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/issues/3535#issuecomment-554317768,https://api.github.com/repos/pydata/xarray/issues/3535,554317768,MDEyOklzc3VlQ29tbWVudDU1NDMxNzc2OA==,10194086,2019-11-15T11:05:44Z,2019-11-15T11:08:29Z,MEMBER,"This happens in `xr.combinde_by_coords`. Note that the `OverflowError` is ""ignored in: `pandas._libs.algos.are_diff'"". So `xr.combinde_by_coords` can return a wrong dataset (although this does not happen silently):

``` python

import xarray as xr
i1 = xr.cftime_range(""4500-12-31"", periods=1)
i2 = xr.cftime_range(""4600-12-31"", periods=1)
i3 = xr.cftime_range(""5100-12-31"", periods=1)

d1 = xr.DataArray([0], dims=(""time"", ), coords={""time"": (""time"", i1)}).to_dataset(name=""a"")
d2 = xr.DataArray([1], dims=(""time"", ), coords={""time"": (""time"", i2)}).to_dataset(name=""a"")
d3 = xr.DataArray([2], dims=(""time"", ), coords={""time"": (""time"", i3)}).to_dataset(name=""a"")

xr.combine_by_coords([d1, d2, d3]).time
```

returns:

``` python
<xarray.DataArray 'time' (time: 2)>
array([cftime.DatetimeGregorian(4500-12-31 00:00:00),
       cftime.DatetimeGregorian(5100-12-31 00:00:00)], dtype=object)
Coordinates:
  * time     (time) object 4500-12-31 00:00:00 5100-12-31 00:00:00
```
note how `d2` is missing.

--------

Within `xr.combine_by_coords` the error happens here:

https://github.com/pydata/xarray/blob/7b4a286f59bc7d60d4e4d03be65562ff63f9b111/xarray/core/combine.py#L98

``` python
import pandas as pd

indexes = [i1, i2, i3]

# the code from _infer_concat_order_from_coords
first_items = pd.Index([index.take([0]) for index in indexes])

series = first_items.to_series()
rank = series.rank(method=""dense"", ascending=ascending)
order = rank.astype(int).values - 1

order
>>> array([0, 1, 1])
```

This causes the second item to be dropped.



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