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	index_merge	a,b	b,a	5,5	NULL	1	Using intersect(b,a); Using where; Using index
select * from t1 where b = 255 AND a IS NULL;
pk	a	b
10000	NULL	255
drop table t1;