issue_comments: 868735859

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https://github.com/pydata/xarray/issues/5529#issuecomment-868735859 https://api.github.com/repos/pydata/xarray/issues/5529 868735859 MDEyOklzc3VlQ29tbWVudDg2ODczNTg1OQ== 14371165 2021-06-25T17:54:00Z 2021-06-25T17:54:00Z MEMBER

I think it's some lazy calculation that kicks in. Because I can reproduce using np.asarray.

```python import numpy as np import xarray as xr

ds = xr.tutorial.load_dataset("air_temperature") da = ds["air"].stack(z=[...])

coord = da.z.variable.to_index_variable()

This is very slow:

a = np.asarray(coord)

da.repr_html() ``` 

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