[HIVE-20255] Review LevelOrderWalker.java

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.0.0, 4.0.0
• Fix Version/s: 4.0.0-alpha-1
• Component/s: Query Planning
• Flags: Patch
• Assignee: David Mollitor
• Reporter: David Mollitor
• Created: 27/Jul/18 16:35
• Updated: 17/Nov/22 08:54
• Resolved: 04/Feb/19 11:24

Description

https://github.com/apache/hive/blob/6d890faf22fd1ede3658a5eed097476eab3c67e9/ql/src/java/org/apache/hadoop/hive/ql/lib/LevelOrderWalker.java

• Make code more concise
• Fix some check style issues

      if (toWalk.get(index).getChildren() != null) {
        for(Node child : toWalk.get(index).getChildren()) {

Actually, the underlying implementation of getChildren() has to do some real work, so do not throw away the work after checking for null. Simply call once and store the results.