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Bug #39653: find_shortest_key in sql_select.cc does not

consider clustered primary keys

Choosing a shortest index for the covering index scan,
the optimizer ignored the fact, that the clustered primary
key read involves whole table data.

The find_shortest_key function has been modified to
take into account that fact that a clustered PK has a
longest key of possible covering indices.


mysql-test/r/innodb_mysql.result:
  Test case for bug #39653.
mysql-test/t/innodb_mysql.test:
  Test case for bug #39653.
sql/sql_select.cc:
  Bug #39653: find_shortest_key in sql_select.cc does not
              consider clustered primary keys
  
  The find_shortest_key function has been modified to
  take into account that fact that a clustered PK has a
  longest key of possible covering indices.
This commit is contained in:
Gleb Shchepa
2010-03-05 23:45:55 +04:00
parent fbad82deaa
commit 63a88e1373
3 changed files with 65 additions and 2 deletions

View File

@ -2295,4 +2295,26 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ref f1 f1 4 test.t1.f1 1 Using index
drop table t1,t2;
#
#
# Bug #39653: find_shortest_key in sql_select.cc does not consider
# clustered primary keys
#
CREATE TABLE t1 (a INT PRIMARY KEY, b INT, c INT, d INT, e INT, f INT,
KEY (b,c)) ENGINE=INNODB;
INSERT INTO t1 VALUES (1,1,1,1,1,1), (2,2,2,2,2,2), (3,3,3,3,3,3),
(4,4,4,4,4,4), (5,5,5,5,5,5), (6,6,6,6,6,6),
(7,7,7,7,7,7), (8,8,8,8,8,8), (9,9,9,9,9,9),
(11,11,11,11,11,11);
EXPLAIN SELECT COUNT(*) FROM t1;
id 1
select_type SIMPLE
table t1
type index
possible_keys NULL
key b
key_len 10
ref NULL
rows 10
Extra Using index
DROP TABLE t1;
End of 5.1 tests