[SPARK-31689] ShuffleBlockFetchIterator keeps localBlocks in its memory even though it never uses it

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Incomplete
• Affects Version/s: 2.4.5
• Component/s: Shuffle, Spark Core
• Assignee: Unassigned
• Reporter: Chandni Singh
• Created: 12/May/20 17:52
• Updated: 02/Jun/21 22:17
• Resolved: 02/Jun/21 22:17

Description

The localBlocks is created and used in the initialize method of ShuffleBlockFetchIterator but is never used after that. 
It can be local to the initialize method instead of being a field in the ShuffleBlockFetchIterator instance. It holds on to memory until iterator instance is alive which is unnecessary.