Commit 09c3e18f authored by unknown's avatar unknown
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BUG#10037: A proper fix: Add 0.01 to cost of 'range' scans, don't add 0.01 to... 

BUG#10037: A proper fix: Add 0.01 to cost of 'range' scans, don't add 0.01 to cost of the 'index' scan.
parent ee5d8be5

sql/opt_range.cc

+11 −6
Original line number Diff line number Diff line
@@ -2257,8 +2257,7 @@ inline double get_index_only_read_time(const PARAM* param, ha_rows records, 
			 param->table->file->ref_length) + 1);

  read_time=((double) (records+keys_per_block-1)/

             (double) keys_per_block);

  /* Add 0.01 to avoid cost races between 'range' and 'index' */

  return read_time + 0.01;

  return read_time;

}
@@ -3150,10 +3149,16 @@ static TRP_RANGE *get_key_scans_params(PARAM *param, SEL_TREE *tree, 
          (param->table->file->index_flags(keynr, param->max_key_part,1) &

           HA_KEYREAD_ONLY) &&

          !(pk_is_clustered && keynr == param->table->s->primary_key))

        /* We can resolve this by only reading through this key. */

      {

        /*

          We can resolve this by only reading through this key. 

          0.01 is added to avoid races between range and 'index' scan.

        */

        found_read_time= get_index_only_read_time(param,found_records,keynr) +

                         cpu_cost;

                         cpu_cost + 0.01;

      }

      else

      {

        /*

          cost(read_through_index) = cost(disk_io) + cost(row_in_range_checks)

          The row_in_range check is in QUICK_RANGE_SELECT::cmp_next function.
@@ -3161,8 +3166,8 @@ static TRP_RANGE *get_key_scans_params(PARAM *param, SEL_TREE *tree, 
	found_read_time= param->table->file->read_time(keynr,

                                                       param->range_count,

                                                       found_records) +

			 cpu_cost;



			 cpu_cost + 0.01;

      }

      DBUG_PRINT("info",("key %s: found_read_time: %g (cur. read_time: %g)",

                         param->table->key_info[keynr].name, found_read_time,

                         read_time));