histogram_numeric is a UDAF which should calculate the distribution of given records. But at the same time
it should generate a table that represents one category by one row. In this point we can regard this type of
UDF is a combination of UDAF and UDTF. For example the output of histogram_numeric looks like
hive> SELECT explode(histogram_numeric(val, 3)) AS x FROM test_table;
| x | y |
|---|---|
| -3.62 | 10 |
| -0.12 | 3 |
| 5.24 | 12 |
So you can realize this operation by combination with explode function. Since explode separate one line array
into multiple rows, histogram_numeric creates one row which includes multiple records such as
[{"x":-3.62,"y":10},{"x":-0.12,"y":3},{"x":5.24,"y":12}]
There is no way to do assemble multiple records and generate multiple rows at once in one UDF. So this is a way to do so. But I’m now searching better way. If you know, please let me know.
Thanks.