BUG: Fix metadata mutation in Index set operations (intersection/unio… #63174
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rhshadrach
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Dec 7, 2025
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Looking good, would like a 2nd eye on this. cc @jbrockmendel
pandas/tests/indexes/test_setops.py
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| class TestSetOpsMutation: |
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We'd like to move away from having test classes in cases where the class itself isn't useful. Can you just make these functions.
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Got it. I'll convert them to functions shortly.
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…n) (#63169)
doc/source/whatsnew/vX.X.X.rstfile if fixing a bug or adding a new feature.AGENTS.md.Previously,
Index.intersectionandIndex.union(includingMultiIndeximplementations) would return a direct reference toself(orother) if the result was identical to the input. This allowed side effects where mutating the metadata (e.g..name) of the result would corrupt the original index.This change forces a shallow copy (
deep=False) in these cases. This preserves the performance benefit of sharing the underlying data array while ensuring the Index container itself is a distinct object with independent metadata.