[CALCITE-5091] RelMdRowCount can return more accurate rowCount when fetch is deterministic and offset is dynamic

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.30.0
• Fix Version/s: 1.31.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Jiajun Xie
• Reporter: Jiajun Xie
• Created: 12/Apr/22 01:13
• Updated: 03/Aug/22 16:21
• Resolved: 24/Apr/22 01:50

Description

The sql from CALCITE-5048

select * from emp order by ename limit 1 offset ?

RelMdRowCount#getRowCount will return 14d, because it always return rowCount when offset is dynamic.

    if (rel.offset instanceof RexDynamicParam) {
      return rowCount;
    }

Obviously, rowCount will not exceed 1 because LIMIT 1. We can improve it.

Issue Links

• is related to: CALCITE-5048 Query with parameterized LIMIT and correlated sub-query throws AssertionError "not a literal"
• links to: GitHub Pull Request #2774