GH-49217: [C++][Parquet] Fix map type to preserve key-value metadata #49218
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Could you help review this? @pitrou @adamreeve @mapleFU |
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Hard to believe it doesn't have mapping...
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Thanks all for the review! |
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Rationale for this change
Previously, when converting Parquet schemas back to Arrow schemas with serialized ARROW:schema metadata, the key-value metadata on map nested fields (key/value fields) was lost. The GetNestedFactory() function lacked a MAP case, preventing ApplyOriginalStorageMetadata from recursively restoring metadata to map children. This fix adds MAP support to the factory function, enabling proper metadata preservation for maps during schema roundtrips.
What changes are included in this PR?
Added a MAP case to GetNestedFactory() that returns a lambda to reconstruct MapType while preserving the keys_sorted property from the original type.
Are these changes tested?
Yes. Added a test case to verify the issue has been fixed.
Are there any user-facing changes?
No.