[SPARK-12077] Use more robust plan for single distinct aggregation

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.6.0
• Fix Version/s: 1.6.0
• Component/s: SQL
• Labels: release_notes releasenotes
• Assignee: Davies Liu
• Reporter: Davies Liu
• Created: 01/Dec/15 21:32
• Updated: 17/Dec/15 06:45
• Resolved: 02/Dec/15 04:18

Description

Use try to match the behavior for single distinct aggregation with Spark 1.5, but that's not scalable, we should be robust by default, have a flag to address performance regression for low cardinality aggregation.

Issue Links

• is duplicated by: SPARK-6006 Optimize count distinct in case of high cardinality columns
• links to: [Github] Pull Request #10075 (davies)