A rowtime attribute requires an EventTime time characteristic in stream environment. But is: ProcessingTime
Time Characteristic 要設置成 EventTime .
streamExecutionEnvironment.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);
A limit operation on unbounded tables is currently not supported.
unbounded tables 不能用orderby排序
就是說暫時還不支持流數據的排序
批數據是有限的 , 流數據則認為是無限的.
org.apache.flink.api.common.InvalidProgramException: Aggregating on field positions is only possible on tuple data types.
使用聚合數據的操作時 , 只能使用tuple類型的數據格式.
基本的聚合操作 : sum,min,max,aggregate
Aggregation field position is out of range.
聚合操作的參數超出范圍了.
超出tuple的范圍了 , 比如 tuple2 , 但 sum 參數傳了 3
In many cases lambda methods don't provide enough information for automatic type extraction when Java generics are involved. An easy workaround is to use an (anonymous) class instead that implements the 'org.apache.flink.api.common.functions.JoinFunction' interface. Otherwise the type has to be specified explicitly using type information.
大概意思就是 在很多場景下 , Lambda方式的類 , 會缺少類型信息 . 建議使用類定義的方式 . 別圖方便了.