[HIVE-27830] Deprecate hive.cbo.enable property

• Type: Task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Stamatis Zampetakis
• Reporter: Stamatis Zampetakis
• Created: 30/Oct/23 13:18
• Updated: 1 week ago 16:06

Description

CBO was enabled by default in Hive 1.1.0 (HIVE-8395) back in 2014. Since then the CBO planner has matured a lot and most production environments are running with this flag always on.

Nowadays, disabling CBO is strongly discouraged not only for performance reasons but also because various features depend on it.

Moreover, the vast majority of testing is done using CBO on and there is not much test coverage for the legacy code path.

It is impossible to fully support all Hive features using both CBO on/off and keeping this flag around significantly increases maintenance cost.

The goal of this ticket is to deprecate hive.cbo.enable property and inform users that its use is discouraged and unsupported. This would allow us to remove this property in a subsequent release.

Ideally we should emit an informative warning message when we detect that hive.cbo.enable is set to false.

Issue Links

• is related to: HIVE-28595 Not able to insert data with hive.cbo.enable=false
• is related to: HIVE-28674 MV creation having partition on clause fails when cbo is false
• is related to: HIVE-27831 Set hive.cbo.fallback.strategy to NEVER by default
• relates to: HIVE-8395 CBO: enable by default