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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

    • Type: Bug
    • Status: Closed (View Workflow)
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 10.1, 10.0
    • Fix Version/s: 10.1.6
    • Component/s: Optimizer
    • Labels:
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      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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            Assignee:
            bar Alexander Barkov
            Reporter:
            bar Alexander Barkov
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              Updated:
              Resolved: