[CALCITE-5967] UnsupportedOperationException while implementing a call that requires a special collator

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.36.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Ruben Q L
• Reporter: Ruben Q L
• Created: 29/Aug/23 16:21
• Updated: 10/Nov/23 11:34
• Resolved: 06/Sep/23 08:53

Description

Regression introduced by a minor change within CALCITE-5914, detected while testing a downstream project with the latest Calcite main.

CALCITE-5914 (see 2a96512c) introduced this apparently innocuous change in RexImpTable#AbstractRexCallImplementor#unboxIfNecessary:

// old
argValueList.stream()
            .map(AbstractRexCallImplementor::unboxExpression)
            .collect(Collectors.toList());
=>
// new
Util.transform(argValueList,
            AbstractRexCallImplementor::unboxExpression);

Both expressions seem equivalent, however there is a subtle difference: the old one returns an ArrayList (where we can add new elements); whereas the new one returns a TransformingList that extends AbstractList and that does not support List#add.

After calling unboxIfNecessary, we might need to modify the argument list if we need a special collator to perform the operation:

    private ParameterExpression genValueStatement(...) {
      ...
      optimizedArgValueList = unboxIfNecessary(optimizedArgValueList);

      final Expression callValue =
          implementSafe(translator, call, optimizedArgValueList);
      ...
    }

    @Override Expression implementSafe(...) {
      ...
      final Expression fieldComparator =
          generateCollatorExpression(relDataType0.getCollation());
      if (fieldComparator != null) {
        argValueList.add(fieldComparator);  // <--- UnsupportedOperationException!
      }
      ...

Issue Links

• is caused by: CALCITE-5914 Cache compiled regular expressions in SQL function runtime
• is related to: CALCITE-3951 Support different string comparison based on SqlCollation
• links to: GitHub Pull Request #3403