secondarysort
data:
20 21
50 51
50 52
50 53
50 54
60 51
60 53
60 52
60 56
60 57
70 58
60 61
70 54
70 55
70 56
70 57
70 58
10 55
80 67
90 43
30 44
50 67
50 87
40 77
20 11
10 55
20 84
70 45
90 55
91 44
78 44
76 32
88 23
91 34
56 11
33 23
24 11
参考： http://spark.apache.org/docs/2.0.1/api/python/pyspark.html#module-pyspark
