refactor DaskIndexingAdapter __getitem__ method (#8758)

* remove the unnecessary check for `VectorizedIndexer`

* remvove test

* update whats-new

* update test

* Trim

---------

Co-authored-by: Deepak Cherian <deepak@cherian.net>

doc/whats-new.rst

@@ -102,6 +102,9 @@ Internal Changes
 - Adds :py:func:`open_datatree` into ``xarray/backends`` (:pull:`8697`) By `Matt
   Savoie <https://github.com/flamingbear>`_.
 
+- Refactor  :py:meth:`xarray.core.indexing.DaskIndexingAdapter.__getitem__` to remove an unnecessary rewrite of the indexer key
+  (:issue: `8377`, :pull:`8758`) By `Anderson Banihirwe <https://github.com/andersy005>`
+
 .. _whats-new.2024.01.1:
 
 v2024.01.1 (23 Jan, 2024)

xarray/core/indexing.py

@@ -4,7 +4,7 @@
 import functools
 import operator
 from collections import Counter, defaultdict
-from collections.abc import Hashable, Iterable, Mapping
+from collections.abc import Hashable, Mapping
 from contextlib import suppress
 from dataclasses import dataclass, field
 from datetime import timedelta
@@ -1418,23 +1418,6 @@ def __init__(self, array):
         self.array = array
 
     def __getitem__(self, key):
-        if not isinstance(key, VectorizedIndexer):
-            # if possible, short-circuit when keys are effectively slice(None)
-            # This preserves dask name and passes lazy array equivalence checks
-            # (see duck_array_ops.lazy_array_equiv)
-            rewritten_indexer = False
-            new_indexer = []
-            for idim, k in enumerate(key.tuple):
-                if isinstance(k, Iterable) and (
-                    not is_duck_dask_array(k)
-                    and duck_array_ops.array_equiv(k, np.arange(self.array.shape[idim]))
-                ):
-                    new_indexer.append(slice(None))
-                    rewritten_indexer = True
-                else:
-                    new_indexer.append(k)
-            if rewritten_indexer:
-                key = type(key)(tuple(new_indexer))
 
         if isinstance(key, BasicIndexer):
             return self.array[key.tuple]

xarray/tests/test_dask.py

@@ -1662,16 +1662,10 @@ def test_lazy_array_equiv_merge(compat):
         lambda a: a.assign_attrs(new_attr="anew"),
         lambda a: a.assign_coords(cxy=a.cxy),
         lambda a: a.copy(),
-        lambda a: a.isel(x=np.arange(a.sizes["x"])),
         lambda a: a.isel(x=slice(None)),
         lambda a: a.loc[dict(x=slice(None))],
-        lambda a: a.loc[dict(x=np.arange(a.sizes["x"]))],
-        lambda a: a.loc[dict(x=a.x)],
-        lambda a: a.sel(x=a.x),
-        lambda a: a.sel(x=a.x.values),
         lambda a: a.transpose(...),
         lambda a: a.squeeze(),  # no dimensions to squeeze
-        lambda a: a.sortby("x"),  # "x" is already sorted
         lambda a: a.reindex(x=a.x),
         lambda a: a.reindex_like(a),
         lambda a: a.rename({"cxy": "cnew"}).rename({"cnew": "cxy"}),