lyne7-sc opened a new pull request, #23271:
URL: https://github.com/apache/datafusion/pull/23271
## Which issue does this PR close?
<!--
We generally require a GitHub issue to be filed for all bug fixes and
enhancements and this helps us generate change logs for our releases. You can
link an issue to this PR using the GitHub syntax. For example `Closes #123`
indicates that this PR will close issue #123.
-->
- Closes #23270.
## Rationale for this change
<!--
Why are you proposing this change? If this is already explained clearly in
the issue then this section is not needed.
Explaining clearly why changes are proposed helps reviewers understand your
changes and offer better suggestions for fixes.
-->
`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:
```sql
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?
<!--
There is no need to duplicate the description in the issue here but it is
sometimes worth providing a summary of the individual changes in this PR.
-->
This PR changes list cardinality computation to recursively count actual
leaf elements instead of multiplying inferred dimensions.
## Are these changes tested?
<!--
We typically require tests for all PRs in order to:
1. Prevent the code from being accidentally broken by subsequent changes
2. Serve as another way to document the expected behavior of the code
If tests are not included in your PR, please explain why (for example, are
they covered by existing tests)?
-->
Yes, added sqllogictest coverage.
## Are there any user-facing changes?
<!--
If there are user-facing changes then we may require documentation to be
updated before approving the PR.
-->
<!--
If there are any breaking changes to public APIs, please add the `api
change` label.
-->
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 may also be worth discussing for ragged nested arrays,
because `array_dims([[1], [2, 3]])` currently returns `[2, 1]`.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
