PERF: reindex with MultiIndex

[lukemanley]

• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added an entry in the latest doc/source/whatsnew/v1.5.0.rst file if fixing a bug or adding a new feature.

Avoid unnecessary (and potentially expensive) call to MultiIndex._values. This only matters when MultiIndex._values has not been cached. Existing asv has been updated to test cached and non-cached cases.

import numpy as np
import pandas as pd

mi = pd.MultiIndex.from_arrays(
  [np.arange(10**6)] * 2
)
mi2 = pd.MultiIndex.from_arrays(
  [np.arange(10**7)] * 2
)

df = pd.DataFrame({"A": 1.0}, index=mi)

%timeit x = df.reindex(mi2.copy())

1.84 s ± 106 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)   <- main
685 ms ± 22.3 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)  <- PR

[jbrockmendel]

nice!

[jreback]

very nice @lukemanley

[twoertwein]

I think this PR made pyright unhappy, but I honestly don't see how this PR affected _mixins.py:

pandas/core/arrays/_mixins.py:185:26 - warning: Instance methods should take a "self" parameter (reportSelfClsParameterName)

If the solution is to ignore this warning, you can add
# pyright: reportSelfClsParameterName = false
at the top of the file.

edit:
or rename cls to self:

pandas/pandas/core/arrays/_mixins.py

Line 185 in 3e718e3

def _from_factorized(cls, values, original):

[jreback]

i think was a prior PR

[twoertwein]

i think was a prior PR

Yes, you are right: #46214 If no one beats me, I will create a PR to rename cls to self