BUG: Try to sort result of Index.union rather than guessing sortability #17378

toobaz · 2017-08-30T06:30:30Z

closes Union of indexes of tuples is not sorted #17376
tests added / passed
passes git diff master -u -- "*.py" | flake8 --diff
whatsnew entry

The lines of code I removed seemed written with the intention of guaranteeing the same result under Python 2 and 3, but the docs say "Form the union of two Index objects and sorts if possible.": so if it is possible in Python 2 we should do it, regardless of whether it is in Python 3. After all, this is how .sort_values() works. And more practically, trying to guess whether the result of an union can be sorted is hard.

codecov · 2017-08-30T07:52:01Z

Codecov Report

Merging #17378 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@ Coverage Diff @@ ## master #17378 +/- ## ========================================== - Coverage 91.01% 90.99% -0.02%  ========================================== Files 163 163 Lines 49567 49559 -8 ========================================== - Hits 45113 45096 -17  - Misses 4454 4463 +9

Flag	Coverage Δ
#multiple	`88.77% <100%> (-0.01%)`	⬇️
#single	`40.25% <60%> (-0.07%)`	⬇️

Impacted Files	Coverage Δ
pandas/core/indexes/base.py	`95.86% <100%> (-0.02%)`	⬇️
pandas/io/gbq.py	`25% <0%> (-58.34%)`	⬇️
pandas/core/frame.py	`97.72% <0%> (-0.1%)`	⬇️

Continue to review full report at Codecov.

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codecov · 2017-08-30T07:52:13Z

Codecov Report

Merging #17378 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@ Coverage Diff @@ ## master #17378 +/- ## ========================================== - Coverage 91.72% 91.72% -0.01%  ========================================== Files 150 150 Lines 49122 49104 -18 ========================================== - Hits 45057 45039 -18  Misses 4065 4065

Flag	Coverage Δ
#multiple	`90.1% <100%> (-0.01%)`	⬇️
#single	`41.86% <60%> (ø)`	⬆️

Impacted Files	Coverage Δ
pandas/core/indexes/base.py	`96.65% <100%> (-0.02%)`	⬇️
pandas/core/reshape/tile.py	`92.94% <0%> (-0.43%)`	⬇️
pandas/core/window.py	`96.31% <0%> (ø)`	⬆️

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jreback · 2017-08-30T10:11:26Z

pandas/core/indexes/base.py

-  warnings.warn("%s, sort order is undefined for "
-  "incomparable objects" % e, RuntimeWarning,
-  stacklevel=3)
+ try:


you probably can simply use core.sorting.safe_sort here instead and just remove the warning entirely (as it fails in many less cases)

Done, but I left the warning as it's still raised if not even safe_sort can sort them.

(I assume the failure is a problem with AppVeyor)

toobaz · 2017-09-06T17:05:28Z

Any idea about what's happening with AppVeyor? It fails reliably on this PR with 2.7, but the trace doesn't point at any specific test.

gfyoung · 2017-09-06T17:23:44Z

@toobaz : Nope, not a clue 😢 . There's no way your changes AFAICT could have caused internal errors on the build. I restarted AppVeyor to double check.

toobaz · 2017-09-06T22:11:20Z

I restarted AppVeyor to double check.

Failed again... shall I try closing this and opening a new PR?

jreback · 2017-09-07T00:33:10Z

Failed again... shall I try closing this and opening a new PR?

NO. that just creates more work. let me look.

jreback · 2017-09-07T00:36:44Z

ok this is a legitimate catch. pytest-dist is segfaulting, hiding the traceback. So a couple of options to debug.

setup a vm on 3.6/windows is easiest / best.

you can temporarily change the options in the test runner (in ci/scripts_multiple.py) to something like:
pytest -v -r xX -m "not single" --junitxml=/tmp/multiple.xml $TEST_ARGS pandas

which disables the multi-processing and shows each test (so you can see where its failing).

jreback · 2017-09-07T00:37:33Z

it looks like its either segfaulting or in a recursive loop somewhere.

toobaz · 2017-09-07T05:17:20Z

setup a vm on 3.6/windows is easiest / best.

Do you mean Python 3.6?! (tests fail only on 2.7)

gfyoung · 2017-09-07T05:18:26Z

@toobaz : I think @jreback probably meant 2.7 😄

jreback · 2017-10-14T19:24:58Z

@toobaz this is related to #17839, could simply recast this to add the sort= kwarg (I think for back compat we have to use =False, but maybe be able to change that, not sure).

toobaz · 2017-10-15T07:12:50Z

@toobaz this is related to #17839, could simply recast this to add the sort= kwarg (I think for back compat we have to use =False, but maybe be able to change that, not sure).

Certainly related, but I'm confused: are you suggesting the two methods should share more code? Or just that Index.union too should have a sort= argument? In this case I think that for backward compatibility it should default to True...

jreback · 2017-10-31T01:22:55Z

Certainly related, but I'm confused: are you suggesting the two methods should share more code? Or just that Index.union too should have a sort= argument? In this case I think that for backward compatibility it should default to True...

yes I would add a sort=True kwarg.

jreback · 2017-11-25T16:20:48Z

can you rebase. I think we do want to add this kw.

toobaz · 2017-11-26T00:33:01Z

Unfortunately the problem on Windows + Python 2.7 persists. I haven't found the time to set up a virtual machine to debug.

jreback · 2018-01-21T18:17:28Z

@toobaz if you can rebase would be great. I would also be ok with simply adding the keyword w/o changing much code as a first step.

gfyoung · 2018-03-03T22:19:31Z

Hmmm...so this issue might be known with pytest (or its plugins) already:

pytest-dev/pytest#2223

Still not sure how @toobaz is triggering that though.

Unless anyone has any other insights into this, I feel inclined to file an issue against one of the pytest repositories and see what they have to say.

toobaz · 2018-03-04T09:35:36Z

Maybe we could ask whether there is a way to use this catchsegv within a pytest run?

gfyoung · 2018-03-06T23:04:49Z

Maybe we could ask whether there is a way to use this catchsegv within a pytest run?

@toobaz : Well, this is a Windows machine, not UNIX 😢

I notice that we are using pytest-forked, which AFAICT, isn't well-supported on Windows:

https://github.com/pytest-dev/pytest-forked

I was about to file an issue against pytest-xdist, but I wonder if this might be the problem child.

toobaz · 2018-03-06T23:20:48Z

@toobaz : Well, this is a Windows machine, not UNIX cry

right 🙄

I was about to file an issue against pytest-xdist, but I wonder if this might be the problem child.

What makes you think this is a bug in pytest, not a segfault somewhere in pandas? (or do you think it's both?)

gfyoung · 2018-03-07T02:27:51Z

What makes you think this is a bug in pytest, not a segfault somewhere in pandas? (or do you think it's both?)

I'm highly skeptical that your changes are causing a segfault. That would be pretty impressive actually given that you're only touching high-level Python 😄

In addition, I've tested your changes on multiple OS's (Windows including). No segfault anywhere.

gfyoung · 2018-03-07T05:05:18Z

So removing xdist + rebasing somehow resulted in test failures on the first machine?

Going to leave this PR alone for now until master is patched,

toobaz · 2018-03-07T08:27:11Z

I'm highly skeptical that your changes are causing a segfault. That would be pretty impressive actually given that you're only touching high-level Python

Sure, that would require that my changes are triggering a bug somewhere in lower-level code... but I consider this more probable than a bug in pydist which affects precisely that test, in precisely this PR.

Then again, I'm definitely not an expert.

gfyoung · 2018-03-07T09:05:40Z

I suppose, but if it's a bug in your code, I haven't been able to reproduce it locally.

toobaz · 2018-03-07T09:21:46Z

I suppose, but if it's a bug in your code, I haven't been able to reproduce it locally.

Aha! I had missed that you were testing on Windows. Good to know.

closes pandas-dev#17376

This will probably slow down performance, but I can't see where the bug is in the changes.

jreback · 2018-03-10T01:14:23Z

appveyor.yml


 # create our env
- - cmd: conda create -n pandas python=%PYTHON_VERSION% cython pytest>=3.1.0 pytest-xdist
+ - cmd: conda create -n pandas python=%PYTHON_VERSION% cython pytest>=3.1.0


so does xdist cause the issues with this?

It's really hard to tell at the moment. I've just been experimenting. I'm just at a loss right now as to how that one build on AppVeyor is crashing is so badly with changes like these.

gfyoung · 2018-03-10T18:18:28Z

@toobaz @jreback : So good news (I guess?), I was able to replicate the AppVeyor failure locally.

gfyoung · 2018-03-10T21:36:00Z

@toobaz : It appears that you loosened the sorting restrictions too much, at least for Windows:

The test that is breaking AppVeyor is TestAlignment.test_basic_frame_alignment
The condition where len(indexer) > 0 is the problem. For some reason, I need to put back the comparison of lvals[0] and other_diff[0] to remove the break OR only trying sorting when in the else branch (i.e. when len(indexer) = 0).

toobaz · 2018-03-11T18:45:41Z

@gfyoung thanks for your analysis!

Does the problem arise with any specific combination of index types? (from args = product(...)

gfyoung · 2018-03-11T20:48:03Z

Does the problem arise with any specific combination of index types?

I can't tell unfortunately. It seems to have crashed with multiple types.

jreback · 2018-04-14T13:38:44Z

@toobaz whats' the status on this?

jreback · 2018-10-11T01:49:29Z

closing as stale, if you want to continue working, pls ping and we can re-open. you will need to merge master.

toobaz force-pushed the index_union_sort branch 2 times, most recently from 1ca8f9c to 35c2ec7 Compare August 30, 2017 07:51

jreback requested changes Aug 30, 2017

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jreback added 2/3 Compat Bug Reshaping Concat, Merge/Join, Stack/Unstack, Explode labels Aug 30, 2017

toobaz force-pushed the index_union_sort branch 2 times, most recently from 0a0e0f2 to 0a725fc Compare August 30, 2017 14:07

toobaz force-pushed the index_union_sort branch 3 times, most recently from bc4b8ba to e533022 Compare September 6, 2017 15:23

jreback mentioned this pull request Oct 14, 2017

ENH: sort=bool keyword argument for index.difference #17839

Closed

toobaz force-pushed the index_union_sort branch from e533022 to 83398d9 Compare October 29, 2017 10:32

toobaz force-pushed the index_union_sort branch from 83398d9 to decaa47 Compare November 25, 2017 17:15

gfyoung force-pushed the index_union_sort branch 3 times, most recently from 156fd86 to f4571a2 Compare March 7, 2018 04:00

gfyoung force-pushed the index_union_sort branch from f4571a2 to 953ccc6 Compare March 9, 2018 02:14

toobaz and others added 3 commits March 9, 2018 20:01

BUG: Try to sort result of Index.union rather than guessing sortability

9fceb51

closes pandas-dev#17376

CLN: Fix flake8 errors

7e70fd7

[DO NOT MERGE] Is it pytest-xdist?

899c040

This will probably slow down performance, but I can't see where the bug is in the changes.

gfyoung force-pushed the index_union_sort branch from 953ccc6 to 899c040 Compare March 10, 2018 01:03

jreback reviewed Mar 10, 2018

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toobaz added a commit to toobaz/pandas that referenced this pull request Apr 24, 2018

BUG: workaround failure of pandas-dev#17378 on Windows

8d2e40d

toobaz mentioned this pull request Apr 24, 2018

Index union sort hack #20809

Closed

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toobaz added a commit to toobaz/pandas that referenced this pull request Apr 24, 2018

BUG: workaround failure of pandas-dev#17378 on Windows

c07e91e

jreback mentioned this pull request Sep 25, 2018

BUG: Maintain column order with groupby.nth #22811

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jreback closed this Oct 11, 2018

reidy-p mentioned this pull request Dec 31, 2018

ENH: Add sort parameter to other set operations if possible #24471

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BUG: Try to sort result of Index.union rather than guessing sortability #17378

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