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Posted to issues-all@impala.apache.org by "Tim Armstrong (JIRA)" <ji...@apache.org> on 2018/04/30 16:20:00 UTC

[jira] [Resolved] (IMPALA-6680) Consider reserving max 2 I/O buffers per Parquet column when there are multiple columns

     [ https://issues.apache.org/jira/browse/IMPALA-6680?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tim Armstrong resolved IMPALA-6680.
-----------------------------------
    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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