[jira] [Updated] (ARROW-15045) PyArrow SIGSEGV error when using UnionDatasets

["Joris Van den Bossche (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-15045?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Joris Van den Bossche updated ARROW-15045:
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    Labels: dataset  (was: )

> PyArrow SIGSEGV error when using UnionDatasets
> ----------------------------------------------
>
>                 Key: ARROW-15045
>                 URL: https://issues.apache.org/jira/browse/ARROW-15045
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Python
>    Affects Versions: 6.0.1
>         Environment: Fedora Linux 35 (Workstation Edition), AMD Ryzen 5950X.
>            Reporter: Thomas Cercato
>            Priority: Blocker
>              Labels: dataset
>
> h3. The context:
> I am using PyArrow to read a folder structured as {{exchange/symbol/date.parquet}}. The folder contains multiple exchanges, multiple symbols and multiple files. At the time I am writing the folder is about 30GB/1.85M files.
> If I use a single PyArrow Dataset to read/manage the entire folder, the simplest process with just the dataset defined will occupy 2.3GB of RAM. The problem is, I am instanciating this dataset on multiple processes but since every process only needs some exchanges (typically just one), I don't need to read all folders and files in every single process.
> So I tried to use a UnionDataset composed of single exchange Dataset. In this way, every process just loads the required folder/files as a dataset. By a simple test, by doing so every process now occupy just 868MB of RAM, -63%.
> h3. The problem:
> When using a single Dataset for the entire folder/files, I have no problem at all. I can read filtered data without problems and it's fast as duck.
> But when I read the UnionDataset filtered data, I always get {{Process finished with exit code 139 (interrupted by signal 11: SIGSEGV}} error. So after looking every single source of the problem, I noticed that if I create a dummy folder with multiple exchanges but just some symbols, in order to limit the files amout to read, I don't get that error and it works normally. If I then copy new symbols folders (any) I get again that error.
> I came up thinking that the problem is not about my code, but linked instead to the amout of files that the UnionDataset is able to manage.
> Am I correct or am I doing something wrong? Thank you all, have a nice day and good work.



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