[SPARK-22164] support histogram in estimating the cardinality of aggregate (or group-by) operator

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 2.2.0
• Component/s: SQL
• Assignee: Unassigned
• Reporter: Ron Hu
• Created: 29/Sep/17 00:37
• Updated: 12/Oct/17 15:21
• Resolved: 12/Oct/17 15:13

Description

Histogram is effective in dealing with skewed distribution. After we generate histogram information for column statistics, we need to adjust aggregate (or group-by) cardinality estimation based on equi-height histogram information.