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Could we defer to flox for GroupBy.first? #9647

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#10148
#9986
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Could we defer to flox for GroupBy.first?#9647
#10148
#9986
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enhancementtopic-groupby
@max-sixty

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@max-sixty
max-sixty
opened on Oct 18, 2024

Is your feature request related to a problem?

I was wondering why a groupby("foo").first() call was going so slowly — I think we run a python loop for this, rather than calling into flox:

xarray/xarray/core/groupby.py

Lines 1218 to 1231 in b9780e7

def _first_or_last(self, op, skipna, keep_attrs):
if all(
isinstance(maybe_slice, slice)
and (maybe_slice.stop == maybe_slice.start + 1)
for maybe_slice in self.encoded.group_indices
):
# NB. this is currently only used for reductions along an existing
# dimension
return self._obj
if keep_attrs is None:
keep_attrs = _get_keep_attrs(default=True)
return self.reduce(
op, dim=[self._group_dim], skipna=skipna, keep_attrs=keep_attrs
)

Describe the solution you'd like

Could we call into flox? Numbagg has the routines...

Describe alternatives you've considered

No response

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No response

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