[jira] [Created] (PARQUET-1888) Provide guidance on number of file descriptors needed to read Parquet file

["Adam Shirey (Jira)" <ji...@apache.org>]

Adam Shirey created PARQUET-1888:
------------------------------------

             Summary: Provide guidance on number of file descriptors needed to read Parquet file
                 Key: PARQUET-1888
                 URL: https://issues.apache.org/jira/browse/PARQUET-1888
             Project: Parquet
          Issue Type: Task
         Environment: {code:bash}
$ rustc --version
rustc 1.47.0-nightly (6c8927b0c 2020-07-26)
{code}
Cargo.toml:
{code:yaml}
[dependencies]
parquet = "0.17"
rayon = "1.1"
...
{code}
            Reporter: Adam Shirey


I have a series of Parquet files that are 181 columns wide, and I'm processing them in parallel (using [rayon|https://github.com/rayon-rs/rayon/]). I ran into the OS limit (default 1024 according to {{ulimit -n}}) of open file descriptors when doing this, but each file was consuming 208 descriptors.

Is there a deterministic calculation for how many file descriptors will be used to process files so that one can determine appropriate multithreading in a situation like this?



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