"ts","dur","part","a","b"
100,150,1,111,444
250,50,1,111,"[NULL]"
300,100,1,111,555
400,100,1,111,666
500,50,1,222,666
600,50,1,333,666
650,50,1,333,"[NULL]"
500,100,3,444,"[NULL]"
100,100,4,555,"[NULL]"
200,50,4,666,999
250,50,4,777,"[NULL]"
100,25,5,888,"[NULL]"
125,50,5,888,1111
175,15,5,888,"[NULL]"
190,10,5,888,2222