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FIxed bug #14927.

Browse Source 
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.


mysql-test/r/having.result:
  Added A test case for bug #14927.
mysql-test/t/having.test:
  Added A test case for bug #14927.
sql/sql_lex.cc:
  Fixed bug #14927.
  Initialized fields for having conditions in  st_select_lex::init_query().
sql/sql_lex.h:
  Fixed bug #14927.
  Added a field to restore having condititions for execution in SP and PS.
sql/sql_prepare.cc:
  Fixed bug #14927.
  Added code to restore havinf conditions for execution in SP and PS.
sql/sql_select.cc:
  Fixed bug #14927.
  Performed evaluation of constant expressions in having clauses.
  If the having condition contains a constant conjunct that is always false
  an empty result set is returned after the optimization phase.
  In this case the corresponding EXPLAIN command now returns 
  "Impossible HAVING" in the last column.
This commit is contained in:
unknown
2006-01-31 21:48:32 -08:00
parent 97deac8b8c
commit a400e7feb9
6 changed files with 57 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

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);
}