[FLINK-16596] Support Enum-Values as part of a Key

• Type: Improvement
• Status: Open
• Priority: Not a Priority
• Resolution: Unresolved
• Component/s: API / DataStream
• Labels: auto-deprioritized-major auto-deprioritized-minor
• Assignee: Unassigned
• Reporter: Felix Wollschläger
• Created: 14/Mar/20 11:26
• Updated: 17/Nov/21 22:38

Description

See: FLINK-11774

Description:

The hashCode implementation of Enum-Values is guaranteed to be stable inside a JVM, but not accross multiple JVMs. This leads to failures when restoring from a checkpoint/savepoint containing Keyed-State on Keys with Enums as a part of the key.

For users of Flink there is a workaround to solve this problem:
Don't rely on the hashCode-Implementation of Enum-Values in the hashCode-Implementation of the actual key. Use the ordinal() or name().hashCode() instead of the Enum hashCode.

Goals of this improvement:

Implement a way to handle Enum-Values, by either handling Enum-Values on a internal level or implementing a abstract Base KeySelector class that users of flink can choose if their key contains a Enum-Value.

Code to reproduce a failure and first thoughts can be found in FLINK-11774 .

Issue Links

• is caused by: FLINK-11774 Unstable hashCode causes IllegalArgumentException in HeapPriorityQueueSet
• is related to: FLINK-16555 Preflight check for known unstable hashCodes.
• relates to: FLINK-5875 Use TypeComparator.hash() instead of Object.hashCode() for keying in DataStream API