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https://issues.apache.org/jira/browse/ARROW-11400?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17324815#comment-17324815
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Joris Van den Bossche commented on ARROW-11400:
-----------------------------------------------
[~kszucs] is this re-milestoning done automatically? As I moved it back to
3.0.0, since this issue was fixed for 3.0.0
> [Python] Pickled ParquetFileFragment has invalid partition_expresion with
> dictionary type in pyarrow 2.0
> --------------------------------------------------------------------------------------------------------
>
> Key: ARROW-11400
> URL: https://issues.apache.org/jira/browse/ARROW-11400
> Project: Apache Arrow
> Issue Type: Bug
> Components: Python
> Reporter: Joris Van den Bossche
> Assignee: Joris Van den Bossche
> Priority: Minor
> Labels: dataset, pull-request-available
> Fix For: 4.0.0
>
> Time Spent: 1h 10m
> Remaining Estimate: 0h
>
> From https://github.com/dask/dask/pull/7066#issuecomment-767156623
> Simplified reproducer:
> {code:python}
> import pyarrow.parquet as pq
> import pyarrow.dataset as ds
> table = pa.table({'part': ['A', 'B']*5, 'col': range(10)})
> pq.write_to_dataset(table, "test_partitioned_parquet",
> partition_cols=["part"])
> # with partitioning_kwargs = {} there is no error
> partitioning_kwargs = {"max_partition_dictionary_size": -1}
> dataset = ds.dataset(
> "test_partitioned_parquet/", format="parquet",
> partitioning=ds.HivePartitioning.discover( **partitioning_kwargs)
> )
> frag = list(dataset.get_fragments())[0]
> {code}
> Querying this fragment works fine, but after serialization/deserialization
> with pickle, it gives errors (and with the original data example I actually
> got a segfault as well):
> {code}
> In [16]: import pickle
> In [17]: frag2 = pickle.loads(pickle.dumps(frag))
> In [19]: frag2.partition_expression
> ...
> UnicodeDecodeError: 'utf-8' codec can't decode byte 0xf1 in position 16:
> invalid continuation byte
> In [20]: frag2.to_table(schema=schema, columns=columns)
> Out[20]:
> pyarrow.Table
> col: int64
> part: dictionary<values=string, indices=int32, ordered=0>
> In [21]: frag2.to_table(schema=schema, columns=columns).to_pandas()
> ...
> ~/miniconda3/envs/arrow-20/lib/python3.8/site-packages/pyarrow/table.pxi in
> pyarrow.lib.table_to_blocks()
> ArrowException: Unknown error: Wrapping ɻ� failed
> {code}
> It seems the issue was specifically with a partition expression with
> dictionary type.
> Also when using an integer columns as the partition column, you get wrong
> values (but silently in this case):
> {code:python}
> In [42]: frag.partition_expression
> Out[42]:
> <pyarrow.dataset.Expression (part == [
> 1,
> 2
> ][0]:dictionary<values=int32, indices=int32, ordered=0>)>
> In [43]: frag2.partition_expression
> Out[43]:
> <pyarrow.dataset.Expression (part == [
> 170145232,
> 32754
> ][0]:dictionary<values=int32, indices=int32, ordered=0>)>
> {code}
> Now, it seems this is fixed in master. But since I don't remember it was
> fixed intentionally ([~bkietz]?), it would be good to add some tests for it.
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