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我正在尝试将方解石与Kafka结合,我参考了CsvStreamableTable。将Kafka与Apache Calcite结合起来
每个ConsumerRecord是转换使用fowlloing代码为Object []:
static class ArrayRowConverter extends RowConverter<Object[]> {
private List<Schema.Field> fields;
public ArrayRowConverter(List<Schema.Field> fields) {
this.fields = fields;
}
@Override
Object[] convertRow(ConsumerRecord<String, GenericRecord> consumerRecord) {
Object[] objects = new Object[fields.size()+1];
int i = 0 ;
objects[i++] = consumerRecord.timestamp();
for(Schema.Field field : this.fields) {
Object obj = consumerRecord.value().get(field.name());
if(obj instanceof Utf8){
objects[i ++] = obj.toString();
}else {
objects[i ++] = obj;
}
}
return objects;
}
}
枚举被实现为以下中,一个线程是从卡夫卡不断地轮询记录,并把它们放入一个队列,getRecord()方法轮询从那个队列:
public E current() {
return current;
}
public boolean moveNext() {
for(;;) {
if(cancelFlag.get()) {
return false;
}
ConsumerRecord<String, GenericRecord> record = getRecord();
if(record == null) {
try {
Thread.sleep(200L);
} catch (InterruptedException e) {
e.printStackTrace();
}
continue;
}
current = rowConvert.convertRow(record);
return true;
}
}
我测试SELECT STREAM * FROM Kafka.clicks
,它工作正常。 rowtime是明确添加的第一列,值是卡夫卡的记录时间戳。
但当我
SELECT STREAM FLOOR(rowtime TO HOUR)
AS rowtime,ip,COUNT(*) AS c FROM KAFKA.clicks GROUP BY FLOOR(rowtime TO HOUR), ip
扔例外
java.sql.SQLException: Error while executing SQL "SELECT STREAM FLOOR(rowtime TO HOUR) AS rowtime,ip,COUNT(*) AS c FROM KAFKA.clicks GROUP BY FLOOR(rowtime TO HOUR), ip": From line 1, column 85 to line 1, column 119: Streaming aggregation requires at least one monotonic expression in GROUP BY clause
at org.apache.calcite.avatica.Helper.createException(Helper.java:56)
at org.apache.calcite.avatica.Helper.createException(Helper.java:41)
感谢朱利安,有没有简单的方法来声明列单调,还是应该像MockTable一样实现? – user2283216