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# MDEV-36410 wrong result with index_merge on indexes having descending primary key
#
set optimizer_trace='enabled=on';
SET @save_sort_buffer_size=@@sort_buffer_size;
SET SESSION sort_buffer_size = 1024*16;
CREATE TABLE t1 (
id bigint(20) NOT NULL,
title varchar(255) NOT NULL,
status tinyint(4) DEFAULT 0,
country_code varchar(5) DEFAULT NULL,
PRIMARY KEY (id),
KEY idx_status (status),
KEY idx_country_code_status_id (country_code,status,id DESC)
) ENGINE=InnoDB;
INSERT INTO t1(id,title,status,country_code)
SELECT seq, CONCAT('abc', seq), seq%10, CONCAT('C', seq%5) FROM seq_1_to_500;
# This must not use index_merge:
EXPLAIN
SELECT * FROM t1 WHERE country_code ='C1' and `status` =1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref idx_status,idx_country_code_status_id idx_status 2 const 50 Using where
set @trace= (select JSON_EXTRACT(trace, '$**.range_scan_alternatives[*]')
from INFORMATION_SCHEMA.OPTIMIZER_TRACE);
select json_detailed(json_extract(@trace, '$[*].index')) as INDEXES;
INDEXES
[
"idx_status",
"idx_country_code_status_id"
]
select json_detailed(json_extract(@trace, '$[*].rowid_ordered')) as ROR;
ROR
[
true,
false
]
DROP table t1;
# Now, try with indexes using ASC ordering and PK using DESC
CREATE TABLE t1 (
id bigint(20) NOT NULL,
title varchar(255) NOT NULL,
status tinyint(4) DEFAULT 0,
country_code varchar(5) DEFAULT NULL,
PRIMARY KEY (id DESC),
KEY idx_status (status),
KEY idx_country_code_status_id (country_code,status,id)
) ENGINE=InnoDB;
INSERT INTO t1(id,title,status,country_code)
SELECT seq, CONCAT('abc', seq), seq%10, CONCAT('C', seq%5) FROM seq_1_to_500;
# Must not use index_merge:
EXPLAIN
SELECT * FROM t1 WHERE country_code ='C1' and status = 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref idx_status,idx_country_code_status_id idx_status 2 const 50 Using where
set @trace= (select JSON_EXTRACT(trace, '$**.range_scan_alternatives[*]')
from INFORMATION_SCHEMA.OPTIMIZER_TRACE);
select json_detailed(json_extract(@trace, '$[*].index')) as INDEXES;
INDEXES
[
"idx_status",
"idx_country_code_status_id"
]
select json_detailed(json_extract(@trace, '$[*].rowid_ordered')) as ROR;
ROR
[
true,
false
]
DROP TABLE t1;
# Now, try with indexes using DESC ordering and PK using DESC
CREATE TABLE t1 (
id bigint(20) NOT NULL,
title varchar(255) NOT NULL,
status tinyint(4) DEFAULT 0,
country_code varchar(5) DEFAULT NULL,
PRIMARY KEY (id DESC),
KEY idx_status (status),
KEY idx_country_code_status_id (country_code,status,id DESC)
) ENGINE=InnoDB;
INSERT INTO t1(id,title,status,country_code)
SELECT seq, CONCAT('abc', seq), seq%10, CONCAT('C', seq%5) FROM seq_1_to_500;
# Must not use index_merge:
EXPLAIN
SELECT * FROM t1 WHERE country_code ='C1' and status = 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref idx_status,idx_country_code_status_id idx_status 2 const 50 Using where
set @trace= (select JSON_EXTRACT(trace, '$**.range_scan_alternatives[*]')
from INFORMATION_SCHEMA.OPTIMIZER_TRACE);
select json_detailed(json_extract(@trace, '$[*].index')) as INDEXES;
INDEXES
[
"idx_status",
"idx_country_code_status_id"
]
select json_detailed(json_extract(@trace, '$[*].rowid_ordered')) as ROR;
ROR
[
true,
false
]
DROP TABLE t1;
SET sort_buffer_size= @save_sort_buffer_size;