issue_comments: 340478707

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https://github.com/pydata/xarray/issues/1429#issuecomment-340478707 https://api.github.com/repos/pydata/xarray/issues/1429 340478707 MDEyOklzc3VlQ29tbWVudDM0MDQ3ODcwNw== 1217238 2017-10-30T15:22:46Z 2017-10-30T15:22:46Z MEMBER

I don't think I understand how MemoryCachedArray is being used in xarray. What object would be stored in this array wrapper?

When not using dask and cache=True in open_dataset, we use it to wrap arrays loaded from netCDF files.

Currently, it looks like the object loaded into it is usually a CopyOnWriteArray, which we use to ensure that modifying an xarray object never modifies the file on disk: ``` In [24]: ds2 = xr.open_dataset('foo.nc', engine='netcdf4')

In [25]: ds2.x.variable._data Out[25]: MemoryCachedArray(array=CopyOnWriteArray(array=LazilyIndexedArray(array=<xarray.backends.netCDF4_.NetCDF4ArrayWrapper object at 0x11b3f25c0>, key=OuterIndexer(slice(None, None, None),)))) ```

 
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