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https://issues.apache.org/jira/browse/ARROW-13161?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17368831#comment-17368831
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David Li commented on ARROW-13161:
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Thanks for clarifying. The sync scanner will be going away at some point, but
both the sync and async scanner have this issue. The sync scanner especially
would need refactoring in order to fix this issue, from what I see.
There's a {{batch_readahead}} parameter that would probably control this
better, but it's not actually hooked up to anything.
> Allow setting FragmentReadahead to 0 in ScannerBuilder
> ------------------------------------------------------
>
> Key: ARROW-13161
> URL: https://issues.apache.org/jira/browse/ARROW-13161
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Jayjeet Chakraborty
> Priority: Major
>
> I have an application where I need to set fragment readahead to 0. But, looks
> like for some reason the ScannerBuilder does not allow setting the fragment
> readahead to 0 [1]. It would be very helpful to know why it is that way and
> if a PR lifting that restriction would be accepted because a docstring
> mentions that users can set fragment readahead to 0 if they want [2].
> [1]https://github.com/apache/arrow/blob/master/cpp/src/arrow/dataset/scanner.cc#L864
> [2]https://github.com/apache/arrow/blob/998a2a1668ea57a49d85fbb38f7f0e7eb94c29db/cpp/src/arrow/dataset/scanner.h#L93
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