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Posted to issues@impala.apache.org by "Tim Armstrong (Jira)" <ji...@apache.org> on 2020/01/22 21:25:00 UTC

[jira] [Created] (IMPALA-9317) Improve number of instances estimate for scans in planner

Tim Armstrong created IMPALA-9317:
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             Summary: Improve number of instances estimate for scans in planner
                 Key: IMPALA-9317
                 URL: https://issues.apache.org/jira/browse/IMPALA-9317
             Project: IMPALA
          Issue Type: Improvement
          Components: Frontend
            Reporter: Tim Armstrong


Currently the number of instances (used for various estimates) is calculated as estimated # hosts * mt_dop. This is suboptimal, because in many cases there isn't enough input data to allow creating that many instances per host.

The per-host estimate for scans actually already handles this correctly by capping the hosts estimate at the number of input splits - we should use the same approach for number of instance estimates.



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