html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/pull/4746#issuecomment-766462310,https://api.github.com/repos/pydata/xarray/issues/4746,766462310,MDEyOklzc3VlQ29tbWVudDc2NjQ2MjMxMA==,5635139,2021-01-24T23:48:00Z,2021-01-24T23:48:00Z,MEMBER,Let me know any post-merge feedback and I'll make the changes,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-763903671,https://api.github.com/repos/pydata/xarray/issues/4746,763903671,MDEyOklzc3VlQ29tbWVudDc2MzkwMzY3MQ==,5635139,2021-01-20T20:12:36Z,2021-01-20T20:12:36Z,MEMBER,Any final feedback before merging?,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-760532922,https://api.github.com/repos/pydata/xarray/issues/4746,760532922,MDEyOklzc3VlQ29tbWVudDc2MDUzMjkyMg==,5635139,2021-01-14T23:07:16Z,2021-01-14T23:07:16Z,MEMBER,Would anyone know whether the docs failure is related to this PR? I can't see anything in the log apart from matplotlib warnings? https://readthedocs.org/projects/xray/builds/12768566/,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-760532153,https://api.github.com/repos/pydata/xarray/issues/4746,760532153,MDEyOklzc3VlQ29tbWVudDc2MDUzMjE1Mw==,5635139,2021-01-14T23:05:16Z,2021-01-14T23:05:16Z,MEMBER,"I double-checked the benchmarks and added a pandas comparison. That involved ensuring the missing value was handled corre them and ensured the setup wasn't in the benchmark.

I don't get the 100x speed-up that I thought I saw initially; it's now more like 8x. Still decent! I'm not sure whether that's because I misread the benchmark previously or because the benchmarks are slightly different — I guess the first.

Pasting below the results so we have something concrete.

Existing
```
asv profile unstacking.Unstacking.time_unstack_slow master | head -n 20
··· unstacking.Unstacking.time_unstack_slow                   861±20ms
```

Proposed
```
asv profile unstacking.Unstacking.time_unstack_slow HEAD | head -n 20
··· unstacking.Unstacking.time_unstack_slow                    108±3ms
```

Pandas
```
asv profile unstacking.Unstacking.time_unstack_pandas_slow master | head -n 20
··· unstacking.Unstacking.time_unstack_pandas_slow            207±10ms
```

Are we OK with the claim vs pandas? I think it's important that we make accurate comparisons (both good and bad) but open-minded if it seems a bit aggressive. Worth someone reviewing the code in the benchmark to ensure I haven't made a mistake.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-758143460,https://api.github.com/repos/pydata/xarray/issues/4746,758143460,MDEyOklzc3VlQ29tbWVudDc1ODE0MzQ2MA==,5635139,2021-01-11T18:37:48Z,2021-01-11T18:37:48Z,MEMBER,Any final comments before merging?,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-755420263,https://api.github.com/repos/pydata/xarray/issues/4746,755420263,MDEyOklzc3VlQ29tbWVudDc1NTQyMDI2Mw==,5635139,2021-01-06T16:48:30Z,2021-01-06T16:48:30Z,MEMBER,"As discussed in dev meeting, https://github.com/dask/dask/pull/7033 would allow dask to use the fast path, and likely eventually for our existing path to be removed","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-754401859,https://api.github.com/repos/pydata/xarray/issues/4746,754401859,MDEyOklzc3VlQ29tbWVudDc1NDQwMTg1OQ==,5635139,2021-01-05T05:14:27Z,2021-01-05T05:14:27Z,MEMBER,"Tests now pass after merging master, not sure whether the previous tests were flaky vs something upstream changed...

Ready for a final review","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-753778517,https://api.github.com/repos/pydata/xarray/issues/4746,753778517,MDEyOklzc3VlQ29tbWVudDc1Mzc3ODUxNw==,5635139,2021-01-04T06:11:17Z,2021-01-04T06:11:17Z,MEMBER,"This still seems to be getting a bunch of pint failures, like this one: https://dev.azure.com/xarray/xarray/_build/results?buildId=4657&view=ms.vss-test-web.build-test-results-tab&runId=73796&resultId=110407&paneView=debug

I confused, since this PR now has no mention of `pint` and I don't see any mention of unstacking in those test failures. I suspect I'm missing something. Any ideas for what could be happening?","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-753683611,https://api.github.com/repos/pydata/xarray/issues/4746,753683611,MDEyOklzc3VlQ29tbWVudDc1MzY4MzYxMQ==,5635139,2021-01-03T22:14:17Z,2021-01-03T22:14:17Z,MEMBER,"Until https://github.com/pydata/xarray/pull/4751 is resolved, I've taken out the explicit pint check and replaced with a numpy check.

The code is a bit messy now — now two levels of comments. But I've put references in, so it should be tractable. Lmk any feedback.

Otherwise this is ready to go from my end.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-753430518,https://api.github.com/repos/pydata/xarray/issues/4746,753430518,MDEyOklzc3VlQ29tbWVudDc1MzQzMDUxOA==,5635139,2021-01-02T04:37:26Z,2021-01-02T04:37:26Z,MEMBER,"I'm not sure whether I'm making some very basic mistake, but I'm seeing what seems like a very surprising error.

After the most recent commit, which seems to do very little apart from import `pint` iff it's available: https://github.com/pydata/xarray/pull/4746/commits/b33adedbfbd92df0f4188568691c7e2915bf8c19, I'm getting a lot of pint errors, unrelated to `unstack` / `stack`.

Here's the results from the run prior:
https://dev.azure.com/xarray/xarray/_build/results?buildId=4650&view=ms.vss-test-web.build-test-results-tab

And from this run:
https://dev.azure.com/xarray/xarray/_build/results?buildId=4651&view=ms.vss-test-web.build-test-results-tab

Any ideas what's happening? As ever, 30% chance that I made a obvious typo that I can't see... Thanks in advance.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-753427050,https://api.github.com/repos/pydata/xarray/issues/4746,753427050,MDEyOklzc3VlQ29tbWVudDc1MzQyNzA1MA==,5635139,2021-01-02T03:56:19Z,2021-01-02T03:56:19Z,MEMBER,Thank you @jthielen !,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-753425993,https://api.github.com/repos/pydata/xarray/issues/4746,753425993,MDEyOklzc3VlQ29tbWVudDc1MzQyNTk5Mw==,5635139,2021-01-02T03:43:06Z,2021-01-02T03:43:06Z,MEMBER,"I imagine I'm making some basic error here, but what's the best approach for evaluating whether an array is a pint array?

`isinstance(self.data, unit_registry.Quantity)` returns False, though seems to be what we do in `test_units.py`?

```
(Pdb) unit_registry
<pint.registry.UnitRegistry object at 0x13d4574c0>
(Pdb) unit_registry.Quantity
<class 'pint.quantity.build_quantity_class.<locals>.Quantity'>
(Pdb) isinstance(self.data, unit_registry.Quantity)
False
(Pdb) self.data
<Quantity([ 0.          0.20408163  0.40816327  0.6122449   0.81632653  1.02040816
  1.2244898   1.42857143  1.63265306  1.83673469  2.04081633  2.24489796
  2.44897959  2.65306122  2.85714286  3.06122449  3.26530612  3.46938776
  3.67346939  3.87755102  4.08163265  4.28571429  4.48979592  4.69387755
  4.89795918  5.10204082  5.30612245  5.51020408  5.71428571  5.91836735
  6.12244898  6.32653061  6.53061224  6.73469388  6.93877551  7.14285714
  7.34693878  7.55102041  7.75510204  7.95918367  8.16326531  8.36734694
  8.57142857  8.7755102   8.97959184  9.18367347  9.3877551   9.59183673
  9.79591837 10.        ], 'meter')>
(Pdb) self.data.__class__
<class 'pint.quantity.build_quantity_class.<locals>.Quantity'>
```","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-753425173,https://api.github.com/repos/pydata/xarray/issues/4746,753425173,MDEyOklzc3VlQ29tbWVudDc1MzQyNTE3Mw==,5635139,2021-01-02T03:30:35Z,2021-01-02T03:30:35Z,MEMBER,"Thanks for responding @jthielen .

Yes, so `full_like` isn't creating a pint array:

```
(Pdb) self.data
<Quantity([ 0.          0.20408163  0.40816327  0.6122449   0.81632653  1.02040816
  1.2244898   1.42857143  1.63265306  1.83673469  2.04081633  2.24489796
  2.44897959  2.65306122  2.85714286  3.06122449  3.26530612  3.46938776
  3.67346939  3.87755102  4.08163265  4.28571429  4.48979592  4.69387755
  4.89795918  5.10204082  5.30612245  5.51020408  5.71428571  5.91836735
  6.12244898  6.32653061  6.53061224  6.73469388  6.93877551  7.14285714
  7.34693878  7.55102041  7.75510204  7.95918367  8.16326531  8.36734694
  8.57142857  8.7755102   8.97959184  9.18367347  9.3877551   9.59183673
  9.79591837 10.        ], 'meter')>
(Pdb) np.full_like(self.data, fill_value=fill_value)
array([nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
       nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
       nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
       nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan])
(Pdb) fill_value
nan
```

I do think this is a bit surprising — while `fill_value` isn't typed, it's compatible with the existing type.

For the moment, I'll direct pint arrays to take the existing code path — I'm more confident that we don't want to special-case pint in the `unstack` routine.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-753406775,https://api.github.com/repos/pydata/xarray/issues/4746,753406775,MDEyOklzc3VlQ29tbWVudDc1MzQwNjc3NQ==,5635139,2021-01-02T00:03:00Z,2021-01-02T00:03:00Z,MEMBER,"Would anyone be able be familiar with this pint error? https://dev.azure.com/xarray/xarray/_build/results?buildId=4650&view=ms.vss-test-web.build-test-results-tab&runId=73654&resultId=111454&paneView=debug

It seems to be failing on the assignment: `data[(..., *indexer)] = reordered`, rather than anything specific to unstacking.

Here's the stack trace from there:

```python
/home/vsts/work/1/s/xarray/core/variable.py:1627: in _unstack_once
    data[(..., *indexer)] = reordered
/home/vsts/work/1/s/xarray/core/common.py:131: in __array__
    return np.asarray(self.values, dtype=dtype)
/home/vsts/work/1/s/xarray/core/variable.py:543: in values
    return _as_array_or_item(self._data)
/home/vsts/work/1/s/xarray/core/variable.py:275: in _as_array_or_item
    data = np.asarray(data)
/usr/share/miniconda/envs/xarray-tests/lib/python3.8/site-packages/numpy/core/_asarray.py:83: in asarray
    return array(a, dtype, copy=False, order=order)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <Quantity([ 0  0  0  0  0  1  1  1  1  1  2  2  2  2  2  3  3  3  3  3  4  4  4  4
  4  5  5  5  5  5  6  6  6  6  6  7  7  7  7  7  8  8  8  8  8  9  9  9
  9 10], 'meter')>
t = None

    def __array__(self, t=None):
>       warnings.warn(
            ""The unit of the quantity is stripped when downcasting to ndarray."",
            UnitStrippedWarning,
            stacklevel=2,
        )
E       pint.errors.UnitStrippedWarning: The unit of the quantity is stripped when downcasting to ndarray.

/usr/share/miniconda/envs/xarray-tests/lib/python3.8/site-packages/pint/quantity.py:1683: UnitStrippedWarning
```

Worst case, I can direct pint arrays to the existing unstack path, but ideally this would work.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-753391636,https://api.github.com/repos/pydata/xarray/issues/4746,753391636,MDEyOklzc3VlQ29tbWVudDc1MzM5MTYzNg==,5635139,2021-01-01T22:03:19Z,2021-01-01T22:03:19Z,MEMBER,"Great, thanks, I'm making that change.

Is there any need to keep the `sparse` kwarg? My inclination is to remove it and retain types — so to get a sparse array back, convert to sparse before unstacking?","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550
https://github.com/pydata/xarray/pull/4746#issuecomment-753225789,https://api.github.com/repos/pydata/xarray/issues/4746,753225789,MDEyOklzc3VlQ29tbWVudDc1MzIyNTc4OQ==,5635139,2020-12-31T23:38:33Z,2020-12-31T23:38:33Z,MEMBER,"Any ideas on how sparse arrays should be handled in `unstack`? Currently we use reindex, so this seems to pass through without much effort on our part. 

In the new code, we're creating an array with `np.full` and then assigning to the appropriate locations. Can we do something similar that's not dependent on the underlying numpy / sparse / dask storage?","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,777153550