Hi Ramin,
Thank you for working on this. It is a pity that we didn't fix this
earlier. Somehow, this behavior is a historical artifact from the Blink
merge. The current behavior is confusing and simply wrong. We should fix
issues that lead to data loss. Fortunately, the TIME type is not used
often, as most pipelines use TIMESTAMP types.
+1 for this breaking change, as it is a valid bug fix.
Thanks,
Timo
On 26.02.26 15:23, Ramin Gharib wrote:
Hi everyone,
I'd like to open a discussion regarding an issue we have where time
precision is not working properly, which requires some code updates to
resolve.
I am tracking this under the following Jira ticket [1].
When setting a column type to a specific precision, such as TIME(2), the
schema incorrectly registers it as TIME(0). Consequently, the returned
values suffer from data loss. For example, if a user runs the following:
- CREATE TABLE test_sql_time2 (val TIME(2));
- INSERT INTO test_sql_time2 VALUES (TIME '14:30:00.12');
Selecting the value returns 14:30:00 instead of the expected 14:30:00.12.
Furthermore, running DESCRIBE test_sql_time2; confirms that the Data Type
is incorrectly set to TIME(0).
To fix this, I have updated the code to ensure the time precision is
handled and maintained correctly. I have opened a pull request with the
implementation [2].
Please note that fixing this introduces a change in behavior. Because
precision will now be respected, existing pipelines that unknowingly relied
on the data being implicitly truncated to TIME(0) will start retaining
their fractional precision. I would like to get the community's thoughts on
whether we need to treat this as a formal breaking change, and if we should
consider any specific backward-compatibility or migration steps.
I would appreciate it if anyone interested could take a look at the
Jira/PR, review the proposed changes, and share any feedback or thoughts on
the approach.
Looking forward to hearing from you.
Best regards,
Ramin Gharib
[1] https://issues.apache.org/jira/browse/FLINK-17224
[2] https://github.com/apache/flink/pull/26954
