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  1. MariaDB Server
  2. MDEV-8456

Dead code in Item_cond::fix_fields() and Item_func_between::fix_fields()

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Details

    • Bug
    • Status: Closed (View Workflow)
    • Major
    • Resolution: Fixed
    • 10.0(EOL), 10.1(EOL)
    • 10.1.6
    • Optimizer
    • None

    Description

      Item_cond::fix_fields() and Item_func_between::fix_fields() update these optimizer related SELECT_LEX members:

      thd->lex->current_select->cond_count and
      thd->lex->current_select->between_count

      The purpose of these members is to allocate optimizer related buffers in:

      • update_ref_and_keys() in sql_select.cc and
      • check_func_dependency() in opt_table_elimination,cc
        and it seems they have no any other purposes..

      This looks like a dead code and the collected values are never used:

      • cond_count and_between_count are later always initialized to 0 before the walk(count_sargable_conds) call in update_ref_and_keys().
      • moreover, using the values collected during fix_fields() would not be correct to allocate optimized related buffers, because the code in fix_fields() does not distinguish between different query parts, so the items can be just a part of the SELECT list rather than a part of WHERE/HAVING/ON.

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            bar Alexander Barkov
            bar Alexander Barkov
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            Dates

              Created:
              Updated:
              Resolved:

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