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/pull/5284#issuecomment-837097308,https://api.github.com/repos/pydata/xarray/issues/5284,837097308,MDEyOklzc3VlQ29tbWVudDgzNzA5NzMwOA==,2448579,2021-05-10T18:25:29Z,2021-05-10T18:25:29Z,MEMBER,"Well that was confusing! `if missing_vals.any():` will not be triggered if all the values in a block are valid. With `.chunk({""time"": 1})`, some of the blocks are all valid.

I discovered this with `print` debugging and the single-threaded scheduler which loops over blocks in a for-loop
```
# Define function to use in map_blocks
def _get_valid_values(da, other):
    da1, da2 = xr.align(da, other, join=""inner"", copy=False)
    
    # 2. Ignore the nans
    missing_vals = np.logical_or(da1.isnull(), da2.isnull())
    print(missing_vals)
    
    if missing_vals.any():
        da = da.where(missing_vals)
    return da

da_a.map_blocks(_get_valid_values, args=[da_b]).compute(scheduler=""sync"")
```

For better performance, we should try a `dask.array.map_blocks` approach with `duck_array_ops.isnull` ","{""total_count"": 1, ""+1"": 1, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,882876804