[MDEV-32732] Support DESC indexes in loose scan optimization Created: 2023-11-08  Updated: 2023-12-22

Status: Open
Project: MariaDB Server
Component/s: Optimizer
Fix Version/s: 11.5

Type: Task Priority: Major
Reporter: Sergei Petrunia Assignee: Unassigned
Resolution: Unresolved Votes: 0
Labels: optimizer-easy, optimizer-feature

Issue Links:
Relates
relates to MDEV-27576 Use DESC indexes for MIN/MAX optimiza... Closed

 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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