[jira] [Updated] (ARROW-13798) [Python] Selective projection of struct fields errors with use_legacy_dataset = False

["Raúl Cumplido (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-13798?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Raúl Cumplido updated ARROW-13798:
----------------------------------
    Fix Version/s: 11.0.0
                       (was: 10.0.0)

> [Python] Selective projection of struct fields errors with use_legacy_dataset = False
> -------------------------------------------------------------------------------------
>
>                 Key: ARROW-13798
>                 URL: https://issues.apache.org/jira/browse/ARROW-13798
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Parquet, Python
>    Affects Versions: 5.0.0
>         Environment: Python 3.6.9
>            Reporter: Mark Grey
>            Priority: Critical
>              Labels: columns, parquet, python
>             Fix For: 11.0.0
>
>
> Selectively projecting fields from within a struct when reading from parquet files triggers an {{ArrowInvalid}} error when using the new dataset api ({{use_legacy_dataset=False}}).  Passing {{use_legacy_dataset=True}} yields the expected behavior: loading only the columns enumerated in the {{columns}} argument, recursing into structs if there is a {{.}} delimeter in the field name.
> Using the following test table:
> {code:python}
> df = pd.DataFrame({
>     'user_id': ['abc123', 'qrs456'],
>     'interaction': [{'type': 'click', 'element': 'button'}, {'type':'scroll', 'element': 'window'}]
> })
> table = pa.Table.from_pandas(df)
> pq.write_table(table, 'example.parquet')
> {code}
> Using the current default datasets API:
> {code:python}
> table_latest = pq.read_table('example.parquet', columns = ['user_id', 'interaction.type'])
> {code}
> yields:
> {noformat}
> ---------------------------------------------------------------------------
> ArrowInvalid                              Traceback (most recent call last)
> <ipython-input-25-982ca2d96075> in <module>
> ----> 1 table_latest = pq.read_table('/'.join([out_path, 'example.parquet']), columns = ['user_id', 'interaction.type'], filesystem = fs)
>       2 table_latest
> /usr/local/share/sciencebox/venv/lib/python3.6/site-packages/pyarrow/parquet.py in read_table(source, columns, use_threads, metadata, use_pandas_metadata, memory_map, read_dictionary, filesystem, filters, buffer_size, partitioning, use_legacy_dataset, ignore_prefixes, pre_buffer, coerce_int96_timestamp_unit)
>    1894 
>    1895         return dataset.read(columns=columns, use_threads=use_threads,
> -> 1896                             use_pandas_metadata=use_pandas_metadata)
>    1897 
>    1898     if ignore_prefixes is not None:
> /usr/local/share/sciencebox/venv/lib/python3.6/site-packages/pyarrow/parquet.py in read(self, columns, use_threads, use_pandas_metadata)
>    1744         table = self._dataset.to_table(
>    1745             columns=columns, filter=self._filter_expression,
> -> 1746             use_threads=use_threads
>    1747         )
>    1748 
> /usr/local/share/sciencebox/venv/lib/python3.6/site-packages/pyarrow/_dataset.pyx in pyarrow._dataset.Dataset.to_table()
> /usr/local/share/sciencebox/venv/lib/python3.6/site-packages/pyarrow/_dataset.pyx in pyarrow._dataset.Dataset.scanner()
> /usr/local/share/sciencebox/venv/lib/python3.6/site-packages/pyarrow/_dataset.pyx in pyarrow._dataset.Scanner.from_dataset()
> /usr/local/share/sciencebox/venv/lib/python3.6/site-packages/pyarrow/_dataset.pyx in pyarrow._dataset._populate_builder()
> /usr/local/share/sciencebox/venv/lib/python3.6/site-packages/pyarrow/error.pxi in pyarrow.lib.check_status()
> ArrowInvalid: No match for FieldRef.Name(interaction.type) in user_id: string
> interaction: struct<element: string, type: string>{noformat}
> Whereas: 
> {code:python}
> table_legacy = pq.read_table('example.parquet', columns = ['user_id', 'interaction.type'], use_legacy_dataset = True)
> {code}
> Yields:
> {noformat}
> pyarrow.Table
> user_id: string
> interaction: struct<type: string>
>   child 0, type: string{noformat}



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