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  1. MariaDB Server
  2. MDEV-6480

Remove conditions for which range optimizer returned SEL_ARG::IMPOSSIBLE.

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    Description

      This task is a "cut the Gordian Knot" approach to solving the problem described in two comments here:

      https://jira.mariadb.org/browse/MDEV-6454?focusedCommentId=55355&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-55355

      https://jira.mariadb.org/browse/MDEV-6454?focusedCommentId=55358&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-55358

      The idea is that as soon as range optimizer concludes that some for Item* (possibly inside an OR) we have produced a tree of type SEL_ARG::IMPOSSIBLE, that Item* should be removed from the WHERE condition.

      The will solve the problem described in the above two comments, and also will open additional optimization possibilities.

      Challenges to explore

      • How does one remove Item* from the WHERE in a PS-safe way (call thd->change_item_tree() or ... ?)
      • Do we need to do AND/OR flattening after such conversion?

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          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-6454 Performance degradation (suboptimal execution plan) on a query with expected range access

          • Major - Major loss of function.
          • Closed

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              psergei Sergei Petrunia
              psergei Sergei Petrunia
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                Resolved:

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