How to concatenate the elemets of int array to str

问题:

I'm trying to concatenate the element of int array to one string in hive.

The function concat_ws works only for string arrays, so I tried cast(my_int_array as string) but it's not working.

Any suggestion?

回答1:

Try to transform using /bin/cat:

from mytable select transform(my_int_array) using '/bin/cat' as (my_int_array);

Second option is to alter table and replace delimiters:

1) ALTER TABLE mytable  CHANGE COLUMN my_int_array = my_int_array_string string;
2) SELECT REPLACE(my_int_array_string, '\002', ', ') FROM mytable;

回答2:

It seems that the easiest way is to write a custom UDF to perform this specific task:

public class ConcatIntArray extends UDF {
   public String evaluate(ArrayList<Integer> in, final String delimiter){
       return in.stream().map(u-> String.valueOf(u)).collect(Collectors.joining(delimiter));
   }
}