PERF: avoid copy in concatenate_array_managers if reindex already copies #44559
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jorisvandenbossche
added
ArrayManager
Performance
pandas/core/internals/concat.py
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| assert concat_axis == 0 | ||
| arrays = list(itertools.chain.from_iterable([mgr.arrays for mgr in mgrs])) | ||
| if copy: | ||
| if copy and axis1_needs_copy_this: |
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might be cleaner (and avoid copies in corner cases) to do this up in the for loop right before mgrs.append(mgr)
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Thanks, good idea, and that also simplified it quite a bit
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lgtm @jbrockmendel comment could be addressed here |
jbrockmendel
reviewed
Dec 4, 2021
pandas/core/internals/concat.py
Outdated
| # reindex all arrays | ||
| mgrs = [] | ||
| for mgr, indexers in mgrs_indexers: | ||
| axis1_needs_copy = True |
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nitpick again: elsewhere in this file we do basically the same thing with made_copy = False
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@jbrockmendel #42797 added an unconditional copy, while if you reindex the arrays, you already are sure you have a copy.
This gives a 20% improvement on some of the merge benchmarks.