issue_comments: 626207771

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https://github.com/pydata/xarray/pull/4035#issuecomment-626207771 https://api.github.com/repos/pydata/xarray/issues/4035 626207771 MDEyOklzc3VlQ29tbWVudDYyNjIwNzc3MQ== 1217238 2020-05-09T17:14:46Z 2020-05-09T17:14:46Z MEMBER

I'm curious how this interacts with dimension coordinates. Your example bypasses this. But what if dimension coordinates are present. How do we handle alignment issues? For example, what if I call ds.to_zarr(path , region=selection), but the dimension coordinates of ds don't align with the dimension coordinates of the store at path"

It’s entirely unsafe. Currently the coordinates would be overridden with the new values , which is consistent with how to_netcdf() with mode=‘a’ works.

This is probably another good reason for requiring users to explicitly drop variables that don’t include a dimension in the selected region, because at least in that case there can be no user expectations about alignment with coordinates that don’t exist.

In the long term, it might make sense to make both to_netcdf and to_zarr check coordinates by alignment by default, but we wouldn’t want that in all cases, because sometimes users really do want to update variables.

 
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