fix: Preserve metadata when a cross-join is swapped

[mkleen]

Which issue does this PR close?

• Relates to Join swap in join_selection flips schema-level metadata, failing "Schema mismatch" #23461 but resolves it only for cross-joins. The same problem exisists for Hash/NL joins. There will be follow-ups.

Rationale for this change

When a cross-join is swapped, the metadata is rebuilt based on the inverted inputs. This can cause a change of metadata when the metadata has conflicting values e.g.:

// left: 1000 rows, schema metadata {"key": "left"}
// right: 2 rows, schema metadata {"key": "right"}
// Cross join will swap the sides
ctx.sql("select * from left cross join right").await?.collect().await?;
// -> Internal error: ... 'join_selection' failed. Schema mismatch.
// Metadata should be {"key" : "right" } but changed to {"key" : "left" } 
// because of the swap of sides and the rebuilt of the metadata starting from the other direction.

The cross-join should preserve the original metdata when it's swapped.

What changes are included in this PR?

• This pr avoids rebuilding the metadata based on the swapped inputs and uses the original metadata instead
• Test

Are these changes tested?

Yes

Are there any user-facing changes?

No

[mkleen]

This rebuilds the schema in the same way as CrossJoinExec::new does and preserves the metadata.

[alamb]

I wonder if we can make a helper (as a follow on) to handle this logic rather than sprinkling the same fix through the code in many places 🤔

[mkleen]

Yes!

[mkleen]

Do you want the helper as part of this PR?

[alamb]

We can do it as a follow on PR perhaps

[alamb]

FYI @fangchenli

[alamb]

Makes sense to me -- thank you @mkleen

[alamb]

I wonder if we can make a helper (as a follow on) to handle this logic rather than sprinkling the same fix through the code in many places 🤔

[mkleen]

@alamb Thanks for the review!

[alamb]

Thanks @mkleen

[fangchenli]

Sorry, I didn't get a chance to look at it. Thanks for the PR @mkleen and thanks for the review @alamb

[2010YOUY01]

Do we have an end-to-end bug reproducer (SQL/query level)? This looks like a major bug, and I think the given UT can't guarantee the test goal, here is the reason: #23759 (comment)

I can help to look into it further.

[mkleen]

Do we have an end-to-end bug reproducer (SQL/query level)? This looks like a major bug, and I think the given UT can't guarantee the test goal, here is the reason: #23759 (comment)

I can help to look into it further.

@2010YOUY01 See #23857