[Kernel] Support column mapping mode in REPLACE TABLE including with fieldId re-use #4518
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allisonport-db
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vkorukanti
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May 12, 2025
amogh-jahagirdar
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May 13, 2025
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Which Delta project/connector is this regarding?
Description
PR#1 here #4520 separates some of this out.
This PR re-enables support for column mapping tables with REPLACE, and allows fieldId re-use when the type/nullability is compatible. To check for this compatibility we essentially re-use our schema evolution code. Valid schema transformations in the normal case should also be valid changes when reusing fieldIds across REPLACE. Any fields in the replaceSchema that are not reusing existing fieldIds will be treated as new fields during the schema evolution validation.
This validation checks that nullability changes are valid (cannot change from nullable to non-nullable) and that type changes are valid (for now, cannot change types). Columns are able to be moved (or nested columns dropped) if the other invariants hold.
Note, this currently restricts REPLACE to operations that maintain the same column mapping mode. In the future, we will loosen this restriction but for now this lessens the scope of this PR.
How was this patch tested?
Adds unit tests.