[ARROW-10121] [C++][Python] Variable dictionaries do not survive roundtrip to IPC stream

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 2.0.0
• Component/s: C++, Python
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/26133
• Assignee: Antoine Pitrou
• Reporter: Wes McKinney
• Created: 28/Sep/20 17:26
• Updated: 11/Jan/23 08:11
• Resolved: 05/Oct/20 20:40

Description

Failing test case (from dev@ https://lists.apache.org/thread.html/r338942b4e9f9316b48e87aab41ac49c7ffedd45733d4a6349523b7eb%40%3Cdev.arrow.apache.org%3E)

import pyarrow as pa
from io import BytesIO

pa.__version__

schema = pa.schema([pa.field('foo', pa.int32()), pa.field('bar', pa.dictionary(pa.int32(), pa.string()))] )
r1 = pa.record_batch(
    [
        [1, 2, 3, 4, 5],
        pa.array(["a", "b", "c", "d", "e"]).dictionary_encode()
    ],
    schema
)

r1.validate()
r2 = pa.record_batch(
    [
        [1, 2, 3, 4, 5],
        pa.array(["c", "c", "e", "f", "g"]).dictionary_encode()
    ],
    schema
)

r2.validate()

assert r1.column(1).dictionary != r2.column(1).dictionary


sink =  pa.BufferOutputStream()
writer = pa.RecordBatchStreamWriter(sink, schema)

writer.write(r1)
writer.write(r2)

serialized = BytesIO(sink.getvalue().to_pybytes())
stream = pa.ipc.open_stream(serialized)

deserialized = []

while True:
    try:
        deserialized.append(stream.read_next_batch())
    except StopIteration:
        break

assert deserialized[1][1].to_pylist() == r2[1].to_pylist()

Issue Links

• links to: GitHub Pull Request #8302