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create table t1 (
a int,
key (a desc)
);
insert into t1 select seq from seq_1_to_1000;
set optimizer_trace=1;
explain select * from t1 force index(a) where a in (2, 4, 6);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range a a 5 NULL 3 Using where; Using index
select json_detailed(json_extract(trace, '$**.range_access_plan.ranges')) as jd
from information_schema.optimizer_trace;
jd
[
[
"(6) <= (a DESC) <= (6)",
"(4) <= (a DESC) <= (4)",
"(2) <= (a DESC) <= (2)"
]
]
set optimizer_trace=default;
# These should go in reverse order:
select * from t1 force index(a) where a in (2, 4, 6);
a
6
4
2
drop table t1;
#
# Multi-part key tests
#
create table t1 (
a int not null,
b int not null,
key ab(a, b desc)
);
insert into t1 select A.seq, B.seq*10 from seq_1_to_10 A, seq_1_to_10 B;
set optimizer_trace=1;
explain select * from t1 force index(ab) where a>=8 and b>=50;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range ab ab 4 NULL 51 Using where; Using index
select json_detailed(json_extract(trace, '$**.range_access_plan.ranges')) as jd
from information_schema.optimizer_trace;
jd
[
["(8) <= (a)"]
]
explain select * from t1 force index(ab) where a>=8 and b<=50;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range ab ab 8 NULL 46 Using where; Using index
select json_detailed(json_extract(trace, '$**.range_access_plan.ranges')) as jd
from information_schema.optimizer_trace;
jd
[
["(8,50) <= (a,b DESC)"]
]
select * from t1 force index(ab) where a>=8 and b<=50;
a b
8 50
8 40
8 30
8 20
8 10
9 50
9 40
9 30
9 20
9 10
10 50
10 40
10 30
10 20
10 10
select * from t1 ignore index(ab) where a>=8 and b<=50 order by a, b desc;
a b
8 50
8 40
8 30
8 20
8 10
9 50
9 40
9 30
9 20
9 10
10 50
10 40
10 30
10 20
10 10
explain
select * from t1 where a between 2 and 4 and b between 50 and 80;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range ab ab 8 NULL 17 Using where; Using index
select json_detailed(json_extract(trace, '$**.range_access_plan.ranges')) as jd
from information_schema.optimizer_trace;
jd
[
["(2,80) <= (a,b DESC) <= (4,50)"]
]
select * from t1 where a between 2 and 4 and b between 50 and 80;
a b
2 80
2 70
2 60
2 50
3 80
3 70
3 60
3 50
4 80
4 70
4 60
4 50
drop table t1;
create table t2 (
a int not null,
b int not null,
key ab(a desc, b desc)
);
insert into t2 select A.seq, B.seq*10 from seq_1_to_10 A, seq_1_to_10 B;
explain
select * from t2 where a between 2 and 4;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 range ab ab 4 NULL 40 Using where; Using index
select json_detailed(json_extract(trace, '$**.range_access_plan.ranges')) as jd
from information_schema.optimizer_trace;
jd
[
["(4) <= (a DESC) <= (2)"]
]
explain
select * from t2 where a between 2 and 4 and b between 50 and 80;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 range ab ab 8 NULL 31 Using where; Using index
select json_detailed(json_extract(trace, '$**.range_access_plan.ranges')) as jd
from information_schema.optimizer_trace;
jd
[
["(4,80) <= (a DESC,b DESC) <= (2,50)"]
]
drop table t2;
#
# Check that "Using index for group-by" is disabled (it's not supported, yet)
#
CREATE TABLE t1 (p int NOT NULL, a int NOT NULL, PRIMARY KEY (p,a desc));
insert into t1 select 2,seq from seq_0_to_1000;
EXPLAIN select MIN(a) from t1 where p = 2 group by p;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref PRIMARY PRIMARY 4 const 1000 Using index
select json_detailed(json_extract(trace, '$**.potential_group_range_indexes')) as jd
from information_schema.optimizer_trace;
jd
[
[
{
"index": "PRIMARY",
"usable": false,
"cause": "Reverse-ordered (not supported yet)"
}
]
]
drop table t1;
set optimizer_trace=default;
#
# MDEV-27426: Wrong result upon query using index_merge with DESC key
#
CREATE TABLE t1 (pk INT, a INT, b int, KEY(a), PRIMARY KEY(pk DESC))
ENGINE=InnoDB;
INSERT INTO t1 VALUES (1,4,5),(2,9,6),(3,NULL,7),(4,NULL,8);
SELECT * FROM t1 WHERE pk > 10 OR a > 0;
pk a b
2 9 6
1 4 5
DROP TABLE t1;
#
# MDEV-27529: Wrong result upon query using index_merge with DESC key (#2)
#
create table t1 (
pk int,
a int,
b int,
primary key(pk desc),
key(a),
key(b)
) engine=innodb;
insert into t1 values (0, 111111, 255);
insert into t1 select seq+50000, NULL, seq+1000 from seq_1_to_260;
insert into t1 values (10000, NULL, 255);
insert into t1 select seq+20000, seq+20000, seq+20000 from seq_1_to_1500;
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
# Must use ROR-intersect:
explain select * from t1 where b = 255 AND a IS NULL;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref a,b b 5 const 2 Using where
select * from t1 where b = 255 AND a IS NULL;
pk a b
10000 NULL 255
drop table t1;
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