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Fix for BUG#11044 - "SELECT DISTINCT on indexed column returns inconsistent results"

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The problem was that when there was no MIN or MAX function, after finding the
group prefix based on the DISTINCT or GROUP BY attributes we did not search further
for a key in the group that satisfies the equi-join conditions on attributes that
follow the group attributes. Thus we ended up with the wrong rows, and subsequent
calls to select_cond->val_int() in evaluate_join_record() were filtering those
rows. Hence - the query result set was empty.

The problem occured both for GROUP BY queries without MIN/MAX and for queries
with DISTINCT (which were internally executed as GROUP BY queries).
This commit is contained in:
timour@mysql.com
2005-06-14 12:52:44 +03:00
parent 95e620485c
commit 37a84e5250
3 changed files with 44 additions and 9 deletions
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18
mysql-test/r/group_min_max.result
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@@ -1954,6 +1954,24 @@ id select_type table type possible_keys key key_len ref rows Extra
explain select sum(ord(a1)) from t1 where (a1 > 'a') group by a1,a2,b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index idx_t1_0,idx_t1_1,idx_t1_2 idx_t1_1 163 NULL 128 Using where; Using index
explain select a1 from t1 where a2 = 'b' group by a1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL idx_t1_1 130 NULL 5 Using where; Using index for group-by
select a1 from t1 where a2 = 'b' group by a1;
a1
a
b
c
d
explain select distinct a1 from t1 where a2 = 'b';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL idx_t1_1 130 NULL 5 Using where; Using index for group-by
select distinct a1 from t1 where a2 = 'b';
a1
a
b
c
d
drop table t1;
drop table t2;
drop table t3;