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  1. MariaDB Server
  2. MDEV-8954

unnecessary fetch of entire table

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    • Sprint:
      2017-02, 10.1.22

      Description

      set global optimizer_switch="engine_condition_pushdown=on"

      Ouch! It is now pulling back the entire table 200 rows at a time.

      Query: SELECT DISTINCT x FROM table
      PRIMARY KEY (x,y,z)
      Backend queries: SELECT x FROM table x > 12345 ORDER BY x,y,z LIMIT 200.

      (And it is taking ​much​ longer than when ecp=OFF)

      Question 1: Why fetch the table rather than executing the query?

      Question 2: When you have a multi-part PK, that code is likely to be "wrong". Note that it always compared only x, not y and z. And it always said 200.

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              Assignee:
              jacob-mathew Jacob Mathew (Inactive)
              Reporter:
              rjasdf Rick James (Inactive)
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