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/4205#issuecomment-1176645772,https://api.github.com/repos/pydata/xarray/issues/4205,1176645772,IC_kwDOAMm_X85GIjCM,20629530,2022-07-06T20:00:09Z,2022-07-06T20:00:32Z,CONTRIBUTOR,"I have the same problem in xarray 2022.3.0. 
The issue is that this creates unnecessary dask tasks in the graph and some operations acting on the coordinates unexpectedly trigger dask computations. ""Unexpected"" because the coordinates at the beginning of the process where not chunked. So computation that was expected to happen in the main thread (or not happen at all) is now happenning in the dask workers.

An example:
```python3
import numpy as np
import xarray as xr
from dask.diagnostics import ProgressBar

# A 2D variable
da = xr.DataArray(
    np.ones((12, 10)),
    dims=('x', 'y'),
    coords={'x': np.arange(12), 'y': np.arange(10)}
 )

# A 1D variable sharing a dim with da
db = xr.DataArray(
    np.ones((12,)),
    dims=('x'),
    coords={'x': np.arange(12)}
)

# A non-dimension coordinate
cx = xr.DataArray(np.zeros((12,)), dims=('x',), coords={'x': np.arange(12)})

# Assign it to da and db
da = da.assign_coords(cx=cx)
db = db.assign_coords(cx=cx)

# We need to chunk along y
da = da.chunk({'y': 1})

# Notice how `cx` is now a dask array, even if it is a 1D coordinate and does not have 'Y' as a dimension.
print(da)

# This triggers a dask computation
with ProgressBar():
    da - db
```
The reason my example triggers dask is that xarray ensure the coordinates are aligned and equal (I think?). Anyway, I didn't expect it.

Personally, I think the `chunk` method shouldn't apply to the coordinates at all, no matter their dimensions. They're coordinate so we expect to be able to read them easily when aligning/comparing dataset. Dask is to be used with the ""real"" data only. Does this vision fit the one from the devs?  I feel this ""skip"" could be easily implemented.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,651945063