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  1. MariaDB Server
  2. MDEV-383

Evaluate subquery predicates earlier or later depending on their SELECTIVITY

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      (Based on conversation with Igor)
      There are a lot of subquery conditions out there that are inexpensive to
      evaluate and have good selectivity.

      If we just implement MDEV-83, we may get regressions. We need to take
      subquery condition's selectivity into account.

      It is difficult to get a meaningful estimate for an arbitrary, correlated
      subquery predicate.

      One possible solution is to measure selectivity during execution and reattach
      predicates on the fly.

      We don't want to change the query plan all the time, one way to dynamically
      move items between item trees is to wrap them inside Item_func_trig_cond so
      we can switch them on and off.

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              Assignee:
              igor Igor Babaev
              Reporter:
              psergey Sergei Petrunia
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              3 Vote for this issue
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                Created:
                Updated: