false
  topic.prefix=my-id-app
  </code></pre>
  
  <p><strong>And my kafka-connect Elasticsearch configuration is:</strong></p>
  
  <pre><code>name=es-id-view
  connector.class=io.confluent.connect.elasticsearch.ElasticsearchSinkConnector
  tasks.max=1
  topics=my-id-app
  topics.key.ignore=false
  transforms=InsertKey
  transforms.InsertKey.type=org.apache.kafka.connect.transforms.ValueToKey
  transforms.InsertKey.fields=employee_master_id
  connection.url=http://localhost:9200
  type.name=type_id
  </code></pre>
  
  <p>My Table structure is: </p>
  
  <pre><code>employee_master_id | emp_name | modified_date
  -----------------------------------------------------------
  1                  |  Bala    |  "2017-05-18 11:51:46.721182+05:30"
  -------------------------------------------------------------------
  2                  |  murugan | "2017-05-21 15:59:11.443901+05:30"
  -------------------------------------------------------------------
  </code></pre>
  
  <p>Please help me to resolve this issue</p>