OnlyColumn Process
Keep selected columns and discard the rest
name
income
age
John
50,000
25
Marry
60,000
30
Peter
100,000
45
Donald
80,000
40
->pipe(new OnlyColumn(array( "age", "income" )))
age
income
25
50,000
30
60,000
45
100,000
40
80,000