[CALCITE-1635] Add MinRowCount metadata

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.12.0
• Assignee: Julian Hyde
• Reporter: Julian Hyde
• Created: 14/Feb/17 22:16
• Updated: 24/Mar/17 03:20
• Resolved: 15/Feb/17 17:40

Description

Add MinRowCount metadata, that describes that a RelNode will never return fewer than N rows.

The GROUP BY () operation has a peculiar effect if its input is empty: it increases the number of rows to 1. So, it is useful to know that a RelNode can never be empty, and a MinRowCount of 1 or higher communicates that.