[HIVE-21544] Constant propagation corrupts coalesce/case/when expressions during folding

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-alpha-1
• Assignee: Zoltan Haindrich
• Reporter: Zoltan Haindrich
• Created: 29/Mar/19 15:06
• Updated: 27/Feb/24 22:23
• Resolved: 30/Mar/19 01:27

Description

set hive.fetch.task.conversion=none;
set hive.optimize.ppd=false;

create table t (s1 string,s2 string);

insert into t values (null,null);

explain
select
        coalesce(s1, 'null_value' ), coalesce(s2, 'null_value' ),
        coalesce(s1, 'null_value' )=coalesce(s2, 'null_value' ),
        case when coalesce(s1, 'null_value' )=coalesce(s2, 'null_value' ) then 'eq' else 'noteq' end
from t;

select
        coalesce(s1, 'null_value' ), coalesce(s2, 'null_value' ),
        coalesce(s1, 'null_value' )=coalesce(s2, 'null_value' ),
        case when coalesce(s1, 'null_value' )=coalesce(s2, 'null_value' ) then 'eq' else 'noteq' end
from t;

incorrect result is:

null_value      null_value      NULL    noteq

expected result:

null_value     null_value      true    eq