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  1. MariaDB ColumnStore
  2. MCOL-4783

Propagate LIMIT into TupleBPS to reduce the number of simultaneous Primitive Jobs issued by TBPS

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    Details

    • Type: New Feature
    • Status: Open (View Workflow)
    • Priority: Major
    • Resolution: Unresolved
    • Affects Version/s: 6.1.1
    • Fix Version/s: 6.3.1
    • Component/s: ExeMgr
    • Labels:
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      Description

      As of 6.1.1 TupleBPS::sendJobs() sends out JobList.MaxOutstandingRequests(20 extents of work by default) * 1024 Primitive Jobs simultaneously. By default it worths 20 extents of columnar data.
      In case of queries like SELECT * FROM table_with_500_columns LIMIT 1 this overwhelms PPs with needless work and spoils the buffer cache. The optimizer must propagate the LIMIT into TupleBPS so that it issues a limited number of outstanding Primitive jobs for queries where it is semantically possible.

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            Assignee:
            Unassigned Unassigned
            Reporter:
            drrtuy Roman
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              Updated:

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