[IMPALA-7497] Consider reintroducing numNulls count in compute stats

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 3.0, Impala 2.12.0, Impala 3.1.0
• Fix Version/s: Impala 3.2.0
• Component/s: Frontend
• Epic Color: ghx-label-3
• Assignee: Bharath Vissapragada
• Reporter: Balazs Jeszenszky
• Created: 28/Aug/18 08:35
• Updated: 16/Feb/19 08:26
• Resolved: 08/Dec/18 01:10

Description

IMPALA-1003 disabled numNulls calculations for performance reasons. A lot has changed since, it'd be good to reevaluate computing numNulls. The planner still has some code that uses it for cardinality estimations, so just adding it back to compute stats can lead to easy wins.

Issue Links

• duplicates: IMPALA-7659 Collect count of nulls when collecting stats