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DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (b BLOB <CUSTOM_COL_OPTIONS>,
t TINYBLOB <CUSTOM_COL_OPTIONS>,
m MEDIUMBLOB <CUSTOM_COL_OPTIONS>,
l LONGBLOB <CUSTOM_COL_OPTIONS>,
<CUSTOM_INDEX> b (b(32))
) ENGINE=<STORAGE_ENGINE> <CUSTOM_TABLE_OPTIONS>;
SHOW INDEX IN t1;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
t1 1 # 1 b # # 32 NULL # #
INSERT INTO t1 (b,t,m,l) VALUES
('','','',''),
('a','b','c','d'),
('b','d','c','b'),
('test1','test2','test3','test4'),
(REPEAT('a',128),REPEAT('b',128),REPEAT('c',128),REPEAT('d',128)),
(HEX('abcd'),HEX('def'),HEX('a'),HEX('abc')),
('abc','def','ghi','jkl'),
('test2','test3','test4','test5'),
('test3','test4','test5','test6'),
(REPEAT('b',128),REPEAT('f',128),REPEAT('e',128),REPEAT('d',128)),
(REPEAT('c',128),REPEAT('b',128),REPEAT('c',128),REPEAT('e',128));
SELECT SUBSTRING(b,16) AS f FROM t1 WHERE b IN ('test1','test2') ORDER BY f;
f
SELECT SUBSTRING(b,16) AS f FROM t1 USE INDEX () WHERE b IN ('test1','test2') ORDER BY f;
f
DROP TABLE t1;
CREATE TABLE t1 (b BLOB <CUSTOM_COL_OPTIONS>,
t TINYBLOB <CUSTOM_COL_OPTIONS>,
m MEDIUMBLOB <CUSTOM_COL_OPTIONS>,
l LONGBLOB <CUSTOM_COL_OPTIONS>,
PRIMARY KEY b (b(32))
) ENGINE=<STORAGE_ENGINE> <CUSTOM_TABLE_OPTIONS>;
SHOW INDEX IN t1;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
t1 0 PRIMARY 1 b # # 32 NULL # #
INSERT INTO t1 (b,t,m,l) VALUES
('','','',''),
('a','b','c','d'),
('b','d','c','b'),
('test1','test2','test3','test4'),
(REPEAT('a',128),REPEAT('b',128),REPEAT('c',128),REPEAT('d',128)),
(HEX('abcd'),HEX('def'),HEX('a'),HEX('abc')),
('abc','def','ghi','jkl'),
('test2','test3','test4','test5'),
('test3','test4','test5','test6'),
(REPEAT('b',128),REPEAT('f',128),REPEAT('e',128),REPEAT('d',128)),
(REPEAT('c',128),REPEAT('b',128),REPEAT('c',128),REPEAT('e',128));
EXPLAIN SELECT SUBSTRING(b,16) AS f FROM t1 WHERE b IN ('test1','test2') ORDER BY f;
id select_type table type possible_keys key key_len ref rows Extra
# # # # # PRIMARY # # # #
SELECT SUBSTRING(b,16) AS f FROM t1 WHERE b IN ('test1','test2') ORDER BY f;
f
EXPLAIN SELECT SUBSTRING(b,16) AS f FROM t1 USE INDEX () WHERE b IN ('test1','test2') ORDER BY f;
id select_type table type possible_keys key key_len ref rows Extra
# # # # # NULL # # # #
SELECT SUBSTRING(b,16) AS f FROM t1 USE INDEX () WHERE b IN ('test1','test2') ORDER BY f;
f
DROP TABLE t1;
CREATE TABLE t1 (b BLOB <CUSTOM_COL_OPTIONS>,
t TINYBLOB <CUSTOM_COL_OPTIONS>,
m MEDIUMBLOB <CUSTOM_COL_OPTIONS>,
l LONGBLOB <CUSTOM_COL_OPTIONS>,
UNIQUE INDEX l_t (l(256),t(64))
) ENGINE=<STORAGE_ENGINE> <CUSTOM_TABLE_OPTIONS>;
SHOW INDEX IN t1;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
t1 0 l_t 1 l # # 256 NULL # #
t1 0 l_t 2 t # # 64 NULL # #
INSERT INTO t1 (b,t,m,l) VALUES
('','','',''),
('a','b','c','d'),
('b','d','c','b'),
('test1','test2','test3','test4'),
(REPEAT('a',128),REPEAT('b',128),REPEAT('c',128),REPEAT('d',128)),
(HEX('abcd'),HEX('def'),HEX('a'),HEX('abc')),
('abc','def','ghi','jkl'),
('test2','test3','test4','test5'),
('test3','test4','test5','test6'),
(REPEAT('b',128),REPEAT('f',128),REPEAT('e',128),REPEAT('d',128)),
(REPEAT('c',128),REPEAT('b',128),REPEAT('c',128),REPEAT('e',128));
EXPLAIN SELECT SUBSTRING(t,64), SUBSTRING(l,256) FROM t1 WHERE t!=l AND l NOT IN ('test1') ORDER BY t, l DESC;
id select_type table type possible_keys key key_len ref rows Extra
# # # # l_t # # # # #
SELECT SUBSTRING(t,64), SUBSTRING(l,256) FROM t1 WHERE t!=l AND l NOT IN ('test1') ORDER BY t, l DESC;
SUBSTRING(t,64) SUBSTRING(l,256)
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
EXPLAIN SELECT SUBSTRING(t,64), SUBSTRING(l,256) FROM t1 FORCE INDEX (l_t) WHERE t!=l AND l NOT IN ('test1') ORDER BY t, l DESC;
id select_type table type possible_keys key key_len ref rows Extra
# # # # l_t # # # # #
SELECT SUBSTRING(t,64), SUBSTRING(l,256) FROM t1 FORCE INDEX (l_t) WHERE t!=l AND l NOT IN ('test1') ORDER BY t, l DESC;
SUBSTRING(t,64) SUBSTRING(l,256)
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
DROP TABLE t1;
CREATE TABLE t1 (b BLOB <CUSTOM_COL_OPTIONS>,
t TINYBLOB <CUSTOM_COL_OPTIONS>,
m MEDIUMBLOB <CUSTOM_COL_OPTIONS>,
l LONGBLOB <CUSTOM_COL_OPTIONS>,
INDEX (m(128))
) ENGINE=<STORAGE_ENGINE> <CUSTOM_TABLE_OPTIONS>;
SHOW INDEX IN t1;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
t1 1 m 1 m # # 128 NULL # #
INSERT INTO t1 (b,t,m,l) VALUES
('','','',''),
('a','b','c','d'),
('b','d','c','b'),
('test1','test2','test3','test4'),
(REPEAT('a',128),REPEAT('b',128),REPEAT('c',128),REPEAT('d',128)),
(HEX('abcd'),HEX('def'),HEX('a'),HEX('abc')),
('abc','def','ghi','jkl'),
('test2','test3','test4','test5'),
('test3','test4','test5','test6'),
(REPEAT('b',128),REPEAT('f',128),REPEAT('e',128),REPEAT('d',128)),
(REPEAT('c',128),REPEAT('b',128),REPEAT('c',128),REPEAT('e',128));
EXPLAIN SELECT SUBSTRING(m,128) AS f FROM t1 WHERE m = 'test1' ORDER BY f DESC;
id select_type table type possible_keys key key_len ref rows Extra
# # # # # m # # # #
SELECT SUBSTRING(m,128) AS f FROM t1 WHERE m = 'test1' ORDER BY f DESC;
f
EXPLAIN SELECT SUBSTRING(m,128) AS f FROM t1 IGNORE INDEX FOR ORDER BY (m) WHERE m = 'test1' ORDER BY f DESC;
id select_type table type possible_keys key key_len ref rows Extra
# # # # # m # # # #
SELECT SUBSTRING(m,128) AS f FROM t1 IGNORE INDEX FOR ORDER BY (m) WHERE m = 'test1' ORDER BY f DESC;
f
DROP TABLE t1;
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