title: PostgreSQL and Kafka Connect integration issue
body: <p>I am testing JDBC Sink connector to dump records from Kafka to PostgreSQL. Here is the Connector config:</p>
  
  <pre><code>{
      "name": "jdbc-sink-postgresql-1",
      "config": {
          "connector.class": "io.confluent.connect.jdbc.JdbcSinkConnector",
          "tasks.max": "1",
          "topics": "role",
          "connection.url": "jdbc:postgresql://localhost:5432/postgres?user=&amp;password=",
          "auto.create": "false",                                                   
          "insert.mode": "upsert",
          "mode":"incrementing",
          "table.name.format":"role",
          "pk.mode":"record_value",
          "pk.fields":"role_id"
      }
  }
  </code></pre>
  
  <p>When I run the connector, I am getting below exception:</p>
  
  <pre><code>java.sql.BatchUpdateException: Batch entry 1 INSERT INTO "role" ("role_id","role_name") VALUES (123,'admin') ON CONFLICT ("role_id") DO UPDATE SET "role_name"=EXCLUDED."role_name" was aborted.  
     Call getNextException to see the cause.
     at org.postgresql.jdbc2.AbstractJdbc2Statement$BatchResultHandler.handleError(AbstractJdbc2Statement.java:2778))
  </code></pre>
  
  <p>Any pointers as to what am I missing here? Please let me know if more information is needed.</p>