Gabor Kaszab created IMPALA-8231:
------------------------------------
Summary: Impala allows ambiguous datetime patterns with
to_timestamp
Key: IMPALA-8231
URL: https://issues.apache.org/jira/browse/IMPALA-8231
Project: IMPALA
Issue Type: Bug
Components: Backend
Affects Versions: Impala 3.1.0
Reporter: Gabor Kaszab
Impala allows e.g. having multiple year sections in a datetime pattern.
{code:java}
select to_timestamp('2018-21-01-01', 'yyyy-yy-MM-dd');
+------------------------------------------------+
│······················
| to_timestamp('2018-21-01-01', 'yyyy-yy-mm-dd') |
│······················
+------------------------------------------------+
│······················
| 2021-01-01 00:00:00 |
│······················
+------------------------------------------------+
{code}
Here even the result is something weird:
{code:java}
select to_timestamp('21-2018-01-01', 'yy-yyyy-MM-dd');
+------------------------------------------------+
│······················
| to_timestamp('21-2018-01-01', 'yy-yyyy-mm-dd') |
│······················
+------------------------------------------------+
│······················
| 3918-01-01 00:00:00 |
│······················
+------------------------------------------------+
{code}
I think having the mentioned patterns in a from_timestamp() is fine as that
wouldn't make any inconsistencies in the result. However, in a to_timestamp()
it's ambiguous which section to use for populating e.g. the year part of a
timestamp. In that case I think returning an error is reasonable.
Oracle forbids the same:
{code:java}
select to_timestamp('2018-19-11-19', 'YYYY-YY-MM-DD') from DUAL;
ORA-01812: year may only be specified once
{code}
Note, that this issue is also true for any other datetime pattern element as
there is no duplicate or conflict check during parsing.
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