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Bug#38195: Incorrect handling of aggregate functions when loose index scan is

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used causes server crash.

When the loose index scan access method is used values of aggregated functions
are precomputed by it. Aggregation of such functions shouldn't be performed
in this case and functions should be treated as normal ones.
The create_tmp_table function wasn't taking this into account and this led to
a crash if a query has MIN/MAX aggregate functions and employs temporary table
and loose index scan.
Now the JOIN::exec and the create_tmp_table functions treat MIN/MAX aggregate
functions as normal ones when the loose index scan is used.


mysql-test/r/group_min_max.result:
  Added a test case for the bug#38195.
mysql-test/t/group_min_max.test:
  Added a test case for the bug#38195.
sql/sql_select.cc:
  Bug#38195: Incorrect handling of aggregate functions when loose index scan is
  used causes server crash.
  Now the JOIN::exec and the create_tmp_table functions treat MIN/MAX aggregate
  functions as normal ones when the loose index scan is used.
This commit is contained in:
Evgeny Potemkin 2008-08-13 22:24:55 +04:00
parent 8ed209b21d
commit b789b4f33c
3 changed files with 43 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

27
mysql-test/r/group_min_max.result
View file

@ -2353,3 +2353,30 @@ a MIN(b) MAX(b) AVG(b)
2 1 3 2.0000
1 1 3 2.0000
DROP TABLE t1;
create table t1 (a int, b int, primary key (a,b), key `index` (a,b)) engine=MyISAM;
insert into t1 (a,b) values (0,0),(0,1),(0,2),(0,3),(0,4),(0,5),(0,6),(0,7),
(0,8),(0,9),(0,10),(0,11),(0,12),(0,13);
insert into t1 (a,b) select a, max(b)+1 from t1 where a = 0 group by a;
select * from t1;
a b
0 0
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
0 10
0 11
0 12
0 13
0 14
explain extended select sql_buffer_result a, max(b)+1 from t1 where a = 0 group by a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range PRIMARY,index PRIMARY 4 NULL 6 Using where; Using index for group-by; Using temporary
Warnings:
Note 1003 select sql_buffer_result `test`.`t1`.`a` AS `a`,(max(`test`.`t1`.`b`) + 1) AS `max(b)+1` from `test`.`t1` where (`test`.`t1`.`a` = 0) group by `test`.`t1`.`a`
drop table t1;

12
mysql-test/t/group_min_max.test
View file

@ -916,3 +916,15 @@ SELECT a, MIN(b), MAX(b), AVG(b) FROM t1 GROUP BY a ORDER BY a DESC;
SELECT a, MIN(b), MAX(b), AVG(b) FROM t1 GROUP BY a ORDER BY a DESC;
DROP TABLE t1;
#
# Bug#38195: Incorrect handling of aggregate functions when loose index scan is
# used causes server crash.
#
create table t1 (a int, b int, primary key (a,b), key `index` (a,b)) engine=MyISAM;
insert into t1 (a,b) values (0,0),(0,1),(0,2),(0,3),(0,4),(0,5),(0,6),(0,7),
(0,8),(0,9),(0,10),(0,11),(0,12),(0,13);
insert into t1 (a,b) select a, max(b)+1 from t1 where a = 0 group by a;
select * from t1;
explain extended select sql_buffer_result a, max(b)+1 from t1 where a = 0 group by a;
drop table t1;

5
sql/sql_select.cc
View file

@ -1724,7 +1724,8 @@ JOIN::exec()
if (!items1)
{
items1= items0 + all_fields.elements;
if (sort_and_group || curr_tmp_table->group)
if (sort_and_group || curr_tmp_table->group ||
tmp_table_param.precomputed_group_by)
{
if (change_to_use_tmp_fields(thd, items1,
tmp_fields_list1, tmp_all_fields1,
@ -9259,6 +9260,8 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
MI_COLUMNDEF *recinfo;
uint total_uneven_bit_length= 0;
bool force_copy_fields= param->force_copy_fields;
/* Treat sum functions as normal ones when loose index scan is used. */
save_sum_fields|= param->precomputed_group_by;
DBUG_ENTER("create_tmp_table");
DBUG_PRINT("enter",("distinct: %d save_sum_fields: %d rows_limit: %lu group: %d",
(int) distinct, (int) save_sum_fields,