[HIVE-24040] Slightly odd behaviour with CHAR comparisons and string literals

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Unassigned
• Reporter: Tim Armstrong
• Created: 15/Aug/20 00:03
• Updated: 07/Oct/20 16:45

Description

If t is a char column, this statement behaves a bit strangely - since the RHS is a STRING, I would have expected it to behave consistently with other CHAR/STRING comparisons, where the CHAR column has its trailing spaces removed and the STRING does not have its trailing spaces removed.

select count(*) from ax where t = cast('a         ' as string);

Instead it seems to be treated the same as if it was a plain literal, interpreted as CHAR, i.e.

select count(*) from ax where t = 'a         ';

Here are some more experiments I did based on https://github.com/apache/hive/blob/master/ql/src/test/queries/clientpositive/in_typecheck_char.q that seem to show some inconsistencies.

-- Hive version 3.1.3000.7.2.1.0-287 r4e72e59f1c2a51a64e0ff37b14bd396cd4e97b98

create table ax(s char(1),t char(10));

insert into ax values ('a','a'),('a','a '),('b','bb');

-- varchar literal preserves trailing space
select count(*) from ax where t = cast('a         ' as varchar(50));
+------+
| _c0  |
+------+
| 0    |
+------+

-- explicit cast of literal to string removes trailing space
select count(*) from ax where t = cast('a         ' as string);
+------+
| _c0  |
+------+
| 2    |
+------+

-- other string expressions preserve trailing space
select count(*) from ax where t = concat('a', '         ');
+------+
| _c0  |
+------+
| 0    |
+------+

-- varchar col preserves trailing space
create table stringv as select cast('a  ' as varchar(50));
select count(*) from ax, stringv where t = `_c0`;
+------+
| _c0  |
+------+
| 0    |
+------+

-- string col preserves trailing space
create table stringa as select 'a  ';
select count(*) from ax, stringa where t = `_c0`;
+------+
| _c0  |
+------+
| 0    |
+------+

jcamachorodriguez kgyrtkirk

Issue Links

• is related to: IMPALA-1652 Fix CHAR datatype: Incorrect results with basic predicate on CHAR typed column.