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  1. MariaDB Server
  2. MDEV-26974

Improve selectivity and related costs in optimizer

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    Details

    • Type: Task
    • Status: In Testing (View Workflow)
    • Priority: Critical
    • Resolution: Unresolved
    • Fix Version/s: 11.0
    • Component/s: Optimizer
    • Labels:
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      Description

      There is a cleanup task for several things in the optimizer.

      • Ensure that 0 <= selectivity <= 1
      • Ensure that selectivity calculation doesn't return too few row
      • Calculate and use index only cost when appropriate.
      • Examine and improve cost calculation in the optimizer for:
      • filters
      • Ensure that filter cost calculation also include index only cost and compare with WHERE
      • ranges
      • table scans
      • hash and joins and cached full joins
      • group by
      • Adjusted Range_rowid_filter_cost_info lookup cost for very small arrays.
      • Limit calculated rows to the number of rows in the table
      • Ensure that test_quick_select doesn't return more rows than in the table

      A lot of other optimizer related issues, documented at
      https://mariadb.com/kb/en/the-optimizer-cost-model-from-mariadb-11-0/

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              Assignee:
              elenst Elena Stepanova
              Reporter:
              monty Michael Widenius
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                Updated:

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