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FIxed bug #14927.

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A query with a group by and having clauses could return a wrong
result set if the having condition contained a constant conjunct 
evaluated to FALSE.
It happened because the pushdown condition for table with
grouping columns lost its constant conjuncts.
Pushdown conditions are always built by the function make_cond_for_table
that ignores constant conjuncts. This is apparently not correct when
constant false conjuncts are present.
This commit is contained in:
igor@rurik.mysql.com
2006-01-31 21:48:32 -08:00
parent 7e5108392d
commit d6370b48a7
6 changed files with 57 additions and 11 deletions
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17
mysql-test/r/having.result
View File

@ -141,3 +141,20 @@ SUM(a)
6
4
DROP TABLE t1;
CREATE TABLE t1 (a int);
INSERT INTO t1 VALUES (1), (2), (1), (3), (2), (1);
SELECT a FROM t1 GROUP BY a HAVING a > 1;
a
2
3
SELECT a FROM t1 GROUP BY a HAVING 1 != 1 AND a > 1;
a
SELECT 0 AS x, a FROM t1 GROUP BY x,a HAVING x=1 AND a > 1;
x a
EXPLAIN SELECT a FROM t1 GROUP BY a HAVING 1 != 1 AND a > 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible HAVING
EXPLAIN SELECT 0 AS x, a FROM t1 GROUP BY x,a HAVING x=1 AND a > 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible HAVING
DROP table t1;

16
mysql-test/t/having.test
View File

@ -135,4 +135,20 @@ SELECT SUM(a) FROM t1 GROUP BY a HAVING SUM(a);
DROP TABLE t1;
#
# Bug #14927: HAVING clause containing constant false conjunct
#
CREATE TABLE t1 (a int);
INSERT INTO t1 VALUES (1), (2), (1), (3), (2), (1);
SELECT a FROM t1 GROUP BY a HAVING a > 1;
SELECT a FROM t1 GROUP BY a HAVING 1 != 1 AND a > 1;
SELECT 0 AS x, a FROM t1 GROUP BY x,a HAVING x=1 AND a > 1;
EXPLAIN SELECT a FROM t1 GROUP BY a HAVING 1 != 1 AND a > 1;
EXPLAIN SELECT 0 AS x, a FROM t1 GROUP BY x,a HAVING x=1 AND a > 1;
DROP table t1;
# End of 4.1 tests

2
sql/sql_lex.cc
View File

@ -1074,6 +1074,7 @@ void st_select_lex::init_query()
item_list.empty();
join= 0;
where= 0;
having= 0;
olap= UNSPECIFIED_OLAP_TYPE;
having_fix_field= 0;
resolve_mode= NOMATTER_MODE;
@ -1081,6 +1082,7 @@ void st_select_lex::init_query()
ref_pointer_array= 0;
select_n_having_items= 0;
prep_where= 0;
prep_having= 0;
subquery_in_having= explicit_limit= 0;
parsing_place= NO_MATTER;
is_item_list_lookup= 0;

1
sql/sql_lex.h
View File

@ -421,6 +421,7 @@ public:
char *db, *db1, *table1, *db2, *table2; /* For outer join using .. */
Item *where, *having; /* WHERE & HAVING clauses */
Item *prep_where; /* saved WHERE clause for prepared statement processing */
Item *prep_having;/* saved HAVING clause for prepared statement processing */
enum olap_type olap;
SQL_LIST table_list, group_list; /* FROM & GROUP BY clauses */
List<Item> item_list; /* list of fields & expressions */

10
sql/sql_prepare.cc
View File

@ -1665,10 +1665,11 @@ int mysql_stmt_prepare(THD *thd, char *packet, uint packet_length,
for (; sl; sl= sl->next_select_in_list())
{
/*
Save WHERE clause pointers, because they may be changed
Save WHERE, HAVING clause pointers, because they may be changed
during query optimisation.
*/
sl->prep_where= sl->where;
sl->prep_having= sl->having;
/*
Switch off a temporary flag that prevents evaluation of
subqueries in statement prepare.
@ -1694,13 +1695,18 @@ static void reset_stmt_for_execute(Prepared_statement *stmt)
/* remove option which was put by mysql_explain_union() */
sl->options&= ~SELECT_DESCRIBE;
/*
Copy WHERE clause pointers to avoid damaging they by optimisation
Copy WHERE, HAVING clause pointers to avoid damaging they by optimisation
*/
if (sl->prep_where)
{
sl->where= sl->prep_where->copy_andor_structure(thd);
sl->where->cleanup();
}
if (sl->prep_having)
{
sl->having= sl->prep_having->copy_andor_structure(thd);
sl->having->cleanup();
}
DBUG_ASSERT(sl->join == 0);
ORDER *order;
/* Fix GROUP list */

14
sql/sql_select.cc
View File

@ -501,13 +501,19 @@ JOIN::optimize()
DBUG_RETURN(1);
}
if (cond_value == Item::COND_FALSE ||
{
Item::cond_result having_value;
having= optimize_cond(thd, having, &having_value);
if (cond_value == Item::COND_FALSE || having_value == Item::COND_FALSE ||
(!unit->select_limit_cnt && !(select_options & OPTION_FOUND_ROWS)))
{ /* Impossible cond */
zero_result_cause= "Impossible WHERE";
zero_result_cause= having_value == Item::COND_FALSE ?
"Impossible HAVING" : "Impossible WHERE";
error= 0;
DBUG_RETURN(0);
}
}
/* Optimize count(*), min() and max() */
if (tables_list && tmp_table_param.sum_func_count && ! group_list)
@ -4611,10 +4617,8 @@ optimize_cond(THD *thd, COND *conds, Item::cond_result *cond_value)
DBUG_EXECUTE("info", print_where(conds, "after remove"););
}
else
{
*cond_value= Item::COND_TRUE;
select->prep_where= 0;
}
DBUG_RETURN(conds);
}