[PARQUET-42] Add HyperLogLog / CountMinSketch to parquet statistics

• Type: New Feature
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Component/s: parquet-mr
• Assignee: Unassigned
• Reporter: Alex Levenson
• Created: 24/Jul/14 06:30
• Updated: 25/Sep/20 17:45

Description

HLL and CMS for rowgroups could help with query planning (getting a sense of data skew) and with cheaply counting approximate distinct values. Both are commutative which means they can be combined across rowgroups (unlike an exact distinct count for example).