[FLINK-17610] Align the behavior of result of internal map state to return empty iterator

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Done
• Affects Version/s: 1.11.0
• Fix Version/s: 1.11.0
• Component/s: Runtime / State Backends
• Labels: pull-request-available
• Assignee: Nicholas Jiang
• Reporter: Nicholas Jiang
• Created: 11/May/20 09:07
• Updated: 02/Jun/20 08:33
• Resolved: 28/May/20 09:49

Description

There are different behaviors of result of internal map state. For HeapMapState, #entries(), #keys(), #values(), and #iterator() would all return null. However, for RocksDBMapState, #entries() would return null, while #keys(), #values(), #iterator() would return empty iterator. UserFacingMapState would align these behaviors to empty iterator for users, therefore this should better align these internal behavior to return empty iterator instead of null.

Issue Links

• fixes: FLINK-17015 Fix NPE from NullAwareMapIterator
• is depended upon by: FLINK-17015 Fix NPE from NullAwareMapIterator
• links to: GitHub Pull Request #12078
• links to: GitHub Pull Request #12366