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Posted to jira@arrow.apache.org by "ASF GitHub Bot (Jira)" <ji...@apache.org> on 2021/04/19 17:23:00 UTC

[jira] [Updated] (ARROW-12386) [C++] Support file parallelism in AsyncScanner

     [ https://issues.apache.org/jira/browse/ARROW-12386?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

ASF GitHub Bot updated ARROW-12386:
-----------------------------------
    Labels: pull-request-available  (was: )

> [C++] Support file parallelism in AsyncScanner
> ----------------------------------------------
>
>                 Key: ARROW-12386
>                 URL: https://issues.apache.org/jira/browse/ARROW-12386
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Weston Pace
>            Assignee: Weston Pace
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Whether we pull from files in parallel or not is controlled by how we merge the batch streams in `AsyncScanner::ScanBatchesUnorderedAsync`.  Currently we are relying on `MakeConcatenatedGenerator` which is incorrect.  This is needed because `MakeMergedGenerator` pulls from its source (an `EnumeratingGenerator`) in an async reentrant fashion.  `MakeMergedGenerator` should not do this.  If some kind of readahead is truly necessary there then use `MakeReadaheadGenerator`.



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