The previous DataSourceFunction inherited from RichSourceFunction.
As a result, no matter how much the parallelism of flink is set, the parallelism of DataSourceFunction is only 1.
Now modify it to RichParallelSourceFunction.
And when flink has multiple degrees of parallelism, assign the doris data to each parallelism.
For example, read dorisPartitions.size = 10, flink.parallelism = 4
The task is split as follows:
task0: dorisPartitions[0],[4],[8]
task1: dorisPartitions[1],[5],[9]
task2: dorisPartitions[2],[6]
task3: dorisPartitions[3],[7]
549e849400