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  1. IMPALA
  2. IMPALA-9792

Split Kudu scan ranges into smaller chunks for greater paralellelism

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    Details

    • Type: Improvement
    • Status: Open
    • Priority: Major
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: Backend

      Description

      We currently use one thread to scan each tablet, which may underparallelise queries in many cases. Kudu added an API in KUDU-2437 and KUDU-2670 to split tokens at a finer granularity.

      See
      https://github.com/apache/kudu/commit/22a6faa44364dec3a171ec79c15b814ad9277d8f#diff-a4afa9dba99c7612b2cb9176134ff2b0

      The major downside is that the planner has to do an extra RPC to a tserver for each tablet being scanned in order to figure out key range splits. Maybe we can tie this to mt_dop >= 2, or use some heuristics to avoid these RPCs for smaller tables.

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              • Assignee:
                bikramjeet.vig Bikramjeet Vig
                Reporter:
                tarmstrong Tim Armstrong
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                • Created:
                  Updated: