ENH: Pass on on-disk chunk sizes as preferred chunk sizes to the xarray backend

docs/history.rst

@@ -4,6 +4,7 @@ History
 Latest
 ------
 - BUG: Fix setting spatial dims internally during propagation (pull #682)
+- ENH: Pass on on-disk chunk sizes as preferred chunk sizes to the xarray backend (pull #678)
 
 0.14.1
 ------

rioxarray/_io.py

@@ -1236,7 +1236,7 @@ def open_rasterio(
     )
     result.encoding = encoding
 
-    # update attributes from NetCDF attributess
+    # update attributes from NetCDF attributes
     _load_netcdf_attrs(riods.tags(), result)
     result = _decode_datetime_cf(
         result, decode_times=decode_times, decode_timedelta=decode_timedelta
@@ -1262,6 +1262,12 @@ def open_rasterio(
 
     if chunks is not None:
         result = _prepare_dask(result, riods, filename, chunks)
+    else:
+        result.encoding["preferred_chunks"] = {
+            result.rio.y_dim: riods.block_shapes[0][0],
+            result.rio.x_dim: riods.block_shapes[0][1],
+            coord_name: 1,
+        }
 
     # add file path to encoding
     result.encoding["source"] = riods.name

rioxarray/xarray_plugin.py

@@ -38,8 +38,6 @@ def open_dataset(
         filename_or_obj,
         drop_variables=None,
         parse_coordinates=None,
-        chunks=None,
-        cache=None,
         lock=None,
         masked=False,
         mask_and_scale=True,
@@ -56,8 +54,7 @@ def open_dataset(
         rds = _io.open_rasterio(
             filename_or_obj,
             parse_coordinates=parse_coordinates,
-            chunks=chunks,
-            cache=cache,
+            cache=False,
             lock=lock,
             masked=masked,
             mask_and_scale=mask_and_scale,

test/integration/test_integration__io.py

@@ -1121,6 +1121,7 @@ def test_mask_and_scale(open_rasterio):
             "grid_mapping": "crs",
             "dtype": "uint16",
             "rasterio_dtype": "uint16",
+            "preferred_chunks": dict(band=1, x=1386, y=585),
         }
         attrs = rds.air_temperature.attrs
         assert "_Unsigned" not in attrs
@@ -1146,6 +1147,7 @@ def test_no_mask_and_scale(open_rasterio):
             "grid_mapping": "crs",
             "dtype": "uint16",
             "rasterio_dtype": "uint16",
+            "preferred_chunks": {"band": 1, "x": 1386, "y": 585},
         }
         attrs = rds.air_temperature.attrs
         assert attrs["_Unsigned"] == "true"

test/integration/test_integration_xarray_plugin.py

@@ -20,6 +20,7 @@ def test_xarray_open_dataset():
     assert "spatial_ref" in ds.coords
     assert "grid_mapping" not in ds.data_vars["band_data"].attrs
     assert "grid_mapping" in ds.data_vars["band_data"].encoding
+    assert "preferred_chunks" in ds.data_vars["band_data"].encoding
 
     ds = xarray.open_dataset(cog_file)