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  1. MariaDB Server
  2. MDEV-32732

Support DESC indexes in loose scan optimization

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    Description

      Group-min-max (aka Loose Scan) optimization does not work for reverse-ordered indexes:

      looking in opt_range.cc one can see in get_best_group_min_max() :

            for (uint i= 0; i < table->actual_n_key_parts(cur_index_info); i++)
      		 
            {
      		 
              if (cur_index_info->key_part[i].key_part_flag & HA_REVERSE_SORT)
      		 
              {
      		 
                cause="Reverse-ordered (not supported yet)";
      		 
                goto next_index;
      		 
              }
      		 
            }

      This task is to support it.

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          relates to

          Task - A task that needs to be done. MDEV-27576 Use DESC indexes for MIN/MAX optimization

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

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              ycp Yuchen Pei
              psergei Sergei Petrunia
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                Updated:

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