BUG: pd.concat fails when handling MultiIndex if repeated index exists

[charlesdong1991]

xref #20565

• tests added / passed
• passes black pandas
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[WillAyd]

Can you check benchmarks for this? I would think that replacing the internal factorize with itertools.chain could drastically slow things down

[charlesdong1991]

thanks! @WillAyd changed

btw, just a question, somehow, yesterday when i was trying to check benchmark, it takes ages and I felt my laptop almost burned, is this normal for local benchmark checking?

I will check the benchmark tomorrow

[WillAyd]

Running the entire benchmark suite will take a while. You probably want to limit it to what you think is the affected code, so something like asv continuous upstream/master HEAD -b join_merge.Concat for this PR

[pep8speaks]

Hello @charlesdong1991! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2020-04-13 09:00:15 UTC

[WillAyd]

@charlesdong1991 still active? Can you fix merge conflicts and try to get CI green?

[charlesdong1991]

yeah, still active, but i will be off for vacation for several days, and this needs some work so will update in a week. @WillAyd 👍

[simonjayhawkins]

@charlesdong1991 what's the status here?

[charlesdong1991]

emm, let me close for now, haven't past tests locally. will reopen once finding a way.