Julian de Ruiter created ARROW-5666:
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Summary: [Python] Underscores in partition (string) values are
dropped when reading dataset
Key: ARROW-5666
URL: https://issues.apache.org/jira/browse/ARROW-5666
Project: Apache Arrow
Issue Type: Bug
Components: Python
Affects Versions: 0.13.0
Reporter: Julian de Ruiter
When reading a partitioned dataset, in which the partition column contains
string values with underscores, pyarrow seems to be ignoring the underscores in
the resulting values.
For example if I write and then read a dataset as follows:
{code:java}
import pyarrow as pa
import pandas as pd
df = pd.DataFrame({
"year_week": ["2019_2", "2019_3"],
"value": [1, 2]
})
table = pa.Table.from_pandas(df.head())
pq.write_to_dataset(table, 'test', partition_cols=["year_week"])
table2 = pq.ParquetDataset('test').read()
{code}
The resulting 'year_week' column in table 2 has lost the underscores:
{code:java}
table2[1] # Gives:
<Column name='year_week' type=DictionaryType(dictionary<values=int64,
indices=int32, ordered=0>)>
[
-- dictionary:
[
20192,
20193
]
-- indices:
[
0
],
-- dictionary:
[
20192,
20193
]
-- indices:
[
1
]
]
{code}
Is this intentional behaviour or is this a bug in arrow?
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