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BUG#14940: post-review fixes

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sergefp@mysql.com 2006-07-30 00:02:09 +04:00
parent 699291a8e6
commit cbd57af8ed
1 changed files with 8 additions and 6 deletions
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14
sql/opt_range.cc
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@ -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",