[CALCITE-6474] Aggregate with constant key can get a RowCount greater than its MaxRowCount

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.37.0
• Fix Version/s: 1.38.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Ruben Q L
• Reporter: Ruben Q L
• Created: 16/Jul/24 16:21
• Updated: 17/Oct/24 22:41
• Resolved: 17/Oct/24 22:41

Description

An Aggregate with constant key can get a RowCount greater than its MaxRowCount.

The root cause is that this logic in RelMdMaxRowCount

// Aggregate with constant GROUP BY always returns 1 row
if (rel.getGroupType() == Aggregate.Group.SIMPLE) {
  final RelOptPredicateList predicateList =
    mq.getPulledUpPredicates(rel.getInput());
  if (!RelOptPredicateList.isEmpty(predicateList)
    && allGroupKeysAreConstant(rel, predicateList)) {
    return 1D;
  }
}

is not applied in RelMdRowCount.

Therefore we can get an Aggregate whose MaxRowCount is 1, but its RowCount is X (> 1).

Issue Links

• links to: GitHub Pull Request #3861