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https://issues.apache.org/jira/browse/ARROW-14648?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vibhatha Lakmal Abeykoon reassigned ARROW-14648:
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Assignee: Vibhatha Lakmal Abeykoon
> [C++][Dataset] Change scanner readahead limits to be based on bytes instead
> of number of batches
> ------------------------------------------------------------------------------------------------
>
> Key: ARROW-14648
> URL: https://issues.apache.org/jira/browse/ARROW-14648
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Weston Pace
> Assignee: Vibhatha Lakmal Abeykoon
> Priority: Major
> Labels: datasets, query-engine
>
> In the scanner readahead is controlled by "batch_readahead" and
> "fragment_readahead" (both specified in the scan options). This was mainly
> motivated on my work with CSV and the defaults of 32 and 8 will cause the
> scanner to buffer ~256MB of data (given the default block size of 1MB).
> For parquet / IPC this would mean we are buffering 256 row groups which is
> entirely too high.
> Rather than make users figure out complex parameters we should have a single
> readahead limit that is specified in bytes.
> This will be "best effort". I'm not suggest we support partial reads of row
> groups / record batches so if the limit is set very small we still might end
> up with more in RAM just because we can only load entire row groups.
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