A rowtime attribute requires an EventTime time characteristic in stream environment. But is: ProcessingTime
Time Characteristic 要设置成 EventTime .
streamExecutionEnvironment.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);
A limit operation on unbounded tables is currently not supported.
unbounded tables 不能用orderby排序
就是说暂时还不支持流数据的排序
批数据是有限的 , 流数据则认为是无限的.
org.apache.flink.api.common.InvalidProgramException: Aggregating on field positions is only possible on tuple data types.
使用聚合数据的操作时 , 只能使用tuple类型的数据格式.
基本的聚合操作 : sum,min,max,aggregate
Aggregation field position is out of range.
聚合操作的参数超出范围了.
超出tuple的范围了 , 比如 tuple2 , 但 sum 参数传了 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 在很多场景下 , Lambda方式的类 , 会缺少类型信息 . 建议使用类定义的方式 . 别图方便了.