[FLINK-24924] TO_TIMESTAMP and TO_DATE should fail

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: Table SQL / Planner
• Assignee: Unassigned
• Reporter: Francesco Guardiani
• Created: 16/Nov/21 12:57
• Updated: 15/Dec/21 11:26

Description

In a similar fashion to what described https://issues.apache.org/jira/browse/FLINK-24385, TO_TIMESTAMP and TO_DATE should fail instead of returning null.

In particular for these two functions, a failure in parsing could lead to very unexpected behavior, for example it could lead to records with null rowtime.

We should change these functions to fail by default when parsing generates an error. We can let users handle errors by letting them use TRY_CAST for the same functionality:

-- This fails when input is invalid
TO_TIMESTAMP(input)

-- Behaves the same as above
CAST(input AS TIMESTAMP)

-- This returns null when input is invalid
TRY_CAST(input AS TIMESTAMP)