Commit 3e2af0b8 authored by unknown's avatar unknown
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BUG#14940: post-review fixes 


sql/opt_range.cc:
  BUG#14940: post-review fixes:
   - fix comments
   - use set_if_smaller
parent ef452e19

sql/opt_range.cc

+8 −6
Original line number Diff line number Diff line
@@ -1872,14 +1872,17 @@ static int fill_used_fields_bitmap(PARAM *param) 
    correlations between sets of rows they will return.

    

    For example, if values of tbl.key1 and tbl.key2 are independent (a right

    assumption if we have no infromation about their correlation) then the

    assumption if we have no information about their correlation) then the

    correct estimate will be:

    

      E(#rows("tbl.key1 < c1 AND tbl.key2 < c2")) = 

      = E(#rows(tbl.key1 < c1)) / total_rows(tbl) * E(#rows(tbl.key2 < c2) / 

        total_rows(tbl).

      = E(#rows(tbl.key1 < c1)) / total_rows(tbl) * E(#rows(tbl.key2 < c2)



    which is smaller than MIN(rows(tbl.key1 < c1), rows(tbl.key2 < c2)).

    which is smaller than 

      

       MIN(E(#rows(tbl.key1 < c1), E(#rows(tbl.key2 < c2)))



    which is currently produced.



  TODO

   * Change the value returned in quick_condition_rows from a pessimistic
@@ -4469,8 +4472,7 @@ TRP_ROR_INTERSECT *get_best_covering_ror_intersect(PARAM *param, 
  trp->read_cost= total_cost;

  trp->records= records;

  trp->cpk_scan= NULL;

  if (records < param->table->quick_condition_rows)

     param->table->quick_condition_rows= records;

  set_if_smaller(param->table->quick_condition_rows, records); 



  DBUG_PRINT("info",

             ("Returning covering ROR-intersect plan: cost %g, records %lu",