fix: cardinality returns incorrect results for ragged nested arrays

[lyne7-sc]

Which issue does this PR close?

• Closes cardinality returns incorrect results for ragged nested arrays #23270.

Rationale for this change

cardinality used compute_array_dims and multiplied the inferred dimensions to compute nested array cardinality. That only works for rectangular nested arrays, where every nested list has the same shape.

For ragged nested arrays, compute_array_dims follows the first nested value shape and can return dimensions that do not describe the actual number of leaf elements. As a result, cardinality can return incorrect results for valid nested arrays.

Examples:

select cardinality([[1], [2, 3]]);
-- before: 2
-- after:  3

select cardinality([[1, 2, 3], []]);
-- before: 6
-- after:  3

select cardinality([[], [1, 2]]);
-- before: 0
-- after:  2

What changes are included in this PR?

This PR changes list cardinality computation to recursively count actual leaf elements instead of multiplying inferred dimensions.

Are these changes tested?

Yes, added sqllogictest coverage.

Are there any user-facing changes?

Bug fix only.

Additional discussion

The root cause is that cardinality() used compute_array_dims() and multiplies the returned dimensions.

compute_array_dims() itself follows the first child array when computing nested dimensions. This behavior may also need a separate discussion for ragged nested arrays, because such arrays do not have a single rectangular dimension vector. For example, array_dims([[1], [2, 3]]) currently returns [2, 1].

[nuno-faria]

Thanks @lyne7-sc, LGTM.

For example, array_dims([[1], [2, 3]]) currently returns [2, 1].

Yeah array_dims does not make sense without fixed lengths. Maybe it could return an error in the future, like array_add:

> select array_add([1, 2], [3]);
Execution error: array_add requires both list inputs to have the same length per row, got 2 and 1 at row 0

[lyne7-sc]

Thanks @nuno-faria for the review!

Maybe it could return an error in the future

That makes sense