Commit e093fb1f authored by evgen@moonbone.local's avatar evgen@moonbone.local

Fix bug#13293 Wrongly used index results in endless loop.

Loose index scan using only second part of multipart index was choosen, which
results in creating wrong keys and endless loop.

get_best_group_min_max() now allows loose index scan for distinct only if used
keyparts forms a prefix of the index.
parent 21a9d6a6
......@@ -2002,3 +2002,13 @@ a count(a)
1 1
NULL 1
drop table t1;
create table t1 (f1 int, f2 char(1), primary key(f1,f2)) engine=innodb;
insert into t1 values ( 1,"e"),(2,"a"),( 3,"c"),(4,"d");
alter table t1 drop primary key, add primary key (f2, f1);
explain select distinct f1 a, f1 b from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index NULL PRIMARY 5 NULL 4 Using index; Using temporary
explain select distinct f1, f2 from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL PRIMARY 5 NULL 3 Using index for group-by; Using temporary
drop table t1;
......@@ -693,3 +693,13 @@ create table t1(a int, key(a)) engine=innodb;
insert into t1 values(1);
select a, count(a) from t1 group by a with rollup;
drop table t1;
#
# Bug #13293 Wrongly used index results in endless loop.
#
create table t1 (f1 int, f2 char(1), primary key(f1,f2)) engine=innodb;
insert into t1 values ( 1,"e"),(2,"a"),( 3,"c"),(4,"d");
alter table t1 drop primary key, add primary key (f2, f1);
explain select distinct f1 a, f1 b from t1;
explain select distinct f1, f2 from t1;
drop table t1;
......@@ -7197,6 +7197,7 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
{
select_items_it.rewind();
cur_used_key_parts.clear_all();
uint max_key_part= 0;
while ((item= select_items_it++))
{
item_field= (Item_field*) item; /* (SA5) already checked above. */
......@@ -7214,7 +7215,19 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
cur_group_prefix_len+= cur_part->store_length;
cur_used_key_parts.set_bit(key_part_nr);
++cur_group_key_parts;
max_key_part= max(max_key_part,key_part_nr);
}
/*
Check that used key parts forms a prefix of the index.
To check this we compare bits in all_parts and cur_parts.
all_parts have all bits set from 0 to (max_key_part-1).
cur_parts have bits set for only used keyparts.
*/
ulonglong all_parts, cur_parts;
all_parts= (1<<max_key_part) - 1;
cur_parts= cur_used_key_parts.to_ulonglong() >> 1;
if (all_parts != cur_parts)
goto next_index;
}
else
DBUG_ASSERT(FALSE);
......
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