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Bug#56814 Explain + subselect + fulltext crashes server

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create_sort_index() function overwrites original JOIN_TAB::type field.
At re-execution of subquery overwritten JOIN_TAB::type(JT_ALL) is
used instead of JT_FT. It misleads test_if_skip_sort_order() and
the function tries to find suitable key for the order that should
not be allowed for FULLTEXT(JT_FT) table.
The fix is to restore JOIN_TAB strucures for subselect on re-execution
for EXPLAIN.
Additional fix:
Update TABLE::maybe_null field which
affects list_contains_unique_index() behaviour as it
could have the value(maybe_null==TRUE) based on the
assumption that this join is outer
(see setup_table_map() func).


mysql-test/r/explain.result:
  test case
mysql-test/t/explain.test:
  test case
sql/item_subselect.cc:
  Make subquery uncacheable in case of EXPLAIN. It allows to keep
  original JOIN_TAB::type(see JOIN::save_join_tab) and restore it
  on re-execution.
sql/sql_select.cc:
  -restore JOIN_TAB strucures for subselect on re-execution for EXPLAIN
  -Update TABLE::maybe_null field as it could have
   the value(maybe_null==TRUE) based on the assumption
   that this join is outer(see setup_table_map() func).
   This change is not related to the crash problem but
   affects EXPLAIN results in the test case.
This commit is contained in:
Sergey Glukhov 2010-10-18 16:12:27 +04:00
parent 127c721cef
commit d0ac4e2c5a
4 changed files with 106 additions and 5 deletions
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46
mysql-test/r/explain.result
View file

@ -251,4 +251,50 @@ EXPLAIN SELECT c1 FROM t1 WHERE c2 = 1 AND c4 = 1 AND c5 = 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref c2,c2_2 c2 10 const,const 3 Using where
DROP TABLE t1;
#
# Bug#56814 Explain + subselect + fulltext crashes server
#
CREATE TABLE t1(f1 VARCHAR(6) NOT NULL,
FULLTEXT KEY(f1),UNIQUE(f1));
INSERT INTO t1 VALUES ('test');
EXPLAIN SELECT 1 FROM t1
WHERE 1 > ALL((SELECT 1 FROM t1 JOIN t1 a ON (MATCH(t1.f1) AGAINST (""))
WHERE t1.f1 GROUP BY t1.f1));
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 system NULL NULL NULL NULL 1
2 SUBQUERY a system NULL NULL NULL NULL 1 Using filesort
2 SUBQUERY t1 fulltext f1 f1 0 1 Using where
PREPARE stmt FROM
'EXPLAIN SELECT 1 FROM t1
WHERE 1 > ALL((SELECT 1 FROM t1 RIGHT OUTER JOIN t1 a
ON (MATCH(t1.f1) AGAINST (""))
WHERE t1.f1 GROUP BY t1.f1))';
EXECUTE stmt;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 system NULL NULL NULL NULL 1
2 SUBQUERY a system NULL NULL NULL NULL 1 Using filesort
2 SUBQUERY t1 fulltext f1 f1 0 1 Using where
EXECUTE stmt;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 system NULL NULL NULL NULL 1
2 SUBQUERY a system NULL NULL NULL NULL 1 Using filesort
2 SUBQUERY t1 fulltext f1 f1 0 1 Using where
DEALLOCATE PREPARE stmt;
PREPARE stmt FROM
'EXPLAIN SELECT 1 FROM t1
WHERE 1 > ALL((SELECT 1 FROM t1 JOIN t1 a
ON (MATCH(t1.f1) AGAINST (""))
WHERE t1.f1 GROUP BY t1.f1))';
EXECUTE stmt;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 system NULL NULL NULL NULL 1
2 SUBQUERY a system NULL NULL NULL NULL 1 Using filesort
2 SUBQUERY t1 fulltext f1 f1 0 1 Using where
EXECUTE stmt;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 system NULL NULL NULL NULL 1
2 SUBQUERY a system NULL NULL NULL NULL 1 Using filesort
2 SUBQUERY t1 fulltext f1 f1 0 1 Using where
DEALLOCATE PREPARE stmt;
DROP TABLE t1;
End of 5.1 tests.

36
mysql-test/t/explain.test
View file

@ -228,4 +228,40 @@ EXPLAIN SELECT c1 FROM t1 WHERE c2 = 1 AND c4 = 1 AND c5 = 1;
DROP TABLE t1;
--echo #
--echo # Bug#56814 Explain + subselect + fulltext crashes server
--echo #
CREATE TABLE t1(f1 VARCHAR(6) NOT NULL,
FULLTEXT KEY(f1),UNIQUE(f1));
INSERT INTO t1 VALUES ('test');
EXPLAIN SELECT 1 FROM t1
WHERE 1 > ALL((SELECT 1 FROM t1 JOIN t1 a ON (MATCH(t1.f1) AGAINST (""))
WHERE t1.f1 GROUP BY t1.f1));
PREPARE stmt FROM
'EXPLAIN SELECT 1 FROM t1
WHERE 1 > ALL((SELECT 1 FROM t1 RIGHT OUTER JOIN t1 a
ON (MATCH(t1.f1) AGAINST (""))
WHERE t1.f1 GROUP BY t1.f1))';
EXECUTE stmt;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
PREPARE stmt FROM
'EXPLAIN SELECT 1 FROM t1
WHERE 1 > ALL((SELECT 1 FROM t1 JOIN t1 a
ON (MATCH(t1.f1) AGAINST (""))
WHERE t1.f1 GROUP BY t1.f1))';
EXECUTE stmt;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
DROP TABLE t1;
--echo End of 5.1 tests.

15
sql/item_subselect.cc
View file

@ -1906,21 +1906,26 @@ int subselect_single_select_engine::exec()
DBUG_RETURN(join->error ? join->error : 1);
}
if (!select_lex->uncacheable && thd->lex->describe &&
!(join->select_options & SELECT_DESCRIBE) &&
join->need_tmp)
!(join->select_options & SELECT_DESCRIBE))
{
item->update_used_tables();
if (item->const_item())
{
/*
It's necessary to keep original JOIN table because
create_sort_index() function may overwrite original
JOIN_TAB::type and wrong optimization method can be
selected on re-execution.
*/
select_lex->uncacheable|= UNCACHEABLE_EXPLAIN;
select_lex->master_unit()->uncacheable|= UNCACHEABLE_EXPLAIN;
/*
Force join->join_tmp creation, because this subquery will be replaced
by a simple select from the materialization temp table by optimize()
called by EXPLAIN and we need to preserve the initial query structure
so we can display it.
*/
select_lex->uncacheable|= UNCACHEABLE_EXPLAIN;
select_lex->master_unit()->uncacheable|= UNCACHEABLE_EXPLAIN;
if (join->init_save_join_tab())
if (join->need_tmp && join->init_save_join_tab())
DBUG_RETURN(1); /* purecov: inspected */
}
}

14
sql/sql_select.cc
View file

@ -2490,6 +2490,13 @@ mysql_select(THD *thd, Item ***rref_pointer_array,
{
DBUG_RETURN(TRUE);
}
/*
Original join tabs might be overwritten at first
subselect execution. So we need to restore them.
*/
Item_subselect *subselect= select_lex->master_unit()->item;
if (subselect && subselect->is_uncacheable() && join->reinit())
DBUG_RETURN(TRUE);
}
else
{
@ -8825,6 +8832,13 @@ simplify_joins(JOIN *join, List<TABLE_LIST> *join_list, COND *conds, bool top)
that reject nulls => the outer join can be replaced by an inner join.
*/
table->outer_join= 0;
/*
Update TABLE::maybe_null field as it could have
the value(maybe_null==TRUE) based on the assumption
that this join is outer(see setup_table_map() func).
*/
if (table->table)
table->table->maybe_null= FALSE;
if (table->on_expr)
{
/* Add on expression to the where condition. */