[IMPALA-7960] wrong results when comparing timestamp casted to varchar of smaller length to a string literal in a binary predicate

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: Impala 2.12.0
• Fix Version/s: Impala 3.2.0
• Labels: correctness
• Epic Color: ghx-label-9
• Assignee: Bikramjeet Vig
• Reporter: Bikramjeet Vig
• Created: 11/Dec/18 23:41
• Updated: 12/Dec/18 17:36
• Resolved: 12/Dec/18 17:36

Description

Expression rewriting seems to identify this as a redundant cast and removes it.

Steps to re-create:

select * from (select cast('2018-12-11 09:59:37' as timestamp) as ts) tbl where cast(ts as varchar(10)) = '2018-12-11';

output:

Fetched 0 row(s) 

Now disable expression re-writes.

set ENABLE_EXPR_REWRITES=false;
select * from (select cast('2018-12-11 09:59:37' as timestamp) as ts) tbl where cast(ts as varchar(10)) = '2018-12-11';

output:

+---------------------+
| ts                  |
+---------------------+
| 2018-12-11 09:59:37 |
+---------------------+

Issue Links

• relates to: IMPALA-5929 Remove useless explicit casts to string