[jira] [Commented] (ARROW-10480) [Python] Parquet write_table creates gzipped Parquet file, not Parquet with gzip compression

["David Li (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-10480?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17227033#comment-17227033 ] 

David Li commented on ARROW-10480:
----------------------------------

I believe this is due to [a56e483126|https://github.com/apache/arrow/commit/a56e483126] where ParquetWriter now uses open_output_stream instead of open for non-legacy filesystems; the former detects a compression method by looking at the file extension. Furthermore, passing a legacy filesystem explicitly doesn't fix it, because pyarrow.fs._ensure_filesystem maps the legacy ones to new ones.

[~jorisvandenbossche] what do you think? We often use filenames with .parquet.snappy or .snappy.parquet, the former of which now gets tripped up - but not sure if that's common to do.

> [Python] Parquet write_table creates gzipped Parquet file, not Parquet with gzip compression
> --------------------------------------------------------------------------------------------
>
>                 Key: ARROW-10480
>                 URL: https://issues.apache.org/jira/browse/ARROW-10480
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Python
>    Affects Versions: 2.0.0
>            Reporter: David Li
>            Priority: Major
>             Fix For: 2.0.1
>
>
> Writing "foo.parquet.gz" in Arrow 2.0.0 creates a gzipped Parquet file, which Arrow can't read back, while in 1.0.1 it created a Parquet file with gzip compression. Hence I think this is a regression.
> In Arrow 2.0.0:
> {noformat}
> > pip freeze
> numpy==1.19.4
> pyarrow==2.0.0
> > python write.py
> Arrow: 2.0.0
> Read/write with PyArrow:
> test.pyarrow.gz: gzip compressed data, from Unix, original size modulo 2^32 630
> Traceback (most recent call last):
>   File "write.py", line 12, in <module>
>     print(pq.read_table("test.pyarrow.gz"))
>   File "/home/lidavidm/Code/twosigma/arrow-regression/venv/lib/python3.8/site-packages/pyarrow/parquet.py", line 1607, in read_table
>     dataset = _ParquetDatasetV2(
>   File "/home/lidavidm/Code/twosigma/arrow-regression/venv/lib/python3.8/site-packages/pyarrow/parquet.py", line 1452, in __init__
>     [fragment], schema=fragment.physical_schema,
>   File "pyarrow/_dataset.pyx", line 761, in pyarrow._dataset.Fragment.physical_schema.__get__
>   File "pyarrow/error.pxi", line 122, in pyarrow.lib.pyarrow_internal_check_status
>   File "pyarrow/error.pxi", line 99, in pyarrow.lib.check_status
> OSError: Could not open parquet input source 'test.pyarrow.gz': Invalid: Parquet magic bytes not found in footer. Either the file is corrupted or this is not a parquet file. {noformat}
> But in Arrow 1.0.1:
> {noformat}
> > pip freeze
> numpy==1.19.4
> pyarrow==1.0.1
> > python write.py
> Arrow: 1.0.1
> Read/write with PyArrow:
> test.pyarrow.gz: Apache Parquet
> pyarrow.Table
> ints: int64 {noformat}
> Reproduction:
> {code:python}
> import pyarrow as pa
> import pyarrow.parquet as pq
> import subprocess
> print("Arrow:", pa.__version__)
> print()
> print("Read/write with PyArrow:")
> table = pa.table([pa.array(range(4))], names=["ints"])
> pq.write_table(table, "test.pyarrow.gz", compression="GZIP")
> subprocess.check_call(["file", "test.pyarrow.gz"])
> print(pq.read_table("test.pyarrow.gz"))
> {code}
>  



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