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Fix decode cf with dask #2047

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Apr 12, 2018
Merged

Fix decode cf with dask #2047

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b9276ad
fixes #1372
rabernat Apr 10, 2018
c884300
what's new
rabernat Apr 10, 2018
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2 changes: 2 additions & 0 deletions doc/whats-new.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,8 @@ Enhancements
Bug fixes
~~~~~~~~~

- Fixed ``decode_cf`` function to operate lazily on dask arrays
(:issue:`1372`). By `Ryan Abernathey <https://github.com/rabernat>`_.
- Fixed labeled indexing with slice bounds given by xarray objects with
datetime64 or timedelta64 dtypes (:issue:`1240`).
By `Stephan Hoyer <https://github.com/shoyer>`_.
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7 changes: 4 additions & 3 deletions xarray/conventions.py
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Expand Up @@ -9,7 +9,7 @@
from .coding import times, variables
from .coding.variables import SerializationWarning
from .core import duck_array_ops, indexing
from .core.pycompat import OrderedDict, basestring, iteritems
from .core.pycompat import OrderedDict, basestring, iteritems, dask_array_type
from .core.variable import IndexVariable, Variable, as_variable


Expand Down Expand Up @@ -490,8 +490,9 @@ def decode_cf_variable(name, var, concat_characters=True, mask_and_scale=True,
del attributes['dtype']
data = BoolTypeArray(data)

return Variable(dimensions, indexing.LazilyOuterIndexedArray(data),
attributes, encoding=encoding)
if not isinstance(data, dask_array_type):
data = indexing.LazilyOuterIndexedArray(data)
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This is the offending line which caused the dask arrays to stop being dask arrays. I have simply bypassed it for dask arrays. This didn't break any tests. But can we think of any unforeseen negative consequences? What does LazilyOuterIndexedArray do here? I have to admit that I don't understand the details of our new indexing wrappers.

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LazilyOuterIndexedArray makes indexing on non-dask arrays lazy. It's not necessary or useful for dask arrays.

return Variable(dimensions, data, attributes, encoding=encoding)


def decode_cf_variables(variables, attributes, concat_characters=True,
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13 changes: 12 additions & 1 deletion xarray/tests/test_conventions.py
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Expand Up @@ -18,7 +18,7 @@

from . import (
IndexerMaker, TestCase, assert_array_equal, raises_regex, requires_netCDF4,
requires_netcdftime, unittest)
requires_netcdftime, unittest, requires_dask)
from .test_backends import CFEncodedDataTest

B = IndexerMaker(indexing.BasicIndexer)
Expand Down Expand Up @@ -332,6 +332,17 @@ def test_decode_cf_datetime_transition_to_invalid(self):

assert_array_equal(ds_decoded.time.values, expected)

@requires_dask
def test_decode_cf_with_dask(self):
import dask
original = Dataset({
't': ('t', [0, 1, 2], {'units': 'days since 2000-01-01'}),
'foo': ('t', [0, 0, 0], {'coordinates': 'y', 'units': 'bar'}),
'y': ('t', [5, 10, -999], {'_FillValue': -999})
}).chunk({'t': 1})
decoded = conventions.decode_cf(original)
assert dask.is_dask_collection(decoded.y.data)
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Is this an appropriate place to test for this? There is no other dask stuff in test_conventions.py, but it seemed to make sense there.

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This looks like a fine place to me.



class CFEncodedInMemoryStore(WritableCFDataStore, InMemoryDataStore):
pass
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