[HIVE-23194] Use Queue Instead of List for CollectOperator

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 4.0.0-alpha-1
• Target Version/s: 4.0.0
• Assignee: David Mollitor
• Reporter: David Mollitor
• Created: 13/Apr/20 23:48
• Updated: 17/Nov/22 08:50
• Resolved: 18/Apr/20 03:49

Description

https://github.com/apache/hive/blob/d6948a28ab3e34e5116591a60a96bdf031185e47/ql/src/java/org/apache/hadoop/hive/ql/exec/CollectOperator.java#L85-L88

CollectOperator.java

   rowList = new ArrayList<Object>();
...
    } else {
      result.o = rowList.remove(0);
      result.oi = standardRowInspector;
    }

Removing from the head of an ArrayList is an expensive operation because it needs to shift all of the elements down in the array for each call. Better to use a Queue