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Compute method if_else seems to create an invalid Dictionary Array #47886
Description
Describe the bug, including details regarding any error messages, version, and platform.
When if_else() is performed on two ChunkedArrays of ordered dictionary type, the resultant ChunkedArray is somewhat strange:
import pyarrow as pa
import pyarrow.compute as pc
dictionary = ["a", "b", "c"]
c1 = pa.DictionaryArray.from_arrays(pa.array([0,1,0], type=pa.int32()), dictionary, ordered=True)
c2 = pa.DictionaryArray.from_arrays(pa.array([2,1,0], type=pa.int32()), dictionary, ordered=True)
c3 = pa.DictionaryArray.from_arrays(pa.array([1,1,0], type=pa.int32()), dictionary, ordered=True)
left = pa.chunked_array([c1, c2, c3])
print(left.type) # ordered=True
c1 = pa.DictionaryArray.from_arrays(pa.array([0,1,0], type=pa.int32()), dictionary, ordered=True)
c2 = pa.DictionaryArray.from_arrays(pa.array([2,None,0], type=pa.int32()), dictionary, ordered=True)
c3 = pa.DictionaryArray.from_arrays(pa.array([None,1,0], type=pa.int32()), dictionary, ordered=True)
right = pa.chunked_array([c1, c2, c3])
print(right.type) # ordered=True
mask = pc.is_null(right)
res = pc.if_else(mask, left, right)
print(res.type) # ordered=True
print(res.chunk(0).type) # ordered=False
print(res.chunk(1).type) # ordered=False
print(res.chunk(2).type) # ordered=Falseres.type shows ordered=True, while the internal chunks are unordered.
If internal chunks are unordered, should not the ChunkedArray (res) be marked as unordered as well?
It causes some internal issues in my application (I am using C++ interface: arrow::compute::CallFunction) aborting my program with: Array chunks must all be same type.
PS. I checked with nightly package and it seems to be there as well:
pip install -i https://pypi.anaconda.org/scientific-python-nightly-wheels/simple pyarrow
Looking forward to your input/suggestion on this.
Thanks and Regards,
Sourav Saha
Component(s)
C++, Python
Activity
goldigd05 commentedon Jan 4, 2026
Hi, I would like to report a bug in
if_elsewhen used on ordered dictionary ChunkedArrays.Currently, the resulting ChunkedArray reports
ordered=Trueat the top level,but its internal chunks are
ordered=False. This can cause C++ errors like"Array chunks must all be same type" when using
arrow::compute::CallFunction.I suggest that
if_elseshould either:orderedproperty for each internal chunk, orI can help reproduce this in a minimal test and propose a fix.
thisisnic commentedon Oct 20, 2026
This was fixed in #49937