[
https://issues.apache.org/jira/browse/ARROW-5666?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Wes McKinney reassigned ARROW-5666:
-----------------------------------
Assignee: Joris Van den Bossche
> [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
> Assignee: Joris Van den Bossche
> Priority: Major
> Labels: dataset-parquet-read, parquet
>
> 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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