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https://issues.apache.org/jira/browse/ARROW-6796?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wes McKinney closed ARROW-6796.
-------------------------------
Resolution: Duplicate
Dup of ARROW-6060
> Certain moderately-sized (~100MB) default-Snappy-compressed Parquet files
> take enormous memory and long time to load by pyarrow.parquet.read_table
> --------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: ARROW-6796
> URL: https://issues.apache.org/jira/browse/ARROW-6796
> Project: Apache Arrow
> Issue Type: Bug
> Affects Versions: 0.14.1
> Reporter: V Luong
> Priority: Critical
> Fix For: 0.15.0
>
>
> My Spark workloads produce small-to-moderately-sized Parquet files with
> typical on-disk sizes in the order of 100-300MB, and I use PyArrow to process
> these files further.
> Surprisingly, I find that similarly-sized Parquet files sometimes take vastly
> different amounts of memory and time to load using
> pyarrow.parquet.read_table. For illustration, I've uploaded 2 such parquet
> files to s3://public-parquet-test-data/fast.snappy.parquet and
> s3://public-parquet-test-data/slow.snappy.parquet.
> Both files have about 1.2 million rows and 450 columns and occupy 100-120MB
> on disk. But when they are loaded by read_table:
> * fast.snappy.parquet takes 10-15GB of memory and 5-8s to load
> * slow.snappy.parquet takes up to 300GB (!!) of memory and 45-60s to load
> Since I have been using the default Snappy compression in all my Spark jobs,
> it is unlikely that the files differ in the their compression levels. That
> the on-disk sizes are similar suggests that they are similarly compressed. So
> the fact that slow.snappy.parquet takes 10-20x amounts of resources to read
> is very surprising.
> My benchmarking code snippet is below. I'd appreciate your help to
> troubleshoot this matter.
> ```{python}
> from pyarrow.parquet import read_metadata, read_table
> from time import time
> from tqdm import tqdm
>
>
> FAST_PARQUET_TMP_PATH = '/tmp/fast.snappy.parquet'
> SLOW_PARQUET_TMP_PATH = '/tmp/slow.snappy.parquet'
>
>
> fast_parquet_metadata = read_metadata(FAST_PARQUET_TMP_PATH)
> print('Fast Parquet Metadata: {}\n'.format(fast_parquet_metadata))
>
> durations = []
> for _ in tqdm(range(3)):
> tic = time()
> tbl = read_table(
> source=FAST_PARQUET_TMP_PATH,
> columns=None,
> use_threads=True,
> metadata=None,
> use_pandas_metadata=False,
> memory_map=False,
> filesystem=None,
> filters=None)
> toc = time()
> durations.append(toc-tic)
> print('Fast Parquet READ_TABLE(...) Durations: {}\n'
> .format(', '.join('{:.0f}s'.format(duration) for duration in
> durations)))
>
>
> slow_parquet_metadata = read_metadata(SLOW_PARQUET_TMP_PATH)
> print('Slow Parquet Metadata: {}\n'.format(slow_parquet_metadata))
>
> durations = []
> for _ in tqdm(range(3)):
> tic = time()
> tbl = read_table(
> source=SLOW_PARQUET_TMP_PATH,
> columns=None,
> use_threads=True,
> metadata=None,
> use_pandas_metadata=False,
> memory_map=False,
> filesystem=None,
> filters=None)
> toc = time()
> durations.append(toc - tic)
> print('Slow Parquet READ_TABLE(...) Durations: {}\n'
> .format(', '.join('{:.0f}s'.format(duration) for duration in
> durations)))
> ```
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