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  1. MariaDB Server
  2. MDEV-20541

Implement a flag to show if an expression is non-deterministic

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    • Task
    • Status: Stalled (View Workflow)
    • Major
    • Resolution: Unresolved
    • None
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    Description

      Deterministic expression is an expression that doesn't use non-deterministic functions.
      Non-deterministic function is a function that for equal input sets returns the same result set.

      E.g.: LENGTH() function of VARCHAR fields.
      'a' = 'a '
      But
      LENGTH('a') = 1 != 2 = LENGTH('a ')

      So, for equal input variables LENGTH() function returns different results.
      Therefore, LENGTH() of VARCHARs is non-deterministic.

      This task is a subtask for MDEV-11588.
      Non-deterministic expressions of GROUP BY fields are not functionally dependent on GROUP BY fields. Therefore, can't be used in SELECT list, HAVING and ORDER BY clauses.

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              igor Igor Babaev
              shagalla Galina Shalygina (Inactive)
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