[CALCITE-7574] RelDecorrelator.isFieldNotNullRecursive throws IndexOutOfBoundsException when decorrelating correlated scalar subquery with Aggregate

[libe8013]

Jira Link

CALCITE-7574

Changes Proposed

In RelDecorrelator.isFieldNotNullRecursive, the Aggregate branch used ImmutableBitSet.size() for bounds checking, which returns the bitset capacity (words.length * 64,
typically ≥ 64) rather than the actual number of group keys. When a field index corresponds to an aggregate result field (not a group field), the check was too lenient, causing
groupSet.asList().get(index) to call nth(index) which throws IndexOutOfBoundsException.

Changed groupSet.size() to agg.getGroupCount() (equivalent to groupSet.cardinality()), which correctly returns the number of group keys. Aggregate result fields now
correctly return false instead of throwing an exception.

Bug introduced by [CALCITE-6962].

Reproduction

SELECT t1.deptno, t1.total_sal,
  (SELECT COUNT(DISTINCT t2.total_sal) + 1
   FROM (SELECT deptno, SUM(sal) AS total_sal
         FROM emp WHERE deptno IS NOT NULL
         GROUP BY deptno) t2
   WHERE t2.deptno = t1.deptno
     AND t2.total_sal > t1.total_sal) AS rank_sal
FROM (SELECT deptno, SUM(sal) AS total_sal
      FROM emp WHERE deptno IS NOT NULL
      GROUP BY deptno) t1
ORDER BY t1.deptno, t1.total_sal DESC

[xiedeyantu]

The commit message should not contain "Fix", we also should keep the message same as PR title and JIRA title.

[libe8013]

@xiedeyantu Updated as requested. Commit message, PR title, and JIRA summary are now aligned. Also renamed the Fix section to Solution in the description for consistency. Thanks!

[xiedeyantu]

The commit message and PR title should using "[CALCITE-7574] xxx" at the beginning.

[libe8013]

@xiedeyantu Updated. JIRA summary, PR title, and commit message now all use the [CALCITE-7574] prefix as requested. Thanks for clarifying!

[mihaibudiu]

Since there are 2 approvals already I think you can squash the commits for merging

[libe8013]

@mihaibudiu Squashed the commits into a single clean commit as requested. Ready for merge. Thanks for the review!

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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