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Posted to issues@impala.apache.org by "Tim Armstrong (JIRA)" <ji...@apache.org> on 2018/03/15 22:12:00 UTC

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

Tim Armstrong created IMPALA-6680:
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             Summary: 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


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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