How can we test expressions in hive

Question

How to test simple expressions in hive? I mean is there any dual table in hive like Oracle for testing expression and functions Or we have to create sample tables with few records everytime to test any expression . I was looking for any dual table in hive. Does hive have it?

Answer 1

Unfortunately, there is no dual table in hive. You will have to unit test your custom code on the actual data set or you can always create a subset of your data and run unit tests of custom codes on derived data sets.

Answer 2

In late Hive, you can directly write query without "from table", such as 1. select 1 2. select UNIX_TIMESTAMP()

If you need to apply your function on some data, you can create a dual table using create table as select value.

You can try the query here http://demo.gethue.com/

Answer 3

I don't think you need dual table, Single-row SELECT statements do not require a FROM clause. For example:select instr('CricketSports',' ') returns

Co 0

Answer 4

To create a dual like table in hive where there is one column and one row you can do the following:

create table dual (x int);
insert into table dual select count(*)+1 as x from dual;

Describe the table:

describe dual;
col_name  data_type
x         int

Query contents:

select * from dual;
dual.x
1

Use to test expressions:

select split('3,2,1','\\,') as my_new_array from dual;

Output:

["3","2","1"]

I have used this table to test many expressions in hive successfully.