diff options
Diffstat (limited to 'sql/sql_select.cc')
| -rw-r--r-- | sql/sql_select.cc | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 1d11f23d854..b519c06420f 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -3658,7 +3658,7 @@ update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab, { KEYUSE key_end,*prev,*save_pos,*use; - qsort(keyuse->buffer,keyuse->elements,sizeof(KEYUSE), + my_qsort(keyuse->buffer,keyuse->elements,sizeof(KEYUSE), (qsort_cmp) sort_keyuse); bzero((char*) &key_end,sizeof(key_end)); /* Add for easy testing */ @@ -4371,8 +4371,9 @@ choose_plan(JOIN *join, table_map join_tables) Apply heuristic: pre-sort all access plans with respect to the number of records accessed. */ - qsort(join->best_ref + join->const_tables, join->tables - join->const_tables, - sizeof(JOIN_TAB*), straight_join?join_tab_cmp_straight:join_tab_cmp); + my_qsort(join->best_ref + join->const_tables, + join->tables - join->const_tables, sizeof(JOIN_TAB*), + straight_join ? join_tab_cmp_straight : join_tab_cmp); if (straight_join) { @@ -4421,6 +4422,17 @@ choose_plan(JOIN *join, table_map join_tables) ptr1 pointer to first JOIN_TAB object ptr2 pointer to second JOIN_TAB object + NOTES + The order relation implemented by join_tab_cmp() is not transitive, + i.e. it is possible to choose such a, b and c that (a < b) && (b < c) + but (c < a). This implies that result of a sort using the relation + implemented by join_tab_cmp() depends on the order in which + elements are compared, i.e. the result is implementation-specific. + Example: + a: dependent = 0x0 table->map = 0x1 found_records = 3 ptr = 0x907e6b0 + b: dependent = 0x0 table->map = 0x2 found_records = 3 ptr = 0x907e838 + c: dependent = 0x6 table->map = 0x10 found_records = 2 ptr = 0x907ecd0 + RETURN 1 if first is bigger -1 if second is bigger |