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https://issues.apache.org/jira/browse/IMPALA-6680?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tim Armstrong resolved IMPALA-6680.
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Resolution: Later
This might still be reasonable but isn't essential to IMPALA-4835. Can revisit
later.
> Consider reserving max 2 I/O buffers per Parquet column when there are
> multiple columns
> ---------------------------------------------------------------------------------------
>
> Key: IMPALA-6680
> URL: https://issues.apache.org/jira/browse/IMPALA-6680
> Project: IMPALA
> Issue Type: Sub-task
> Components: Backend
> Affects Versions: Not Applicable
> Reporter: Tim Armstrong
> Assignee: Tim Armstrong
> Priority: Major
> Labels: resource-management
>
> Reserving 3 * 8MB per column to get triple buffering is minimally useful
> except in the case when you're scanning a single very large column. 2 * 8MB
> is enough to overlap compute and I/O, and if you have multiple large columns
> that will mean that there are multiple I/Os in flight in almost all cases.
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