title: Flink 1.4 Column 'rowtime' not found in any table
body: <p>I am following the documentation to <a href="https://ci.apache.org/projects/flink/flink-docs-release-1.4/dev/table/sourceSinks.html#configure-a-rowtime-attribute" rel="nofollow noreferrer">configure a TableSource with a rowtime attribute</a>. </p>
  
  <p>I register the <code>timestamp</code> field as follows</p>
  
  <pre><code>KafkaTableSource source = Kafka08JsonTableSource.builder()// set Kafka topic
              .forTopic("alerting")
              // set Kafka consumer properties
              .withKafkaProperties(getKafkaProperties())
              // set Table schema
              .withSchema(TableSchema.builder()
                      .field("tenant", Types.STRING())
                      .field("message", Types.STRING())
                      .field("frequency", Types.LONG())
                      .field("timestamp", Types.SQL_TIMESTAMP()).build())
              .failOnMissingField(true)
              .withRowtimeAttribute(
                      // "timestamp" is rowtime attribute
                      "timestamp",
                      // value of "timestamp" is extracted from existing field with same name
                      new ExistingField("timestamp"),
                      // values of "timestamp" are at most out-of-order by 30 seconds
                      new BoundedOutOfOrderTimestamps(TimeUnit.DAYS.toMillis(1)))
              .build();
  
      //register the alerting topic as kafka
      tEnv.registerTableSource("kafka", source);
  
      Table results = tEnv.sqlQuery("SELECT tenant, message, SUM(frequency) " +
              "FROM kafka " +
              "GROUP BY HOP(rowtime, INTERVAL '1' SECOND, INTERVAL '5' SECOND), tenant, message");
  
      tEnv.toAppendStream(results, Row.class).print();
  </code></pre>
  
  <p>and get the following error:</p>
  
  <blockquote>
    <p>Exception in thread "main" org.apache.flink.table.api.ValidationException: SQL validation failed. From line 1, column 64 to line 1, column 70: Column 'rowtime' not found in any table
        at org.apache.flink.table.calcite.FlinkPlannerImpl.validate(FlinkPlannerImpl.scala:93)
        at org.apache.flink.table.api.TableEnvironment.sqlQuery(TableEnvironment.scala:561)
        at oracle.flink.demo.KafkaSQLStream.main(KafkaSQLStream.java:62)
    Caused by: org.apache.calcite.runtime.CalciteContextException: From line 1, column 64 to line 1, column 70: Column 'rowtime' not found in any table
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
        at org.apache.calcite.runtime.Resources$ExInstWithCause.ex(Resources.java:463)</p>
  </blockquote>