MDEV-26294 Duplicate entries in unique index not detected when changing collation

Problem: ======= ALTER TABLE in InnoDB fails to detect duplicate entries for the unique index when the character set or collation of an indexed column is changed in such a way that the character encoding is compatible with the old table definition. In this case, any secondary indexes on the changed columns would be rebuilt (DROP INDEX, ADD INDEX). Solution: ======== During ALTER TABLE, InnoDB keeps track of columns whose collation changed, and will fill in the correct metadata when sorting the index records, or applying changes from concurrent DML. This metadata will be allocated in the dict_index_t::heap of the being-created secondary indexes. The fix was developed by Thirunarayanan Balathandayuthapani and simplified by me.

MDEV-26294 Duplicate entries in unique index not detected when changing collation
Problem: ======= ALTER TABLE in InnoDB fails to detect duplicate entries for the unique index when the character set or collation of an indexed column is changed in such a way that the character encoding is compatible with the old table definition. In this case, any secondary indexes on the changed columns would be rebuilt (DROP INDEX, ADD INDEX). Solution: ======== During ALTER TABLE, InnoDB keeps track of columns whose collation changed, and will fill in the correct metadata when sorting the index records, or applying changes from concurrent DML. This metadata will be allocated in the dict_index_t::heap of the being-created secondary indexes. The fix was developed by Thirunarayanan Balathandayuthapani and simplified by me.
f8240a27 · Marko Mäkelä · f43145a0 · f8240a27 · f8240a27 · f8240a27
Commit f8240a27 authored Jul 04, 2022 by Marko Mäkelä
13 changed files
--- a/mysql-test/suite/innodb/r/change_column_collation.result
+++ b/mysql-test/suite/innodb/r/change_column_collation.result
@@ -9,11 +9,89 @@ msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_swedish_ci UNIQUE
 ) ENGINE=INNODB;
 INSERT INTO t1 VALUES (1, 'aaa');
 INSERT INTO t1 VALUES (2, 'ååå');
-ALTER TABLE t1
+ALTER TABLE t1 MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci, ALGORITHM=inplace;
-MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci,
+ERROR 23000: Duplicate entry 'NULL' for key 'msg'
-ALGORITHM=NOCOPY;
+DROP TABLE t1;
-ERROR 0A000: ALGORITHM=NOCOPY is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+CREATE TABLE t1 (
-ALTER TABLE t1 DROP INDEX msg,
+id INT PRIMARY KEY,
-MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci,
+msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_bin,
-ALGORITHM=NOCOPY;
+id_2 INT not null,
+unique index(msg, id_2)
+) ENGINE=INNODB;
+INSERT INTO t1 VALUES (1, 'aaa', 2);
+INSERT INTO t1 VALUES (2, 'AAA', 3);
+ALTER TABLE t1 MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci, ALGORITHM=inplace;
+DROP TABLE t1;
+CREATE TABLE t1 (
+id INT PRIMARY KEY,
+msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_bin,
+unique index(msg)
+) ENGINE=INNODB;
+INSERT INTO t1 VALUES (1, 'aaa');
+INSERT INTO t1 VALUES (2, 'bbb');
+INSERT INTO t1 VALUES (3, 'ccc');
+SET DEBUG_SYNC = 'RESET';
+SET DEBUG_SYNC = 'row_log_apply_before SIGNAL before_apply WAIT_FOR go_ahead';
+ALTER TABLE t1 MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci, ALGORITHM=NOCOPY;
+connect  con1,localhost,root,,;
+connection con1;
+SET DEBUG_SYNC = 'now WAIT_FOR before_apply';
+INSERT INTO t1 VALUES (4, 'AAA');
+UPDATE t1 set msg = "ddd" where id = 2;
+DELETE FROM t1 WHERE id= 3;
+SET DEBUG_SYNC = 'now SIGNAL go_ahead';
+SET DEBUG_SYNC = 'RESET';
+connection default;
+ERROR 23000: Duplicate entry 'NULL' for key 'msg'
+SELECT * FROM t1;
+id	msg
+4	AAA
+1	aaa
+2	ddd
+DROP TABLE t1;
+CREATE TABLE t1 (
+id INT PRIMARY KEY,
+msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_bin,
+unique index(msg)
+) ENGINE=INNODB;
+INSERT INTO t1 VALUES (1, 'aaa');
+SET DEBUG_DBUG="+d,create_index_fail";
+SET DEBUG_SYNC="innodb_inplace_alter_table_enter SIGNAL con1_go WAIT_FOR alter_signal";
+ALTER TABLE t1 MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci, ALGORITHM=NOCOPY;
+connection con1;
+SET DEBUG_SYNC="now WAIT_FOR con1_go";
+BEGIN;
+SELECT * FROM t1;
+id	msg
+1	aaa
+SET DEBUG_SYNC="now SIGNAL alter_signal";
+connection default;
+ERROR 23000: Duplicate entry '' for key '*UNKNOWN*'
+connection con1;
+rollback;
+INSERT INTO t1 VALUES(2, 'bbb');
+disconnect con1;
+connection default;
+SET DEBUG_SYNC=reset;
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `id` int(11) NOT NULL,
+  `msg` varchar(100) CHARACTER SET utf8mb3 COLLATE utf8mb3_bin DEFAULT NULL,
+  PRIMARY KEY (`id`),
+  UNIQUE KEY `msg` (`msg`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+INSERT INTO t1 VALUES(3, 'ccc');
+DROP TABLE t1;
+CREATE TABLE t1(id INT PRIMARY KEY, msg VARCHAR(100),
+msg_1 VARCHAR(100) AS (msg) VIRTUAL,
+msg_2 VARCHAR(100) AS (msg) STORED,
+UNIQUE(msg), UNIQUE(msg_1),
+UNIQUE(msg_2))ENGINE=InnoDB;
+ALTER TABLE t1 MODIFY msg_1 VARCHAR(100) CHARACTER SET utf8
+COLLATE utf8_unicode_ci, ALGORITHM=inplace;
+ERROR HY000: This is not yet supported for generated columns
+ALTER TABLE t1 MODIFY msg_2 VARCHAR(100) CHARACTER SET utf8
+COLLATE utf8_unicode_ci, ALGORITHM=inplace;
+ERROR 0A000: ALGORITHM=INPLACE is not supported. Reason: Cannot change column type. Try ALGORITHM=COPY
 DROP TABLE t1;
--- a/mysql-test/suite/innodb/r/instant_alter_charset,redundant.rdiff
+++ b/mysql-test/suite/innodb/r/instant_alter_charset,redundant.rdiff
-@@ -288,7 +288,6 @@
+@@ -279,7 +279,6 @@
 alter table boundary_255
 modify a varchar(70) charset utf8mb4,
 algorithm=instant;
@@ -6,7 +6,7 @@
 drop table boundary_255;
 create table t (
 a char(10) collate utf8mb3_general_ci,
-@@ -306,35 +305,21 @@
+@@ -297,32 +296,21 @@
 repeat('a', 10), repeat('a', 10)
 );
 alter table t modify a char(10) collate utf8mb4_general_ci, algorithm=instant;
@@ -25,19 +25,16 @@
 -test.t	check	status	OK
 +ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Cannot change column type. Try ALGORITHM=COPY
 alter table t modify aa char(10) collate utf8mb4_general_ci, algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
 -check table t;
 -Table	Op	Msg_type	Msg_text
 -test.t	check	status	OK
 +ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Cannot change column type. Try ALGORITHM=COPY
 alter table t modify bb char(70) collate utf8mb4_general_ci, algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
 -check table t;
 -Table	Op	Msg_type	Msg_text
 -test.t	check	status	OK
 +ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Cannot change column type. Try ALGORITHM=COPY
 alter table t modify cc char(100) collate utf8mb4_general_ci, algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
 -check table t;
 -Table	Op	Msg_type	Msg_text
 -test.t	check	status	OK
@@ -45,10 +42,17 @@
 alter table t modify d char(10) collate utf8mb4_spanish_ci, algorithm=instant;
 +ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Cannot change column type. Try ALGORITHM=COPY
 alter table t modify dd char(10) collate utf8mb4_spanish_ci, algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 +ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Cannot change column type. Try ALGORITHM=COPY
 select * from t;
 a	b	c	aa	bb	cc	d	dd
 aaaaaaaaaa	aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa	aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa	aaaaaaaaaa	aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa	aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa	aaaaaaaaaa	aaaaaaaaaa
+@@ -2066,7 +2054,7 @@
-mysqltest: Result length mismatch
+ ALTER TABLE t1
+ CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci,
+ ADD UNIQUE INDEX test_key (a);
+-ERROR 23000: Duplicate entry 'NULL' for key 'test_key'
+ERROR 23000: Duplicate entry 'a1' for key 'test_key'
+ ALTER TABLE t1 CONVERT TO CHARACTER SET UTF8MB4 COLLATE UTF8MB4_UNICODE_520_CI;
+ CHECK TABLE t1;
+ Table	Op	Msg_type	Msg_text
--- a/mysql-test/suite/innodb/r/instant_alter_charset.result
+++ b/mysql-test/suite/innodb/r/instant_alter_charset.result
@@ -199,15 +199,6 @@ a varchar(150) charset utf8mb3 unique key
 alter table key_part_bug
 modify a varchar(150) charset utf8mb4,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table key_part_bug
-modify a varchar(150) charset utf8mb4,
-algorithm=nocopy;
-ERROR 0A000: ALGORITHM=NOCOPY is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table key_part_bug
-drop index a,
-modify a varchar(150) charset utf8mb4,
-algorithm=nocopy;
 drop table key_part_bug;
 create table latin1_swedish_special_case (
 copy1 varchar(150) charset ascii collate ascii_general_ci,
@@ -318,23 +309,20 @@ check table t;
 Table	Op	Msg_type	Msg_text
 test.t	check	status	OK
 alter table t modify aa char(10) collate utf8mb4_general_ci, algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
 check table t;
 Table	Op	Msg_type	Msg_text
 test.t	check	status	OK
 alter table t modify bb char(70) collate utf8mb4_general_ci, algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
 check table t;
 Table	Op	Msg_type	Msg_text
 test.t	check	status	OK
 alter table t modify cc char(100) collate utf8mb4_general_ci, algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
 check table t;
 Table	Op	Msg_type	Msg_text
 test.t	check	status	OK
 alter table t modify d char(10) collate utf8mb4_spanish_ci, algorithm=instant;
 alter table t modify dd char(10) collate utf8mb4_spanish_ci, algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 select * from t;
 a	b	c	aa	bb	cc	d	dd
 aaaaaaaaaa	aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa	aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa	aaaaaaaaaa	aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa	aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa	aaaaaaaaaa	aaaaaaaaaa
@@ -390,10 +378,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_general_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_general_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_general_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -407,10 +391,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_bin,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_bin,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_bin,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -424,10 +404,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_unicode_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_unicode_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_unicode_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -441,10 +417,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_icelandic_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_icelandic_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_icelandic_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -458,10 +430,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_latvian_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_latvian_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_latvian_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -475,10 +443,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_romanian_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_romanian_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_romanian_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -492,10 +456,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_slovenian_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_slovenian_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_slovenian_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -509,10 +469,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_polish_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_polish_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_polish_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -526,10 +482,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_estonian_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_estonian_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_estonian_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -543,10 +495,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_spanish_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_spanish_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_spanish_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -560,10 +508,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_swedish_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_swedish_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_swedish_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -577,10 +521,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_turkish_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_turkish_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_turkish_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -594,10 +534,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_czech_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_czech_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_czech_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -611,10 +547,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_danish_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_danish_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_danish_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -628,10 +560,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_lithuanian_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_lithuanian_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_lithuanian_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -645,10 +573,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_slovak_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_slovak_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_slovak_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -662,10 +586,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_spanish2_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_spanish2_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_spanish2_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -679,10 +599,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_roman_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_roman_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_roman_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -696,10 +612,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_persian_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_persian_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_persian_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -713,10 +625,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_esperanto_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_esperanto_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_esperanto_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -730,10 +638,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_hungarian_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_hungarian_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_hungarian_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -747,10 +651,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_sinhala_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_sinhala_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_sinhala_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -764,10 +664,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_german2_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_german2_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_german2_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -781,10 +677,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_croatian_mysql561_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_croatian_mysql561_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_croatian_mysql561_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -798,10 +690,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_unicode_520_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_unicode_520_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_unicode_520_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -815,10 +703,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_vietnamese_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_vietnamese_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_vietnamese_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -832,10 +716,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_croatian_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_croatian_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_croatian_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -849,10 +729,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_myanmar_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_myanmar_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_myanmar_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -866,10 +742,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_thai_520_w2,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_thai_520_w2,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_thai_520_w2,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -883,10 +755,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_general_nopad_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_general_nopad_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_general_nopad_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -900,10 +768,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_nopad_bin,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_nopad_bin,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_nopad_bin,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -917,10 +781,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_unicode_nopad_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_unicode_nopad_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_unicode_nopad_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -934,10 +794,6 @@ alter table tmp
 change a a varchar(50) charset utf8mb4 collate utf8mb4_unicode_520_nopad_ci,
 modify b varchar(50) charset utf8mb4 collate utf8mb4_unicode_520_nopad_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table tmp
-change a a varchar(50) charset utf8mb4 collate utf8mb4_unicode_520_nopad_ci,
-algorithm=instant;
 check table tmp;
 Table	Op	Msg_type	Msg_text
 test.tmp	check	status	OK
@@ -974,7 +830,7 @@ algorithm=instant;
 alter table tmp
 modify b varchar(50) charset utf8mb4 collate utf8mb4_vietnamese_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table tmp
 modify c varchar(50) charset utf8mb4 collate utf8mb4_vietnamese_ci,
 algorithm=instant;
@@ -991,7 +847,7 @@ algorithm=instant;
 alter table tmp
 modify b varchar(50) charset utf8mb4 collate utf8mb4_vietnamese_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table tmp
 modify c varchar(50) charset utf8mb4 collate utf8mb4_vietnamese_ci,
 algorithm=instant;
@@ -1008,7 +864,7 @@ algorithm=instant;
 alter table tmp
 modify b varchar(50) charset utf8mb4 collate utf8mb4_vietnamese_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table tmp
 modify c varchar(50) charset utf8mb4 collate utf8mb4_vietnamese_ci,
 algorithm=instant;
@@ -1025,7 +881,7 @@ algorithm=instant;
 alter table tmp
 modify b varchar(50) charset utf8mb4 collate utf8mb4_vietnamese_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table tmp
 modify c varchar(50) charset utf8mb4 collate utf8mb4_vietnamese_ci,
 algorithm=instant;
@@ -1042,7 +898,7 @@ algorithm=instant;
 alter table tmp
 modify b varchar(50) charset ascii collate ascii_bin,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table tmp
 modify c varchar(50) charset ascii collate ascii_bin,
 algorithm=instant;
@@ -1059,7 +915,7 @@ algorithm=instant;
 alter table tmp
 modify b varchar(50) charset utf8mb3 collate utf8mb3_lithuanian_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table tmp
 modify c varchar(50) charset utf8mb3 collate utf8mb3_lithuanian_ci,
 algorithm=instant;
@@ -1076,7 +932,7 @@ algorithm=instant;
 alter table tmp
 modify b varchar(50) charset utf8mb4 collate utf8mb4_persian_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table tmp
 modify c varchar(50) charset utf8mb4 collate utf8mb4_persian_ci,
 algorithm=instant;
@@ -1093,7 +949,7 @@ algorithm=instant;
 alter table tmp
 modify b varchar(50) charset utf8mb4 collate utf8mb4_german2_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table tmp
 modify c varchar(50) charset utf8mb4 collate utf8mb4_german2_ci,
 algorithm=instant;
@@ -1110,7 +966,7 @@ algorithm=instant;
 alter table tmp
 modify b varchar(50) charset utf8mb3 collate utf8mb3_unicode_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table tmp
 modify c varchar(50) charset utf8mb3 collate utf8mb3_unicode_ci,
 algorithm=instant;
@@ -1127,7 +983,7 @@ algorithm=instant;
 alter table tmp
 modify b varchar(50) charset latin1 collate latin1_general_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table tmp
 modify c varchar(50) charset latin1 collate latin1_general_ci,
 algorithm=instant;
@@ -1144,7 +1000,7 @@ algorithm=instant;
 alter table tmp
 modify b varchar(50) charset utf16 collate utf16_german2_ci,
 algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table tmp
 modify c varchar(50) charset utf16 collate utf16_german2_ci,
 algorithm=instant;
@@ -2031,11 +1887,8 @@ insert into t values
 alter table t modify a char(10) collate latin1_general_cs, algorithm=inplace;
 ERROR 0A000: ALGORITHM=INPLACE is not supported. Reason: Cannot change column type. Try ALGORITHM=COPY
 alter table t modify b char(10) collate latin1_general_cs, algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table t modify b char(10) collate latin1_general_cs, algorithm=nocopy;
-ERROR 0A000: ALGORITHM=NOCOPY is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table t modify b char(10) collate latin1_general_cs,
-drop index b_key, algorithm=nocopy;
 check table t;
 Table	Op	Msg_type	Msg_text
 test.t	check	status	OK
@@ -2055,11 +1908,8 @@ insert into t values
 alter table t modify a varchar(10) collate latin1_general_cs, algorithm=inplace;
 ERROR 0A000: ALGORITHM=INPLACE is not supported. Reason: Cannot change column type. Try ALGORITHM=COPY
 alter table t modify b varchar(10) collate latin1_general_cs, algorithm=instant;
-ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=INSTANT is not supported. Reason: ADD INDEX. Try ALGORITHM=NOCOPY
 alter table t modify b varchar(10) collate latin1_general_cs, algorithm=nocopy;
-ERROR 0A000: ALGORITHM=NOCOPY is not supported. Reason: Collation change on an indexed column. Try ALGORITHM=COPY
-alter table t modify b varchar(10) collate latin1_general_cs,
-drop index b_key, algorithm=nocopy;
 check table t;
 Table	Op	Msg_type	Msg_text
 test.t	check	status	OK
@@ -2201,7 +2051,7 @@ INSERT INTO t1 VALUES (1, 'a1'), (2, 'a1');
 ALTER TABLE t1
 CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci,
 ADD UNIQUE INDEX test_key (a);
-ERROR 23000: Duplicate entry 'a1' for key 'test_key'
+ERROR 23000: Duplicate entry 'NULL' for key 'test_key'
 ALTER TABLE t1 CONVERT TO CHARACTER SET UTF8MB4 COLLATE UTF8MB4_UNICODE_520_CI;
 CHECK TABLE t1;
 Table	Op	Msg_type	Msg_text
@@ -2216,7 +2066,7 @@ INSERT INTO t1 VALUES (1, 'a1'), (2, 'a1');
 ALTER TABLE t1
 CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci,
 ADD UNIQUE INDEX test_key (a);
-ERROR 23000: Duplicate entry 'a1' for key 'test_key'
+ERROR 23000: Duplicate entry 'NULL' for key 'test_key'
 ALTER TABLE t1 CONVERT TO CHARACTER SET UTF8MB4 COLLATE UTF8MB4_UNICODE_520_CI;
 CHECK TABLE t1;
 Table	Op	Msg_type	Msg_text

--- a/mysql-test/suite/innodb/t/change_column_collation.test
+++ b/mysql-test/suite/innodb/t/change_column_collation.test
 --source include/have_innodb.inc
+--source include/have_debug.inc
+--source include/have_debug_sync.inc
+--source include/count_sessions.inc
 --echo #
 --echo # MDEV-26294 Duplicate entries in unique index not detected when
@@ -14,11 +18,108 @@ CREATE TABLE t1 (
 ) ENGINE=INNODB;
 INSERT INTO t1 VALUES (1, 'aaa');
 INSERT INTO t1 VALUES (2, 'ååå');
+--error ER_DUP_ENTRY
+ALTER TABLE t1 MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci, ALGORITHM=inplace;
+DROP TABLE t1;
+# PageBulk insert shouldn't fail like records are not in ascending order
+CREATE TABLE t1 (
+  id INT PRIMARY KEY,
+  msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_bin,
+  id_2 INT not null,
+  unique index(msg, id_2)
+) ENGINE=INNODB;
+INSERT INTO t1 VALUES (1, 'aaa', 2);
+INSERT INTO t1 VALUES (2, 'AAA', 3);
+ALTER TABLE t1 MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci, ALGORITHM=inplace;
+DROP TABLE t1;
+# Detect the duplicate entry from concurrent DML
+CREATE TABLE t1 (
+  id INT PRIMARY KEY,
+  msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_bin,
+  unique index(msg)
+) ENGINE=INNODB;
+INSERT INTO t1 VALUES (1, 'aaa');
+INSERT INTO t1 VALUES (2, 'bbb');
+INSERT INTO t1 VALUES (3, 'ccc');
+SET DEBUG_SYNC = 'RESET';
+SET DEBUG_SYNC = 'row_log_apply_before SIGNAL before_apply WAIT_FOR go_ahead';
+--send
+ALTER TABLE t1 MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci, ALGORITHM=NOCOPY;
+connect (con1,localhost,root,,);
+connection con1;
+SET DEBUG_SYNC = 'now WAIT_FOR before_apply';
+INSERT INTO t1 VALUES (4, 'AAA');
+UPDATE t1 set msg = "ddd" where id = 2;
+DELETE FROM t1 WHERE id= 3;
+SET DEBUG_SYNC = 'now SIGNAL go_ahead';
+SET DEBUG_SYNC = 'RESET';
+connection default;
+--error ER_DUP_ENTRY
+reap;
+SELECT * FROM t1;
+DROP TABLE t1;
+# InnoDB should store the changed collation column into
+# change_col_info in index when rollback of alter happens
+CREATE TABLE t1 (
+  id INT PRIMARY KEY,
+  msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_bin,
+  unique index(msg)
+) ENGINE=INNODB;
+INSERT INTO t1 VALUES (1, 'aaa');
+SET DEBUG_DBUG="+d,create_index_fail";
+SET DEBUG_SYNC="innodb_inplace_alter_table_enter SIGNAL con1_go WAIT_FOR alter_signal";
+--send
+ALTER TABLE t1 MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci, ALGORITHM=NOCOPY;
+connection con1;
+SET DEBUG_SYNC="now WAIT_FOR con1_go";
+BEGIN;
+SELECT * FROM t1;
+SET DEBUG_SYNC="now SIGNAL alter_signal";
+connection default;
+--error ER_DUP_ENTRY
+reap;
+connection con1;
+rollback;
+INSERT INTO t1 VALUES(2, 'bbb');
+disconnect con1;
+connection default;
+SET DEBUG_SYNC=reset;
+SHOW CREATE TABLE t1;
+INSERT INTO t1 VALUES(3, 'ccc');
+DROP TABLE t1;
+# Inplace Collation change is not supported for virtual column
+# and stored column
+CREATE TABLE t1(id INT PRIMARY KEY, msg VARCHAR(100),
+		msg_1 VARCHAR(100) AS (msg) VIRTUAL,
+		msg_2 VARCHAR(100) AS (msg) STORED,
+		UNIQUE(msg), UNIQUE(msg_1),
+		UNIQUE(msg_2))ENGINE=InnoDB;
+--error ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMN
+ALTER TABLE t1 MODIFY msg_1 VARCHAR(100) CHARACTER SET utf8
+		COLLATE utf8_unicode_ci, ALGORITHM=inplace;
 --error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
-ALTER TABLE t1
+ALTER TABLE t1 MODIFY msg_2 VARCHAR(100) CHARACTER SET utf8
-MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci,
+                COLLATE utf8_unicode_ci, ALGORITHM=inplace;
-ALGORITHM=NOCOPY;
-ALTER TABLE t1 DROP INDEX msg,
-MODIFY msg VARCHAR(100) CHARACTER SET utf8 COLLATE utf8_unicode_ci,
-ALGORITHM=NOCOPY;
 DROP TABLE t1;
+--source include/wait_until_count_sessions.inc
--- a/mysql-test/suite/innodb/t/instant_alter_charset.test
+++ b/mysql-test/suite/innodb/t/instant_alter_charset.test
@@ -227,18 +227,9 @@ create table key_part_bug (
  a varchar(150) charset utf8mb3 unique key
 ) engine=innodb;
--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
 alter table key_part_bug
  modify a varchar(150) charset utf8mb4,
  algorithm=instant;
--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
-alter table key_part_bug
-  modify a varchar(150) charset utf8mb4,
-  algorithm=nocopy;
-alter table key_part_bug
-  drop index a,
-  modify a varchar(150) charset utf8mb4,
-  algorithm=nocopy;
 drop table key_part_bug;
@@ -356,13 +347,10 @@ check table t;
 alter table t modify c char(100) collate utf8mb4_general_ci, algorithm=instant;
 check table t;
--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
 alter table t modify aa char(10) collate utf8mb4_general_ci, algorithm=instant;
 check table t;
--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
 alter table t modify bb char(70) collate utf8mb4_general_ci, algorithm=instant;
 check table t;
--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
 alter table t modify cc char(100) collate utf8mb4_general_ci, algorithm=instant;
 check table t;
@@ -454,16 +442,11 @@ while ($counter <= $data_size) {
  insert into tmp values ('AAA', 'AAA'), ('bbb', 'bbb');
--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
  eval alter table tmp
    change a a varchar(50) charset $to_charset collate $to_collate,
    modify b varchar(50) charset $to_charset collate $to_collate,
    algorithm=instant;
-  eval alter table tmp
-    change a a varchar(50) charset $to_charset collate $to_collate,
-    algorithm=instant;
  check table tmp;
  drop table tmp;
@@ -702,10 +685,7 @@ alter table t modify a char(10) collate latin1_general_cs, algorithm=inplace;
 --error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
 alter table t modify b char(10) collate latin1_general_cs, algorithm=instant;
--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
 alter table t modify b char(10) collate latin1_general_cs, algorithm=nocopy;
-alter table t modify b char(10) collate latin1_general_cs,
-drop index b_key, algorithm=nocopy;
 check table t;
 alter table t modify c char(10) collate latin1_general_cs, algorithm=instant;
@@ -728,10 +708,7 @@ alter table t modify a varchar(10) collate latin1_general_cs, algorithm=inplace;
 --error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
 alter table t modify b varchar(10) collate latin1_general_cs, algorithm=instant;
--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
 alter table t modify b varchar(10) collate latin1_general_cs, algorithm=nocopy;
-alter table t modify b varchar(10) collate latin1_general_cs,
-drop index b_key, algorithm=nocopy;
 check table t;
 alter table t modify c varchar(10) collate latin1_general_cs, algorithm=instant;

--- a/storage/innobase/handler/handler0alter.cc
+++ b/storage/innobase/handler/handler0alter.cc
@@ -956,6 +956,41 @@ get_error_key_name(
 	}
 }
+/** Convert field type and length to InnoDB format */
+static void get_type(const Field &f, uint &prtype, uint8_t &mtype,
+                     uint16_t &len)
+{
+  mtype= get_innobase_type_from_mysql_type(&prtype, &f);
+  len= static_cast<uint16_t>(f.pack_length());
+  prtype|= f.type();
+  if (f.type() == MYSQL_TYPE_VARCHAR)
+  {
+    auto l= static_cast<const Field_varstring&>(f).length_bytes;
+    len= static_cast<uint16_t>(len - l);
+    if (l == 2)
+      prtype|= DATA_LONG_TRUE_VARCHAR;
+  }
+  if (!f.real_maybe_null())
+    prtype |= DATA_NOT_NULL;
+  if (f.binary())
+    prtype |= DATA_BINARY_TYPE;
+  if (f.table->versioned())
+  {
+    if (&f == f.table->field[f.table->s->vers.start_fieldno])
+      prtype|= DATA_VERS_START;
+    else if (&f == f.table->field[f.table->s->vers.end_fieldno])
+      prtype|= DATA_VERS_END;
+    else if (!(f.flags & VERS_UPDATE_UNVERSIONED_FLAG))
+      prtype|= DATA_VERSIONED;
+  }
+  if (!f.stored_in_db())
+    prtype|= DATA_VIRTUAL;
+  if (dtype_is_string_type(mtype))
+    prtype|= f.charset()->number << 16;
+}
 struct ha_innobase_inplace_ctx : public inplace_alter_handler_ctx
 {
 	/** Dummy query graph */
@@ -1050,6 +1085,10 @@ struct ha_innobase_inplace_ctx : public inplace_alter_handler_ctx
 	/** The page_compression_level attribute, or 0 */
 	const uint	page_compression_level;
+	/** Indexed columns whose charset-collation is changing
+	in a way that does not require the table to be rebuilt */
+	col_collations change_col_collate;
 	ha_innobase_inplace_ctx(row_prebuilt_t*& prebuilt_arg,
 				dict_index_t** drop_arg,
 				ulint num_to_drop_arg,
@@ -1332,6 +1371,85 @@ struct ha_innobase_inplace_ctx : public inplace_alter_handler_ctx
    }
    return true;
  }
+  /** Check whether the column has any change in collation type.
+  If it is then store the column information in heap
+  @param index          index being added (or rebuilt)
+  @param altered_table  altered table definition */
+  void change_col_collation(dict_index_t *index, const TABLE &altered_table)
+  {
+    ut_ad(!need_rebuild());
+    ut_ad(!index->is_primary());
+    ut_ad(!index->is_committed());
+    unsigned n_cols= 0;
+    for (unsigned i= 0; i < index->n_fields; i++)
+    {
+      const char *field_name= index->fields[i].name();
+      if (!field_name || !dtype_is_string_type(index->fields[i].col->mtype))
+        continue;
+      for (uint j= 0; j < altered_table.s->fields; j++)
+      {
+        const Field *altered_field= altered_table.field[j];
+        if (my_strcasecmp(system_charset_info, field_name,
+                          altered_field->field_name.str))
+          continue;
+        unsigned prtype;
+        uint8_t mtype;
+        uint16_t len;
+        get_type(*altered_field, prtype, mtype, len);
+        if (prtype == index->fields[i].col->prtype)
+          continue;
+        auto it= change_col_collate.find(index->fields[i].col->ind);
+        if (it != change_col_collate.end())
+        {
+          n_cols++;
+          index->fields[i].col= it->second;
+          continue;
+        }
+        const CHARSET_INFO *cs= altered_field->charset();
+        dict_col_t *col=
+          static_cast<dict_col_t*>(mem_heap_alloc(heap, sizeof *col));
+        *col= *index->fields[i].col;
+        col->prtype= prtype;
+        col->mtype= mtype;
+        col->mbminlen= cs->mbminlen & 7;
+        col->mbmaxlen= cs->mbmaxlen & 7;
+        col->len= len;
+        index->fields[i].col= col;
+        n_cols++;
+        change_col_collate[col->ind]= col;
+      }
+    }
+    index->init_change_cols(n_cols);
+  }
+  void cleanup_col_collation()
+  {
+    ut_ad(old_table == new_table);
+    if (change_col_collate.empty())
+      return;
+    const dict_index_t *index= dict_table_get_first_index(old_table);
+    while ((index= dict_table_get_next_index(index)) != nullptr)
+    {
+      if (index->is_committed())
+        continue;
+      auto collate_end= change_col_collate.end();
+      for (unsigned i= 0, j= 0; i < index->n_fields; i++)
+      {
+        const dict_col_t *col= index->fields[i].col;
+        if (change_col_collate.find(col->ind) == collate_end)
+          index->fields[i].col=
+            index->change_col_info->add(index->heap, *col, j++);
+      }
+    }
+  }
 };
 /********************************************************************//**
@@ -2345,18 +2463,9 @@ ha_innobase::check_if_supported_inplace_alter(
 			if (new_field->field) {
 				/* This is an existing column. */
-				if (new_field->field->charset()
-				    == key_part->field->charset()) {
 				continue;
 			}
-				ha_alter_info->unsupported_reason =
-					"Collation change on"
-					" an indexed column";
-				DBUG_RETURN(HA_ALTER_INPLACE_NOT_SUPPORTED);
-			}
 			/* This is an added column. */
 			DBUG_ASSERT(ha_alter_info->handler_flags
 				    & ALTER_ADD_COLUMN);
@@ -7061,6 +7170,8 @@ prepare_inplace_alter_table_dict(
 			if (n_v_col) {
 				index->assign_new_v_col(n_v_col);
 			}
+			ctx->change_col_collation(index, *altered_table);
 			/* Note the id of the transaction that created this
 			index, we use it to restrict readers from accessing
 			this index, to ensure read consistency. */
@@ -8533,7 +8644,9 @@ ha_innobase::inplace_alter_table(
 		ctx->add_index, ctx->add_key_numbers, ctx->num_to_add_index,
 		altered_table, ctx->defaults, ctx->col_map,
 		ctx->add_autoinc, ctx->sequence, ctx->skip_pk_sort,
-		ctx->m_stage, add_v, eval_table, ctx->allow_not_null);
+		ctx->m_stage, add_v, eval_table, ctx->allow_not_null,
+		ctx->change_col_collate.empty()
+		? nullptr : &ctx->change_col_collate);
 #ifndef DBUG_OFF
 oom:
@@ -8867,6 +8980,7 @@ inline bool rollback_inplace_alter_table(Alter_inplace_info *ha_alter_info,
                                  Alter_info::ALTER_TABLE_LOCK_EXCLUSIVE,
                                  ctx->trx, prebuilt->trx);
      ctx->clean_new_vcol_index();
+      ctx->cleanup_col_collation();
      ut_d(dict_table_check_for_dup_indexes(ctx->old_table, CHECK_ABORTED_OK));
    }
@@ -9265,36 +9379,6 @@ innobase_rename_columns_try(
 	return(false);
 }
-/** Convert field type and length to InnoDB format */
-static void get_type(const Field& f, uint& prtype, uint8_t& mtype,
-                     uint16_t& len)
-{
-	mtype = get_innobase_type_from_mysql_type(&prtype, &f);
-	len = static_cast<uint16_t>(f.pack_length());
-	prtype |= f.type();
-	if (f.type() == MYSQL_TYPE_VARCHAR) {
-		auto l = static_cast<const Field_varstring&>(f).length_bytes;
-		len = static_cast<uint16_t>(len - l);
-		if (l == 2) prtype |= DATA_LONG_TRUE_VARCHAR;
-	}
-	if (!f.real_maybe_null()) prtype |= DATA_NOT_NULL;
-	if (f.binary()) prtype |= DATA_BINARY_TYPE;
-	if (f.table->versioned()) {
-		if (&f == f.table->field[f.table->s->vers.start_fieldno]) {
-			prtype |= DATA_VERS_START;
-		} else if (&f == f.table->field[f.table->s->vers.end_fieldno]) {
-			prtype |= DATA_VERS_END;
-		} else if (!(f.flags & VERS_UPDATE_UNVERSIONED_FLAG)) {
-			prtype |= DATA_VERSIONED;
-		}
-	}
-	if (!f.stored_in_db()) prtype |= DATA_VIRTUAL;
-	if (dtype_is_string_type(mtype)) {
-		prtype |= f.charset()->number << 16;
-	}
-}
 /** Enlarge a column in the data dictionary tables.
 @param ctx In-place ALTER TABLE context
 @param trx data dictionary transaction
@@ -10617,6 +10701,7 @@ commit_cache_norebuild(
 		DBUG_ASSERT(dict_index_get_online_status(index)
 			    == ONLINE_INDEX_COMPLETE);
 		DBUG_ASSERT(!index->is_committed());
+		index->change_col_info = nullptr;
 		index->set_committed(true);
 	}
@@ -11368,7 +11453,8 @@ ha_innobase::commit_inplace_alter_table(
 		    || ha_alter_info->alter_info->create_list.elements))
 	    || (ctx0->is_instant()
 		&& m_prebuilt->table->n_v_cols
-		&& ha_alter_info->handler_flags & ALTER_STORED_COLUMN_ORDER)) {
+		&& ha_alter_info->handler_flags & ALTER_STORED_COLUMN_ORDER)
+	    || !ctx0->change_col_collate.empty()) {
 		DBUG_ASSERT(ctx0->old_table->get_ref_count() == 1);
 		ut_ad(ctx0->prebuilt == m_prebuilt);

--- a/storage/innobase/include/data0data.h
+++ b/storage/innobase/include/data0data.h
 /*****************************************************************************
 Copyright (c) 1994, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2019, 2020 MariaDB Corporation.
+Copyright (c) 2017, 2022, MariaDB Corporation.
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -581,6 +581,10 @@ struct dtuple_t {
 	/** @return whether this is a hidden metadata record
 	for instant ADD COLUMN or ALTER TABLE */
 	bool is_metadata() const { return is_metadata(info_bits); }
+	/** Copy type information from index fields.
+	@param index	index field to be copied */
+	inline void copy_field_types(const dict_index_t &index);
 };
 inline ulint dtuple_get_n_fields(const dtuple_t* tuple)

--- a/storage/innobase/include/data0type.h
+++ b/storage/innobase/include/data0type.h
@@ -488,6 +488,8 @@ dtype_print(
 	const dtype_t*	type);
 #endif /* UNIV_DEBUG */
+struct dict_col_t;
 /* Structure for an SQL data type.
 If you add fields to this structure, be sure to initialize them everywhere.
 This structure is initialized in the following functions:
@@ -543,6 +545,10 @@ struct dtype_t{
 		mbminlen = 0;
 		mbmaxlen = 0;
 	}
+	/** Copy the type information from a column.
+	@param col column type to be copied */
+	void assign(const dict_col_t &col);
 };
 /** The DB_TRX_ID,DB_ROLL_PTR values for "no history is available" */

--- a/storage/innobase/include/dict0mem.h
+++ b/storage/innobase/include/dict0mem.h
@@ -966,6 +966,26 @@ const char innobase_index_reserve_name[] = "GEN_CLUST_INDEX";
 /** Data structure for an index.  Most fields will be
 initialized to 0, NULL or FALSE in dict_mem_index_create(). */
 struct dict_index_t {
+  /** Columns whose character-set collation is being changed */
+  struct col_info
+  {
+    /** number of columns whose charset-collation is being changed */
+    unsigned n_cols;
+    /** columns with changed charset-collation */
+    dict_col_t *cols;
+    /** Add a column with changed collation. */
+    dict_col_t *add(mem_heap_t *heap, const dict_col_t &col, unsigned offset)
+    {
+      ut_ad(offset < n_cols);
+      if (!cols)
+        cols= static_cast<dict_col_t*>
+          (mem_heap_alloc(heap, n_cols * sizeof col));
+      new (&cols[offset]) dict_col_t(col);
+      return &cols[offset];
+    }
+  };
  /** Maximum number of fields */
  static constexpr unsigned MAX_N_FIELDS= (1U << 10) - 1;
@@ -1051,6 +1071,16 @@ struct dict_index_t {
 	It should use heap from dict_index_t. It should be freed
 	while removing the index from table. */
 	dict_add_v_col_info* new_vcol_info;
+	/** During ALTER TABLE, columns that a being-added index depends on
+	and whose encoding or collation is being changed to something
+	that is compatible with the clustered index.
+	Allocated from dict_index_t::heap.
+	@see rollback_inplace_alter_table()
+	@see ha_innobase_inplace_ctx::col_collations */
+	col_info* change_col_info;
 	UT_LIST_NODE_T(dict_index_t)
 			indexes;/*!< list of indexes of the table */
 #ifdef BTR_CUR_ADAPT
@@ -1145,6 +1175,7 @@ struct dict_index_t {
 	{
 		ut_ad(!to_be_dropped);
 		ut_ad(committed || !(type & DICT_CLUSTERED));
+		ut_ad(!committed || !change_col_info);
 		uncommitted = !committed;
 	}
@@ -1310,6 +1341,16 @@ struct dict_index_t {
  ulint get_new_n_vcol() const
  { return new_vcol_info ? new_vcol_info->n_v_col : 0; }
+  /** Assign the number of collation change fields as a part of the index
+  @param  n_cols   number of columns whose collation is changing */
+  void init_change_cols(unsigned n_cols)
+  {
+    ut_ad(n_fields > n_cols);
+    change_col_info= static_cast<col_info*>
+      (mem_heap_zalloc(heap, sizeof(col_info)));
+    change_col_info->n_cols= n_cols;
+  }
  /** Reconstruct the clustered index fields.
  @return whether metadata is incorrect */
  inline bool reconstruct_fields();

--- a/storage/innobase/include/row0merge.h
+++ b/storage/innobase/include/row0merge.h
 /*****************************************************************************
 Copyright (c) 2005, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2015, 2021, MariaDB Corporation.
+Copyright (c) 2015, 2022, MariaDB Corporation.
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -216,6 +216,11 @@ row_merge_is_index_usable(
 	const dict_index_t*	index)	/*!< in: index to check */
 	MY_ATTRIBUTE((nonnull, warn_unused_result));
+/** Map from column numbers to column definitions that include
+changes to the collation, when the encoding is compatible with
+the original column and no table rebuild is needed */
+typedef std::map<unsigned, dict_col_t*> col_collations;
 /** Build indexes on a table by reading a clustered index, creating a temporary
 file containing index entries, merge sorting these index entries and inserting
 sorted index entries to indexes.
@@ -244,6 +249,7 @@ this function and it will be passed to other functions for further accounting.
 @param[in]	eval_table	mysql table used to evaluate virtual column
 				value, see innobase_get_computed_value().
 @param[in]	allow_non_null	allow the conversion from null to not-null
+@param[in]	col_collate	columns whose collations changed, or nullptr
 @return DB_SUCCESS or error code */
 dberr_t
 row_merge_build_indexes(
@@ -263,7 +269,8 @@ row_merge_build_indexes(
 	ut_stage_alter_t*	stage,
 	const dict_add_v_col_t*	add_v,
 	struct TABLE*		eval_table,
-	bool			allow_non_null)
+	bool			allow_non_null,
+	const col_collations*	col_collate)
 	MY_ATTRIBUTE((warn_unused_result));
 /********************************************************************//**

--- a/storage/innobase/row/row0log.cc
+++ b/storage/innobase/row/row0log.cc
@@ -3877,6 +3877,23 @@ static void row_log_mark_other_online_index_abort(dict_table_t *table)
  table->drop_aborted= TRUE;
 }
+void dtype_t::assign(const dict_col_t &col)
+{
+  prtype= col.prtype;
+  mtype= col.mtype;
+  len= col.len;
+  mbminlen= col.mbminlen;
+  mbmaxlen= col.mbmaxlen;
+}
+inline void dtuple_t::copy_field_types(const dict_index_t &index)
+{
+  ut_ad(index.n_fields == n_fields);
+  if (UNIV_LIKELY_NULL(index.change_col_info))
+    for (ulint i= 0; i < n_fields; i++)
+      fields[i].type.assign(*index.fields[i].col);
+}
 void UndorecApplier::log_insert(const dtuple_t &tuple,
                                dict_index_t *clust_index)
 {
@@ -3943,6 +3960,7 @@ void UndorecApplier::log_insert(const dtuple_t &tuple,
      {
        dtuple_t *entry= row_build_index_entry_low(row, ext, index,
                                                   heap, ROW_BUILD_NORMAL);
+        entry->copy_field_types(*index);
 	success= row_log_online_op(index, entry, trx_id);
      }
@@ -4069,11 +4087,15 @@ void UndorecApplier::log_update(const dtuple_t &tuple,
        dtuple_t *old_entry= row_build_index_entry_low(
          old_row, old_ext, index, heap, ROW_BUILD_NORMAL);
+        old_entry->copy_field_types(*index);
 	success= row_log_online_op(index, old_entry, 0);
 	dtuple_t *new_entry= row_build_index_entry_low(
          row, new_ext, index, heap, ROW_BUILD_NORMAL);
+        new_entry->copy_field_types(*index);
 	if (success)
 	  success= row_log_online_op(index, new_entry, trx_id);
      }
@@ -4082,6 +4104,8 @@ void UndorecApplier::log_update(const dtuple_t &tuple,
        dtuple_t *old_entry= row_build_index_entry_low(
          row, new_ext, index, heap, ROW_BUILD_NORMAL);
+        old_entry->copy_field_types(*index);
        success= row_log_online_op(index, old_entry, 0);
      }
    }

--- a/storage/innobase/row/row0merge.cc
+++ b/storage/innobase/row/row0merge.cc
@@ -490,6 +490,7 @@ row_merge_buf_redundant_convert(
 @param[in,out]	v_heap		heap memory to process data for virtual column
 @param[in,out]	my_table	mysql table object
 @param[in]	trx		transaction object
+@param[in]	col_collate	columns whose collations changed, or nullptr
 @return number of rows added, 0 if out of space */
 static
 ulint
@@ -506,7 +507,8 @@ row_merge_buf_add(
 	dberr_t*		err,
 	mem_heap_t**		v_heap,
 	TABLE*			my_table,
-	trx_t*			trx)
+	trx_t*			trx,
+	const col_collations*	col_collate)
 {
 	ulint			i;
 	const dict_index_t*	index;
@@ -520,6 +522,7 @@ row_merge_buf_add(
 	doc_id_t		write_doc_id;
 	ulint			n_row_added = 0;
 	VCOL_STORAGE		vcol_storage;
 	DBUG_ENTER("row_merge_buf_add");
 	if (buf->n_tuples >= buf->max_tuples) {
@@ -611,8 +614,17 @@ row_merge_buf_add(
 				row_field = dtuple_get_nth_field(row,
 								 col->ind);
 				dfield_copy(field, row_field);
-			}
+				/* Copy the column collation to the
+				tuple field */
+				if (col_collate) {
+					auto it = col_collate->find(col->ind);
+					if (it != col_collate->end()) {
+						field->type
+							.assign(*it->second);
+					}
+				}
+			}
 			/* Tokenize and process data for FTS */
 			if (index->type & DICT_FTS) {
@@ -1657,6 +1669,7 @@ stage->inc() will be called for each page read.
 @param[in]	eval_table	mysql table used to evaluate virtual column
 				value, see innobase_get_computed_value().
 @param[in]	allow_not_null	allow null to not-null conversion
+@param[in]	col_collate	columns whose collations changed, or nullptr
 @return DB_SUCCESS or error */
 static MY_ATTRIBUTE((warn_unused_result))
 dberr_t
@@ -1684,7 +1697,8 @@ row_merge_read_clustered_index(
 	double 			pct_cost,
 	row_merge_block_t*	crypt_block,
 	struct TABLE*		eval_table,
-	bool			allow_not_null)
+	bool			allow_not_null,
+	const col_collations*	col_collate)
 {
 	dict_index_t*		clust_index;	/* Clustered index */
 	mem_heap_t*		row_heap = NULL;/* Heap memory to create
@@ -2391,7 +2405,8 @@ row_merge_read_clustered_index(
 					buf, fts_index, old_table, new_table,
 					psort_info, row, ext, &doc_id,
 					conv_heap, &err,
-					&v_heap, eval_table, trx)))) {
+					&v_heap, eval_table, trx,
+					col_collate)))) {
 				/* If we are creating FTS index,
 				a single row can generate more
@@ -2718,7 +2733,8 @@ row_merge_read_clustered_index(
 						buf, fts_index, old_table,
 						new_table, psort_info, row, ext,
 						&doc_id, conv_heap,
-						&err, &v_heap, eval_table, trx)))) {
+						&err, &v_heap, eval_table,
+						trx, col_collate)))) {
                                        /* An empty buffer should have enough
                                        room for at least one record. */
 					ut_ad(err == DB_COMPUTE_VALUE_FAILED
@@ -4422,6 +4438,7 @@ this function and it will be passed to other functions for further accounting.
 @param[in]	eval_table	mysql table used to evaluate virtual column
 				value, see innobase_get_computed_value().
 @param[in]	allow_not_null	allow the conversion from null to not-null
+@param[in]	col_collate	columns whose collations changed, or nullptr
 @return DB_SUCCESS or error code */
 dberr_t
 row_merge_build_indexes(
@@ -4441,7 +4458,8 @@ row_merge_build_indexes(
 	ut_stage_alter_t*	stage,
 	const dict_add_v_col_t*	add_v,
 	struct TABLE*		eval_table,
-	bool			allow_not_null)
+	bool			allow_not_null,
+	const col_collations*	col_collate)
 {
 	merge_file_t*		merge_files;
 	row_merge_block_t*	block;
@@ -4591,7 +4609,8 @@ row_merge_build_indexes(
 		fts_sort_idx, psort_info, merge_files, key_numbers,
 		n_indexes, defaults, add_v, col_map, add_autoinc,
 		sequence, block, skip_pk_sort, &tmpfd, stage,
-		pct_cost, crypt_block, eval_table, allow_not_null);
+		pct_cost, crypt_block, eval_table, allow_not_null,
+		col_collate);
 	stage->end_phase_read_pk();

--- a/storage/innobase/row/row0mysql.cc
+++ b/storage/innobase/row/row0mysql.cc
@@ -823,6 +823,10 @@ row_create_prebuilt(
 		DBUG_EXECUTE_IF("innodb_srch_key_buffer_max_value",
 			ut_a(temp_index->n_user_defined_cols
 						== MAX_REF_PARTS););
+		if (temp_index->is_corrupted()) {
+			continue;
+		}
 		uint temp_len = 0;
 		for (uint i = 0; i < temp_index->n_uniq; i++) {
 			ulint type = temp_index->fields[i].col->mtype;