[SPARK-24871] Refactor Concat and MapConcat to avoid creating concatenator object for each row.

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.0
• Fix Version/s: 2.4.0
• Component/s: SQL
• Assignee: Takuya Ueshin
• Reporter: Takuya Ueshin
• Created: 20/Jul/18 03:50
• Updated: 20/Jul/18 12:09
• Resolved: 20/Jul/18 12:09

Description

Refactor Concat and MapConcat to:

• avoid creating concatenator object for each row.
• make Concat handle containsNull properly.
• make Concat shortcut if null child is found.

Issue Links

• links to: [Github] Pull Request #21824 (ueshin)