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/1077#issuecomment-1268380486,https://api.github.com/repos/pydata/xarray/issues/1077,1268380486,IC_kwDOAMm_X85LmfNG,5230109,2022-10-05T12:38:05Z,2022-10-05T12:38:05Z,NONE,"Hi everyone, first of all, thanks for your amazing work! I came across this issue today because I have a dataset with multiple variables and multiple multi index dimensions, some of which aren't used in some variable. I had to slightly adapt the workaround posted by @dcherian to get things to work. I'll post it here if someone else finds the patch useful. I'm not sure if it would be a viable fix for the issue though, let me know if it is and I'll open a PR.

```python
def encode_multiindex(ds, idxname):
    encoded = ds.reset_index(idxname)
    coords = dict(zip(ds.indexes[idxname].names, ds.indexes[idxname].levels))
    for coord in coords:
        encoded[coord] = coords[coord].values
    shape = [encoded.sizes[coord] for coord in coords]
    encoded[idxname] = np.ravel_multi_index(ds.indexes[idxname].codes, shape)
    encoded[idxname].attrs[""compress""] = "" "".join(ds.indexes[idxname].names)
    return encoded


def decode_to_multiindex(encoded, idxname):
    names = encoded[idxname].attrs[""compress""].split("" "")
    shape = [encoded.sizes[dim] for dim in names]
    indices = np.unravel_index(encoded[idxname].values, shape)
    arrays = np.array([encoded[dim].values[index] for dim, index in zip(names, indices)])
    mindex = pd.MultiIndex.from_arrays(arrays, names=names)

    decoded = xr.Dataset(
        {},
        dict(
            **{idxname: mindex},
            **{dim: encoded.coords[dim] for dim in encoded.dims if dim not in [idxname] + names}
        )
    )
    for varname in encoded.data_vars:
        if idxname in encoded[varname].dims:
            decoded[varname] = (encoded[varname].dims, encoded[varname].values)
        else:
            decoded[varname] = encoded[varname]
    return decoded
```","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,187069161