[CALCITE-4208] Improve metadata row count for Join

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.26.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Ruben Q L
• Reporter: Ruben Q L
• Created: 01/Sep/20 15:29
• Updated: 06/Oct/20 17:16
• Resolved: 05/Sep/20 09:35

Description

Currently, the default metadata row count for join RelMdRowCount#getRowCount(Join rel, RelMetadataQuery mq) relies on RelMdUtil.getJoinRowCount. This method has several issues:

• In case of ANTI join, it returns the same estimation as a SEMI join
• In other cases (INNER, LEFT, RIGHT, FULL), it returns always the same formula:
  leftRowCount * rightRowCount * mq.getSelectivity(join, condition)
  which seems valid for an INNER join, but not for LEFT / RIGHT / FULL.

Issue Links

• links to: GitHub Pull Request #2131