From c411ba78bc6ce59511076d4753baf6bb5a42e65f Mon Sep 17 00:00:00 2001
From: Simoffsky <maks-kirsanov26@mail.ru>
Date: Mon, 30 Dec 2024 22:36:43 +1000
Subject: [PATCH 1/6] MDEV-12302 Execute triggers for foreign key
 updates/deletes

---
 .../suite/innodb/r/trigger_cascade.result     | 382 ++++++++++++++++
 .../suite/innodb/t/trigger_cascade.test       | 418 ++++++++++++++++++
 sql/sql_base.cc                               |  15 +-
 sql/sql_table.cc                              |  91 ++++
 sql/sql_table.h                               |   3 +
 storage/innobase/handler/ha_innodb.cc         | 242 +++++++++-
 storage/innobase/handler/ha_innodb.h          |  19 +-
 storage/innobase/include/row0sel.h            |  19 +
 storage/innobase/row/row0mysql.cc             |   9 +-
 storage/innobase/row/row0sel.cc               |  95 ++--
 storage/innobase/ut/ut0ut.cc                  |   1 -
 11 files changed, 1236 insertions(+), 58 deletions(-)
 create mode 100644 mysql-test/suite/innodb/r/trigger_cascade.result
 create mode 100644 mysql-test/suite/innodb/t/trigger_cascade.test

diff --git a/mysql-test/suite/innodb/r/trigger_cascade.result b/mysql-test/suite/innodb/r/trigger_cascade.result
new file mode 100644
index 0000000000000..a0f7e8ac4b0f6
--- /dev/null
+++ b/mysql-test/suite/innodb/r/trigger_cascade.result
@@ -0,0 +1,382 @@
+#
+# After update
+#
+create table t1 (
+x int primary key
+) engine=innodb;
+create table t2 (
+x int primary key,
+y int,
+foreign key (x) references t1(x) on update cascade
+) engine=innodb;
+create table t3 (
+old_x int,
+new_x int
+) engine=innodb;
+create trigger tr after update on t2
+for each row
+insert into t3 (old_x, new_x) values (old.x, new.x);
+insert into t1 (x) values (1);
+insert into t2 (x, y) values (1, 20);
+update t1 set x = 2;
+select * from t3;
+old_x	new_x
+1	2
+update t2 set y = 50;
+select * from t3;
+old_x	new_x
+1	2
+2	2
+select * from t1;
+x
+2
+select * from t2;
+x	y
+2	50
+drop table t3;
+drop table t2;
+drop table t1;
+#
+# After update with counter
+#
+create table t1(x int primary key) engine=innodb;
+create table t2(x int primary key,
+foreign key(x) references t1(x) on update cascade) engine=innodb;
+create trigger tr_t2 after update on t2
+for each row set @counter=@counter+1;
+insert into t1 values (1);
+insert into t2 values (1);
+set @counter=0;
+update t1 set x = 2;
+select * from t1;
+x
+2
+select * from t2;
+x
+2
+select @counter;
+@counter
+1
+drop table t2;
+drop table t1;
+#
+# Before update
+#
+create table t1 (
+x int primary key
+) engine=innodb;
+create table t2 (
+x int primary key,
+y int,
+foreign key(x) references t1(x) on update cascade
+) engine=innodb;
+create trigger tr before update on t2
+for each row set new.y = 50;
+insert into t1 (x) values (1);
+insert into t2 (x, y) values (1,2);
+update t1 set x = 2;
+select * from t1;
+x
+2
+select * from t2;
+x	y
+2	50
+drop table t2;
+drop table t1;
+#
+# Update, foreign key on secondary index
+#
+create table t1(x int auto_increment primary key, y int, unique key(y)) engine=innodb;
+create table t2(a int primary key, x int, z varchar(20),
+foreign key(x) references t1(y) on update cascade) engine=innodb;
+create table t3(id int auto_increment primary key, action_x int, action_z varchar(20), note varchar(50)) engine=innodb;
+create trigger tr_t2 before update on t2
+for each row
+insert into t3(action_x, action_z, note) values (old.x, old.z, 'update t2 — old'),
+(new.x, new.z, 'update t2 — new');
+insert into t1 values (1, 10);
+insert into t2 values (1, 10, 'str');
+update t1 set y=20 where x=1;
+select * from t1;
+x	y
+1	20
+select * from t2;
+a	x	z
+1	20	str
+select * from t3;
+id	action_x	action_z	note
+1	10	str	update t2 — old
+2	20	str	update t2 — new
+drop table t3;
+drop table t2;
+drop table t1;
+#
+# Update, on update set null cascade
+#
+create table t1 (
+id int primary key,
+value varchar(50)
+) engine=innodb;
+create table t2 (
+id int primary key,
+t1_id int,
+t2_value varchar(50),
+foreign key (t1_id) references t1(id) on update set null
+) engine=innodb;
+create trigger tr_t2_before_update before update on t2
+for each row set new.t2_value = 'updated by trigger';
+insert into t1 (id, value) values (1, 'parent_row');
+insert into t2 (id, t1_id, t2_value) values (1, 1, 'child_row');
+select * from t1;
+id	value
+1	parent_row
+select * from t2;
+id	t1_id	t2_value
+1	1	child_row
+update t1 set id = 2 where id = 1;
+select * from t1;
+id	value
+2	parent_row
+select * from t2;
+id	t1_id	t2_value
+1	NULL	updated by trigger
+drop table t2;
+drop table t1;
+#
+# Before update, indexes on virtual columns
+#
+create table t1(x int auto_increment primary key, y int, unique key(y)) engine=innodb;
+create table t2(a int primary key, x int,
+t int,
+z varchar(20) as (concat("test", t)),
+y varchar(20) as (concat("test2", t)),
+y_another varchar(20) as (concat("test3", x)),
+unique(z),
+unique(y),
+unique(y_another),
+foreign key(x) references t1(y) on update cascade) engine=innodb;
+create trigger tr before update on t2
+for each row set new.t = 50;
+insert into t1 (x,y) values (1,1);
+insert into t2 (a,x,t) values (1,1,1);
+select * from t2;
+a	x	t	z	y	y_another
+1	1	1	test1	test21	test31
+update t1 set y = 2;
+select * from t2 force index (z) where z = 'test50';
+a	x	t	z	y	y_another
+1	2	50	test50	test250	test32
+select * from t2 force index (y) where y = 'test250';
+a	x	t	z	y	y_another
+1	2	50	test50	test250	test32
+select * from t2 force index (y_another) where y_another = 'test32';
+a	x	t	z	y	y_another
+1	2	50	test50	test250	test32
+select * from t2;
+a	x	t	z	y	y_another
+1	2	50	test50	test250	test32
+drop table t2;
+drop table t1;
+#
+# Before delete
+#
+create table t1 (
+x int primary key
+) engine=innodb;
+create table t2 (
+x int primary key,
+y int,
+foreign key(x) references t1(x) on delete cascade
+) engine=innodb;
+create trigger tr before delete on t2
+for each row set @deleted_value = old.y;
+insert into t1 (x) values (1);
+insert into t2 (x, y) values (1, 100);
+delete from t1 where x = 1;
+select @deleted_value as deleted_value;
+deleted_value
+100
+select * from t2;
+x	y
+drop table t2;
+drop table t1;
+#
+# After, before delete
+#
+create table t1 (
+x int primary key
+) engine=innodb;
+create table t2 (
+x int primary key,
+y int,
+foreign key(x) references t1(x) on delete cascade
+) engine=innodb;
+create table t3 (
+id int auto_increment primary key,
+log_event varchar(255)
+) engine=innodb;
+create trigger tr_before before delete on t2
+for each row
+set @deleted_value = old.y;
+create trigger tr_after after delete on t2
+for each row
+insert into t3 (log_event) values ('after delete trigger executed');
+insert into t1 (x) values (1), (2);
+insert into t2 (x, y) values (1, 100), (2, 200);
+delete from t1 where x = 1;
+select @deleted_value as before_deleted_value;
+before_deleted_value
+100
+select * from t3;
+id	log_event
+1	after delete trigger executed
+select * from t2;
+x	y
+2	200
+select * from t1;
+x
+2
+drop table t3;
+drop table t2;
+drop table t1;
+#
+# On delete set null
+#
+create table t1 (
+id int primary key,
+value varchar(50)
+) engine=innodb;
+create table t2 (
+id int primary key,
+t1_id int,
+t2_value varchar(50),
+foreign key (t1_id) references t1(id) on delete set null
+) engine=innodb;
+create trigger tr_t2_before_update before update on t2
+for each row set new.t2_value = 'updated by trigger';
+insert into t1 (id, value) values (1, 'parent_row');
+insert into t2 (id, t1_id, t2_value) values (1, 1, 'child_row');
+select * from t1;
+id	value
+1	parent_row
+select * from t2;
+id	t1_id	t2_value
+1	1	child_row
+delete from t1 where id = 1;
+select * from t1;
+id	value
+select * from t2;
+id	t1_id	t2_value
+1	NULL	updated by trigger
+drop table t2;
+drop table t1;
+#
+# Cascade chain
+#
+create table t1 (
+id int primary key
+) engine=innodb;
+create table t2 (
+id int primary key,
+foreign key (id) references t1(id) on update cascade
+) engine=innodb;
+create table t3 (
+id int primary key,
+foreign key (id) references t2(id) on update cascade
+) engine=innodb;
+create table update_log (
+log_id int auto_increment primary key,
+table_name varchar(50),
+old_value int,
+new_value int
+) engine=innodb;
+create trigger tr_t2_after_update after update on t2
+for each row
+insert into update_log(table_name, old_value, new_value)
+values ('t2', old.id, new.id);
+create trigger tr_t3_after_update after update on t3
+for each row
+insert into update_log(table_name, old_value, new_value)
+values ('t3', old.id, new.id);
+insert into t1 (id) values (1);
+insert into t2 (id) values (1);
+insert into t3 (id) values (1);
+update t1 set id = 2;
+select * from t1;
+id
+2
+select * from t2;
+id
+2
+select * from t3;
+id
+2
+select * from update_log;
+log_id	table_name	old_value	new_value
+1	t3	1	2
+2	t2	1	2
+drop table update_log;
+drop table t3;
+drop table t2;
+drop table t1;
+#
+# With bit fields
+#
+create table t1 (
+id bit(8) primary key,
+flag bit(1) not null default b'0'
+) engine=innodb;
+create table t2 (
+id bit(8) primary key,
+t1_id bit(8),
+value int,
+foreign key (t1_id) references t1(id) on update cascade
+) engine=innodb;
+create table trigger_log (
+log_id int auto_increment primary key,
+log_message varchar(255)
+) engine=innodb;
+create trigger tr_t2_after_update after update on t2
+for each row
+insert into trigger_log(log_message)
+values (concat('t2 updated: ', hex(old.t1_id), ' -> ', hex(new.t1_id)));
+insert into t1 (id, flag) values (b'00000001', b'1');
+insert into t2 (id, t1_id, value) values (b'00000001', b'00000001', 100);
+update t1 set id = b'00000010' where id = b'00000001';
+select bin(id), bin(t1_id), value from t2;
+bin(id)	bin(t1_id)	value
+1	10	100
+select * from trigger_log;
+log_id	log_message
+1	t2 updated: 1 -> 2
+drop table trigger_log;
+drop table t2;
+drop table t1;
+#
+# With blobs
+#
+create table t1 (
+id int primary key,
+blob_data blob
+) engine=innodb;
+create table t2 (
+id int primary key,
+t1_id int,
+copied_blob_data blob,
+foreign key (t1_id) references t1(id) on delete cascade on update cascade
+) engine=innodb;
+create trigger tr_t2_before_update
+before update on t2
+for each row
+set new.copied_blob_data = concat(old.copied_blob_data, repeat('-updated', 1250));
+insert into t1 (id, blob_data) values (1, repeat('a', 1024));
+insert into t2 (id, t1_id, copied_blob_data) values (1, 1, repeat('b', 1024));
+select * from t2;
+id	t1_id	copied_blob_data
+1	1	bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+update t1 set id = 2 where id = 1;
+select * from t2;
+id	t1_id	copied_blob_data
+1	2	bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-up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+drop table t2;
+drop table t1;
diff --git a/mysql-test/suite/innodb/t/trigger_cascade.test b/mysql-test/suite/innodb/t/trigger_cascade.test
new file mode 100644
index 0000000000000..3fba13afc2259
--- /dev/null
+++ b/mysql-test/suite/innodb/t/trigger_cascade.test
@@ -0,0 +1,418 @@
+--source include/have_innodb.inc
+
+--echo #
+--echo # After update
+--echo #
+
+create table t1 (
+    x int primary key
+) engine=innodb;
+
+create table t2 (
+    x int primary key,
+    y int,
+    foreign key (x) references t1(x) on update cascade
+) engine=innodb;
+
+create table t3 (
+    old_x int,
+    new_x int
+) engine=innodb;
+
+create trigger tr after update on t2
+    for each row
+   insert into t3 (old_x, new_x) values (old.x, new.x);
+
+insert into t1 (x) values (1);
+insert into t2 (x, y) values (1, 20);
+
+update t1 set x = 2;
+select * from t3;
+update t2 set y = 50;
+
+select * from t3;
+select * from t1;
+select * from t2;
+
+drop table t3;
+drop table t2;
+drop table t1;
+
+--echo #
+--echo # After update with counter
+--echo #
+
+create table t1(x int primary key) engine=innodb;
+create table t2(x int primary key,
+            foreign key(x) references t1(x) on update cascade) engine=innodb;
+
+create trigger tr_t2 after update on t2
+    for each row set @counter=@counter+1;
+
+insert into t1 values (1);
+insert into t2 values (1);
+set @counter=0;
+
+update t1 set x = 2;
+
+select * from t1;
+select * from t2;
+
+select @counter;
+drop table t2;
+drop table t1;
+
+--echo #
+--echo # Before update
+--echo #
+
+create table t1 (
+    x int primary key
+) engine=innodb;
+
+
+create table t2 (
+    x int primary key,
+    y int,
+    foreign key(x) references t1(x) on update cascade
+) engine=innodb;
+
+create trigger tr before update on t2
+    for each row set new.y = 50;
+
+insert into t1 (x) values (1);
+insert into t2 (x, y) values (1,2);
+
+update t1 set x = 2;
+select * from t1;
+select * from t2;
+
+
+drop table t2;
+drop table t1;
+
+--echo #
+--echo # Update, foreign key on secondary index
+--echo #
+
+create table t1(x int auto_increment primary key, y int, unique key(y)) engine=innodb;
+create table t2(a int primary key, x int, z varchar(20),
+                foreign key(x) references t1(y) on update cascade) engine=innodb;
+create table t3(id int auto_increment primary key, action_x int, action_z varchar(20), note varchar(50)) engine=innodb;
+
+create trigger tr_t2 before update on t2
+    for each row
+        insert into t3(action_x, action_z, note) values (old.x, old.z, 'update t2 — old'),
+        (new.x, new.z, 'update t2 — new');
+
+
+
+insert into t1 values (1, 10);
+insert into t2 values (1, 10, 'str');
+
+update t1 set y=20 where x=1;
+
+select * from t1;
+select * from t2;
+select * from t3;
+
+drop table t3;
+drop table t2;
+drop table t1;
+
+--echo #
+--echo # Update, on update set null cascade
+--echo #
+
+create table t1 (
+    id int primary key,
+    value varchar(50)
+) engine=innodb;
+
+create table t2 (
+    id int primary key,
+    t1_id int,
+    t2_value varchar(50),
+    foreign key (t1_id) references t1(id) on update set null
+) engine=innodb;
+
+create trigger tr_t2_before_update before update on t2
+for each row set new.t2_value = 'updated by trigger';
+
+insert into t1 (id, value) values (1, 'parent_row');
+insert into t2 (id, t1_id, t2_value) values (1, 1, 'child_row');
+
+select * from t1;
+select * from t2;
+
+update t1 set id = 2 where id = 1;
+
+select * from t1;
+select * from t2;
+
+drop table t2;
+drop table t1;
+
+--echo #
+--echo # Before update, indexes on virtual columns
+--echo #
+
+create table t1(x int auto_increment primary key, y int, unique key(y)) engine=innodb;
+create table t2(a int primary key, x int,
+                t int,
+                z varchar(20) as (concat("test", t)),
+                y varchar(20) as (concat("test2", t)),
+                y_another varchar(20) as (concat("test3", x)),
+                unique(z),
+                unique(y),
+                unique(y_another),
+                foreign key(x) references t1(y) on update cascade) engine=innodb;
+
+create trigger tr before update on t2
+    for each row set new.t = 50;
+
+insert into t1 (x,y) values (1,1);
+insert into t2 (a,x,t) values (1,1,1);
+
+select * from t2;
+update t1 set y = 2;
+select * from t2 force index (z) where z = 'test50';
+select * from t2 force index (y) where y = 'test250';
+select * from t2 force index (y_another) where y_another = 'test32';
+select * from t2;
+drop table t2;
+drop table t1;
+
+--echo #
+--echo # Before delete
+--echo #
+
+create table t1 (
+    x int primary key
+) engine=innodb;
+
+create table t2 (
+    x int primary key,
+    y int,
+    foreign key(x) references t1(x) on delete cascade
+) engine=innodb;
+
+create trigger tr before delete on t2
+    for each row set @deleted_value = old.y;
+
+insert into t1 (x) values (1);
+insert into t2 (x, y) values (1, 100);
+
+delete from t1 where x = 1;
+
+select @deleted_value as deleted_value;
+
+select * from t2;
+
+drop table t2;
+drop table t1;
+
+--echo #
+--echo # After, before delete
+--echo #
+
+create table t1 (
+    x int primary key
+) engine=innodb;
+
+create table t2 (
+    x int primary key,
+    y int,
+    foreign key(x) references t1(x) on delete cascade
+) engine=innodb;
+
+create table t3 (
+    id int auto_increment primary key,
+    log_event varchar(255)
+) engine=innodb;
+
+
+create trigger tr_before before delete on t2
+    for each row
+        set @deleted_value = old.y;
+
+
+create trigger tr_after after delete on t2
+    for each row
+        insert into t3 (log_event) values ('after delete trigger executed');
+
+insert into t1 (x) values (1), (2);
+insert into t2 (x, y) values (1, 100), (2, 200);
+
+delete from t1 where x = 1;
+
+select @deleted_value as before_deleted_value;
+
+select * from t3;
+
+select * from t2;
+
+select * from t1;
+
+drop table t3;
+drop table t2;
+drop table t1;
+
+--echo #
+--echo # On delete set null
+--echo #
+
+create table t1 (
+    id int primary key,
+    value varchar(50)
+) engine=innodb;
+
+create table t2 (
+    id int primary key,
+    t1_id int,
+    t2_value varchar(50),
+    foreign key (t1_id) references t1(id) on delete set null
+) engine=innodb;
+
+
+create trigger tr_t2_before_update before update on t2
+for each row set new.t2_value = 'updated by trigger';
+
+insert into t1 (id, value) values (1, 'parent_row');
+insert into t2 (id, t1_id, t2_value) values (1, 1, 'child_row');
+
+select * from t1;
+select * from t2;
+
+delete from t1 where id = 1;
+
+select * from t1;
+select * from t2;
+
+drop table t2;
+drop table t1;
+
+--echo #
+--echo # Cascade chain
+--echo #
+
+create table t1 (
+    id int primary key
+) engine=innodb;
+
+create table t2 (
+    id int primary key,
+    foreign key (id) references t1(id) on update cascade
+) engine=innodb;
+
+create table t3 (
+    id int primary key,
+    foreign key (id) references t2(id) on update cascade
+) engine=innodb;
+
+create table update_log (
+    log_id int auto_increment primary key,
+    table_name varchar(50),
+    old_value int,
+    new_value int
+) engine=innodb;
+
+create trigger tr_t2_after_update after update on t2
+    for each row
+        insert into update_log(table_name, old_value, new_value)
+        values ('t2', old.id, new.id);
+
+create trigger tr_t3_after_update after update on t3
+    for each row
+        insert into update_log(table_name, old_value, new_value)
+        values ('t3', old.id, new.id);
+
+insert into t1 (id) values (1);
+insert into t2 (id) values (1);
+insert into t3 (id) values (1);
+
+update t1 set id = 2;
+
+select * from t1;
+select * from t2;
+select * from t3;
+select * from update_log;
+
+drop table update_log;
+drop table t3;
+drop table t2;
+drop table t1;
+
+--echo #
+--echo # With bit fields
+--echo #
+
+create table t1 (
+    id bit(8) primary key,
+    flag bit(1) not null default b'0'
+) engine=innodb;
+
+create table t2 (
+    id bit(8) primary key,
+    t1_id bit(8),
+    value int,
+    foreign key (t1_id) references t1(id) on update cascade
+) engine=innodb;
+
+create table trigger_log (
+    log_id int auto_increment primary key,
+    log_message varchar(255)
+) engine=innodb;
+
+create trigger tr_t2_after_update after update on t2
+    for each row
+    insert into trigger_log(log_message)
+    values (concat('t2 updated: ', hex(old.t1_id), ' -> ', hex(new.t1_id)));
+
+insert into t1 (id, flag) values (b'00000001', b'1');
+insert into t2 (id, t1_id, value) values (b'00000001', b'00000001', 100);
+
+update t1 set id = b'00000010' where id = b'00000001';
+
+select bin(id), bin(t1_id), value from t2;
+
+select * from trigger_log;
+
+drop table trigger_log;
+drop table t2;
+drop table t1;
+
+
+--echo #
+--echo # With blobs
+--echo #
+
+create table t1 (
+    id int primary key,
+    blob_data blob
+) engine=innodb;
+
+create table t2 (
+    id int primary key,
+    t1_id int,
+    copied_blob_data blob,
+    foreign key (t1_id) references t1(id) on delete cascade on update cascade
+) engine=innodb;
+
+
+create trigger tr_t2_before_update
+before update on t2
+for each row
+set new.copied_blob_data = concat(old.copied_blob_data, repeat('-updated', 1250));
+
+
+insert into t1 (id, blob_data) values (1, repeat('a', 1024));
+insert into t2 (id, t1_id, copied_blob_data) values (1, 1, repeat('b', 1024));
+
+select * from t2;
+update t1 set id = 2 where id = 1;
+
+select * from t2;
+
+drop table t2;
+drop table t1;
diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index 059cf17e75bf6..5612f25decb9a 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -5166,6 +5166,11 @@ prepare_fk_prelocking_list(THD *thd, Query_tables_list *prelocking_ctx,
         NULL, lock_type, TABLE_LIST::PRELOCK_FK, table_list->belong_to_view,
         op, &prelocking_ctx->query_tables_last, table_list->for_insert_data);
 
+
+    if (fk->delete_method == FK_OPTION_SET_NULL)
+      tl->trg_event_map |= trg2bit(TRG_EVENT_UPDATE);
+
+
 #ifdef WITH_WSREP
     /*
       Append table level shared key for the referenced/foreign table for:
@@ -5239,6 +5244,11 @@ bool DML_prelocking_strategy::handle_table(THD *thd,
 
   if (table_list->trg_event_map && trigger_prelocking_needed)
   {
+    if (prepare_fk_prelocking_list(thd, prelocking_ctx, table_list,
+                                   need_prelocking,
+                                   table_list->trg_event_map))
+      return TRUE;
+
     if (table->triggers)
     {
       *need_prelocking= TRUE;
@@ -5247,11 +5257,6 @@ bool DML_prelocking_strategy::handle_table(THD *thd,
           add_tables_and_routines_for_triggers(thd, prelocking_ctx, table_list))
         return TRUE;
     }
-
-    if (prepare_fk_prelocking_list(thd, prelocking_ctx, table_list,
-                                   need_prelocking,
-                                   table_list->trg_event_map))
-      return TRUE;
   }
   else if (table_list->slave_fk_event_map)
   {
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 1907dbbc06496..5ea6ffe14e6e8 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -13915,3 +13915,94 @@ bool HA_CREATE_INFO::
   }
   return false;
 }
+
+static
+void update_virtual_fields_for_rows(TABLE *table)
+{
+  if (table->vfield) {
+    table->update_virtual_fields(table->file, VCOL_UPDATE_FOR_READ);
+    table->move_fields(table->field, table->record[1], table->record[0]);
+    table->update_virtual_fields(table->file, VCOL_UPDATE_FOR_READ);
+    table->move_fields(table->field, table->record[0], table->record[1]);
+  }
+}
+
+/**
+  Delete a row from the table.
+  The row to be deleted must be present in `table->record[0]`.
+  The handler (`table->file`) must be configured to operate on the data
+  stored in `table->record[0]` (i.e., the effect from calling `ha_rnd_pos` 
+  or `ha_index_read` is required to make a successful call).
+  @param[in,out] table The table object representing the target table.
+  @return error number or 0 */
+int sql_delete_row(TABLE *table)
+{
+  THD *thd= table->in_use;
+  int error= 0;
+  bool trg_skip_row= false;
+  // This ensures that triggers can correctly read virtual field values
+  if (table->vfield) 
+    table->update_virtual_fields(table->file, VCOL_UPDATE_FOR_READ);
+  
+  table->column_bitmaps_set(&table->s->all_set, &table->s->all_set);
+  if (table->triggers &&
+      unlikely(table->triggers->process_triggers(thd, TRG_EVENT_DELETE,
+                                                 TRG_ACTION_BEFORE, FALSE,
+                                                 &trg_skip_row)))
+    return trg_skip_row ? HA_ERR_GENERIC : 0;
+      
+
+  error= table->file->ha_delete_row(table->record[0]);
+  if (error != 0) 
+    return error;
+
+  if (table->triggers &&
+      unlikely(table->triggers->process_triggers(thd, TRG_EVENT_DELETE,
+                                                 TRG_ACTION_AFTER, FALSE,
+                                                 nullptr)))
+    return HA_ERR_GENERIC;
+
+  return 0;
+}
+
+/**
+  Update a row in the table.
+  The old row must be present in `table->record[1]` and the new row in `table->record[0]`.
+  The handler (`table->file`) must be configured to operate on the data
+  stored in `table->record[1]` (i.e., the effect from calling `ha_index_read` 
+  is required to make a successful call).
+  @param[in,out] table The table object representing the target table.
+  @return error number or 0 */
+int sql_update_row(TABLE *table) 
+{
+  THD *thd= current_thd;
+  bool trg_skip_row= false;
+  table->column_bitmaps_set(&table->s->all_set, &table->s->all_set);
+
+  // This ensures that triggers can correctly read virtual field values
+  update_virtual_fields_for_rows(table);
+
+  if (table->triggers && 
+        table->triggers->has_triggers(TRG_EVENT_UPDATE, TRG_ACTION_BEFORE)) 
+  {
+      if (unlikely(table->triggers->process_triggers(thd, TRG_EVENT_UPDATE,
+                                                     TRG_ACTION_BEFORE, TRUE,
+                                                     &trg_skip_row)))
+        return trg_skip_row ? 0 : HA_ERR_GENERIC;
+      // This is necessary for indexes that depend on virtual fields
+      update_virtual_fields_for_rows(table);
+  }
+
+  int error= table->file->ha_update_row(table->record[1], table->record[0]);
+  if (error != 0)
+    return error;
+
+  if (table->triggers &&
+      unlikely(table->triggers->process_triggers(thd, TRG_EVENT_UPDATE,
+                                                 TRG_ACTION_AFTER, TRUE,
+                                                 nullptr)))
+    return HA_ERR_GENERIC;
+
+  return 0;
+}
+
diff --git a/sql/sql_table.h b/sql/sql_table.h
index 4d1d5dff9d582..f4a0fc4809a59 100644
--- a/sql/sql_table.h
+++ b/sql/sql_table.h
@@ -226,4 +226,7 @@ extern MYSQL_PLUGIN_IMPORT const Lex_ident_column primary_key_name;
 
 bool check_engine(THD *, const char *, const char *, HA_CREATE_INFO *);
 
+int sql_delete_row(TABLE *table);
+
+int sql_update_row(TABLE *table);
 #endif /* SQL_TABLE_INCLUDED */
diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index 46f084108153d..d0265af5db8f2 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -2228,6 +2228,91 @@ convert_error_code_to_mysql(
 	}
 }
 
+/**
+  Converts a MariaDB handler error code to an InnoDB error code.
+  An inverse of convert_error_code_to_mysql.
+  @return InnoDB error code
+*/
+static dberr_t
+convert_sql_error_to_dberr(int sql_error)
+{
+  switch (sql_error)
+  {
+  case 0:
+    return DB_SUCCESS;
+
+  case HA_ERR_GENERIC:
+  default:
+    return DB_ERROR;
+
+  case HA_ERR_ABORTED_BY_USER:
+    return DB_INTERRUPTED;
+  case HA_ERR_FK_DEPTH_EXCEEDED:
+    return DB_FOREIGN_EXCEED_MAX_CASCADE;
+  case HA_ERR_NULL_IN_SPATIAL:
+    return DB_CANT_CREATE_GEOMETRY_OBJECT;
+  case HA_ERR_FOUND_DUPP_KEY:
+    return DB_DUPLICATE_KEY;
+  case HA_ERR_TABLE_READONLY:
+    return DB_READ_ONLY;
+  case HA_ERR_FOREIGN_DUPLICATE_KEY:
+    return DB_FOREIGN_DUPLICATE_KEY;
+  case HA_ERR_TABLE_DEF_CHANGED:
+    return DB_MISSING_HISTORY;
+  case HA_ERR_NO_ACTIVE_RECORD:
+    return DB_RECORD_NOT_FOUND;
+  case HA_ERR_LOCK_DEADLOCK:
+    return DB_DEADLOCK;
+  case HA_ERR_RECORD_CHANGED:
+    return DB_RECORD_CHANGED;
+  case HA_ERR_LOCK_WAIT_TIMEOUT:
+    return DB_LOCK_WAIT_TIMEOUT;
+  case HA_ERR_NO_REFERENCED_ROW:
+    return DB_NO_REFERENCED_ROW;
+  case HA_ERR_ROW_IS_REFERENCED:
+    return DB_ROW_IS_REFERENCED;
+  case HA_ERR_CANNOT_ADD_FOREIGN:
+    return DB_CANNOT_ADD_CONSTRAINT;
+  case HA_ERR_CRASHED:
+    return DB_CORRUPTION;
+  case HA_ERR_RECORD_FILE_FULL:
+    return DB_OUT_OF_FILE_SPACE;
+  case HA_ERR_INTERNAL_ERROR:
+    return DB_TEMP_FILE_WRITE_FAIL;
+  case HA_ERR_NO_SUCH_TABLE:
+    return DB_TABLE_NOT_FOUND;
+  case HA_ERR_DECRYPTION_FAILED:
+    return DB_DECRYPTION_FAILED;
+  case HA_ERR_TABLESPACE_MISSING:
+    return DB_TABLESPACE_NOT_FOUND;
+  case HA_ERR_TO_BIG_ROW:
+    return DB_TOO_BIG_RECORD;
+  case HA_ERR_INDEX_COL_TOO_LONG:
+    return DB_TOO_BIG_INDEX_COL;
+  case HA_ERR_LOCK_TABLE_FULL:
+    return DB_LOCK_TABLE_FULL;
+  case HA_FTS_INVALID_DOCID:
+    return DB_FTS_INVALID_DOCID;
+  case HA_ERR_TOO_MANY_CONCURRENT_TRXS:
+    return DB_TOO_MANY_CONCURRENT_TRXS;
+  case HA_ERR_UNSUPPORTED:
+    return DB_UNSUPPORTED;
+  case HA_ERR_INDEX_CORRUPT:
+    return DB_INDEX_CORRUPT;
+  case HA_ERR_UNDO_REC_TOO_BIG:
+    return DB_UNDO_RECORD_TOO_BIG;
+  case HA_ERR_OUT_OF_MEM:
+    return DB_OUT_OF_MEMORY;
+  case HA_ERR_TABLESPACE_EXISTS:
+    return DB_TABLESPACE_EXISTS;
+  case HA_ERR_TABLE_CORRUPT:
+    return DB_TABLE_CORRUPT;
+  case HA_ERR_FTS_TOO_MANY_WORDS_IN_PHRASE:
+    return DB_FTS_TOO_MANY_WORDS_IN_PHRASE;
+  }
+}
+
+
 /*************************************************************//**
 Prints info of a THD object (== user session thread) to the given file. */
 void
@@ -8448,6 +8533,36 @@ ATTRIBUTE_COLD bool wsrep_append_table_key(MYSQL_THD thd,
 }
 #endif /* WITH_WSREP */
 
+int ha_innobase::update_prebuilt_upd_buf()
+{
+  DBUG_ENTER("ha_innobase::update_prebuilt_upd_buf");
+  if (m_upd_buf == NULL)
+  {
+    ut_ad(m_upd_buf_size == 0);
+
+    /*
+      Create a buffer for packing the fields of a record. Why
+      table->reclength did not work here? Obviously, because char
+      fields when packed actually became 1 byte longer, when we also
+      stored the string length as the first byte.
+    */
+
+    m_upd_buf_size = table->s->reclength + table->s->max_key_length
+                     + MAX_REF_PARTS * 3;
+
+    m_upd_buf = reinterpret_cast<uchar*>(
+                    my_malloc(PSI_INSTRUMENT_ME, m_upd_buf_size, MYF(MY_WME)));
+
+    if (m_upd_buf == NULL)
+    {
+      m_upd_buf_size = 0;
+      DBUG_RETURN(HA_ERR_OUT_OF_MEM);
+    }
+  }
+  DBUG_RETURN(0);
+}
+
+
 /**
 Updates a row given as a parameter to a new value. Note that we are given
 whole rows, not just the fields which are updated: this incurs some
@@ -8475,27 +8590,8 @@ ha_innobase::update_row(
 		DBUG_RETURN(err);
 	}
 
-	if (m_upd_buf == NULL) {
-		ut_ad(m_upd_buf_size == 0);
-
-		/* Create a buffer for packing the fields of a record. Why
-		table->reclength did not work here? Obviously, because char
-		fields when packed actually became 1 byte longer, when we also
-		stored the string length as the first byte. */
-
-		m_upd_buf_size = table->s->reclength + table->s->max_key_length
-			+ MAX_REF_PARTS * 3;
-
-		m_upd_buf = reinterpret_cast<uchar*>(
-			my_malloc(PSI_INSTRUMENT_ME,
-                                  m_upd_buf_size,
-				MYF(MY_WME)));
-
-		if (m_upd_buf == NULL) {
-			m_upd_buf_size = 0;
-			DBUG_RETURN(HA_ERR_OUT_OF_MEM);
-		}
-	}
+	if (int ret= update_prebuilt_upd_buf())
+		DBUG_RETURN(ret);
 
 	mariadb_set_stats temp(trx, handler_stats);
 
@@ -21405,3 +21501,107 @@ void alter_stats_rebuild(dict_table_t *table, trx_t *trx) noexcept
                         " table rebuild: %s", ut_strerr(ret));
   DBUG_VOID_RETURN;
 }
+
+
+/**
+Fetch the MariaDB TABLE object corresponding to the InnoDB table
+referenced in the given update node.
+@return Pointer to the TABLE object if found, or nullptr on error. */
+static
+TABLE *find_sql_table_for_update_node(upd_node_t* node) {
+  THD *thd= current_thd;
+  char db_buf[NAME_LEN + 1];
+  char tbl_buf[NAME_LEN + 1];
+  ulint db_buf_len, tbl_buf_len;
+  dict_table_t *table= node->table;
+  if (!table->parse_name(db_buf, tbl_buf, &db_buf_len, &tbl_buf_len)) {
+    return nullptr;
+  }
+
+  return find_fk_open_table(thd, db_buf, db_buf_len, tbl_buf, 
+                                          tbl_buf_len);
+}
+
+
+/**
+  Executes a cascading operation (DELETE or UPDATE) for a foreign key
+  constraint by invoking the corresponding action from sql layer.
+
+  Sets up the MariaDB format table records and cursor.
+
+  @return DB_SUCCESS if OK else error code.
+*/
+dberr_t 
+innodb_do_foreign_cascade(que_thr_t *thr, upd_node_t* node)
+{
+  bool is_delete= (node->is_delete == PLAIN_DELETE);
+
+  TABLE *maria_table= find_sql_table_for_update_node(node);
+
+  ha_innobase *handler= (ha_innobase*)maria_table->file;
+  row_prebuilt_t *prebuilt= handler->get_prebuilt(node->table);
+  btr_pcur_t *pcur= node->pcur;
+  const rec_t* rec= btr_pcur_get_rec(pcur);
+  dict_index_t *clust_index= dict_table_get_first_index(node->table);
+  const rec_offs* offsets= rec_get_offsets(
+          rec, clust_index, nullptr,
+          clust_index->n_core_fields,
+          ULINT_UNDEFINED, &node->heap);
+
+  uint old_rec_idx= is_delete ? 0 : 1;
+  row_sel_store_mysql_rec(maria_table->record[old_rec_idx], prebuilt, rec, NULL,
+                          true, clust_index, offsets);
+
+  if (!is_delete)
+  {
+    /*
+      The following creates the upd_row vector, that can be converted to a
+      mysql row.
+      The memory in row and upd_row is not re-used, following the existing
+      pattern in row_upd_store_row.
+      The memory is then freed in row_upd_store_row, so no memory is leaked.
+     */
+    node->row= row_build(ROW_COPY_DATA, clust_index, rec, offsets, NULL,
+                         NULL, NULL, &node->upd_ext, node->heap);
+
+    node->upd_row= dtuple_copy(node->row, node->heap);
+    row_upd_replace(node->upd_row, &node->upd_ext, clust_index,
+                    node->update, node->heap);
+
+    dtuple_t* entry= row_build_index_entry(node->upd_row, NULL, clust_index,
+                                           node->heap);
+
+    ulint n_ext= dtuple_get_n_ext(node->upd_row);
+
+    ulint size= rec_get_converted_size(clust_index, entry, n_ext);
+    byte *buf= static_cast<byte*>(mem_heap_alloc(node->heap, size));
+
+    rec_t *rec_upd= rec_convert_dtuple_to_rec(buf, clust_index, entry, n_ext);
+    const rec_offs* upd_offsets= rec_get_offsets(
+            rec_upd, clust_index, nullptr,
+            clust_index->n_core_fields,
+            ULINT_UNDEFINED, &node->heap);
+
+    row_sel_store_mysql_rec_keep_blobs(maria_table->record[0], prebuilt,
+                                       rec_upd, NULL, false, clust_index,
+                                       upd_offsets);
+  }
+
+  if (handler->update_prebuilt_upd_buf())
+    return DB_ERROR;
+
+  auto *upd_node= prebuilt->upd_node;
+  auto *upd_graph= prebuilt->upd_graph;
+  prebuilt->upd_node= node;
+  prebuilt->upd_graph= static_cast<que_fork_t*>(que_node_get_parent(thr));
+
+  btr_pcur_copy_stored_position(prebuilt->pcur, pcur);
+  prebuilt->sql_stat_start = FALSE;
+
+  int err = is_delete ? sql_delete_row(maria_table)
+                      : sql_update_row(maria_table);
+
+  prebuilt->upd_node= upd_node;
+  prebuilt->upd_graph= upd_graph;
+  return convert_sql_error_to_dberr(err);
+}
diff --git a/storage/innobase/handler/ha_innodb.h b/storage/innobase/handler/ha_innodb.h
index b6fb571078bea..47cc642268e0b 100644
--- a/storage/innobase/handler/ha_innodb.h
+++ b/storage/innobase/handler/ha_innodb.h
@@ -435,6 +435,12 @@ class ha_innobase final : public handler
 			  const Column_definition& new_field,
 			  const KEY_PART_INFO& old_part,
 			  const KEY_PART_INFO& new_part) const override;
+	row_prebuilt_t *get_prebuilt(const dict_table_t* table) {
+		build_template(true);
+		m_prebuilt->index = dict_table_get_first_index(table);
+		return m_prebuilt;
+	}
+	int update_prebuilt_upd_buf();
 
 	/** Check consistency between .frm indexes and InnoDB indexes
 	Set HA_DUPLICATE_KEY_NOT_IN_ORDER if multiple unique index
@@ -507,14 +513,14 @@ class ha_innobase final : public handler
 	/** Thread handle of the user currently using the handler;
 	this is set in external_lock function */
 	THD*			m_user_thd;
-
+public:
 	/** buffer used in updates */
 	uchar*			m_upd_buf;
 
 	/** the size of upd_buf in bytes */
 	ulint			m_upd_buf_size;
-
-	/** Flags that specify the handler instance (table) capability. */
+protected:
+	/** Flags that specificy the handler instance (table) capability. */
 	Table_flags		m_int_table_flags;
 
 	/** Index into the server's primary key meta-data table->key_info{} */
@@ -934,3 +940,10 @@ ulint dict_table_get_foreign_id(const dict_table_t &table) noexcept;
 @param foreign  foreign key */
 void dict_create_add_foreign_id(ulint *id_nr, const char *name,
                                 dict_foreign_t *foreign) noexcept;
+
+/** An SQL-layer callback for cascade actions
+@param thr Innodb thr
+@param node Innodb update node
+@return DB_SUCCESS or DB_SQL_ERROR
+ */
+dberr_t innodb_do_foreign_cascade(que_thr_t *thr, upd_node_t* node);
diff --git a/storage/innobase/include/row0sel.h b/storage/innobase/include/row0sel.h
index 35e3cbe66315c..e45e71b7b819d 100644
--- a/storage/innobase/include/row0sel.h
+++ b/storage/innobase/include/row0sel.h
@@ -454,3 +454,22 @@ row_sel_field_store_in_mysql_format_func(
 #endif /* UNIV_DEBUG */
         const byte*     data,   /*!< in: data to store */
         ulint           len);    /*!< in: length of the data */
+
+bool row_sel_store_mysql_rec(
+	byte*		mysql_rec,
+	row_prebuilt_t*	prebuilt,
+	const rec_t*	rec,
+	const dtuple_t*	vrow,
+	bool		rec_clust,
+	const dict_index_t* index,
+	const rec_offs*	offsets);
+
+bool
+row_sel_store_mysql_rec_keep_blobs(
+	byte*             mysql_rec,
+	row_prebuilt_t*   prebuilt,
+	const rec_t*      rec,
+	const dtuple_t*   vrow,
+	bool              rec_clust,
+	const dict_index_t* index,
+	const rec_offs*   offsets);
diff --git a/storage/innobase/row/row0mysql.cc b/storage/innobase/row/row0mysql.cc
index 0bbc90cd0f6c2..256144b7abaf6 100644
--- a/storage/innobase/row/row0mysql.cc
+++ b/storage/innobase/row/row0mysql.cc
@@ -65,7 +65,7 @@ Created 9/17/2000 Heikki Tuuri
 #include <algorithm>
 #include <vector>
 #include <thread>
-
+#include "ha_innodb.h"
 
 /** Delay an INSERT, DELETE or UPDATE operation if the purge is lagging. */
 static void row_mysql_delay_if_needed() noexcept
@@ -1660,7 +1660,6 @@ row_update_for_mysql(row_prebuilt_t* prebuilt)
 	for (;;) {
 		thr->run_node = node;
 		thr->prev_node = node;
-		thr->fk_cascade_depth = 0;
 
 		row_upd_step(thr);
 
@@ -1975,7 +1974,11 @@ row_update_cascade_for_mysql(
 		{
 			TABLE *mysql_table = thr->prebuilt->m_mysql_table;
 			thr->prebuilt->m_mysql_table = NULL;
-			row_upd_step(thr);
+
+			dberr_t cascade_error = innodb_do_foreign_cascade(thr,
+									  node);
+			if (UNIV_LIKELY(trx->error_state == DB_SUCCESS))
+				trx->error_state = cascade_error;
 			thr->prebuilt->m_mysql_table = mysql_table;
 		}
 
diff --git a/storage/innobase/row/row0sel.cc b/storage/innobase/row/row0sel.cc
index c063c3b34b810..1bfb6860780c4 100644
--- a/storage/innobase/row/row0sel.cc
+++ b/storage/innobase/row/row0sel.cc
@@ -3117,38 +3117,24 @@ row_sel_store_mysql_field(
 	DBUG_RETURN(TRUE);
 }
 
-/** Convert a row in the Innobase format to a row in the MySQL format.
-Note that the template in prebuilt may advise us to copy only a few
-columns to mysql_rec, other columns are left blank. All columns may not
-be needed in the query.
-@param[out]	mysql_rec	row in the MySQL format
-@param[in]	prebuilt	cursor
-@param[in]	rec		Innobase record in the index
-				which was described in prebuilt's
-				template, or in the clustered index;
-				must be protected by a page latch
-@param[in]	vrow		virtual columns
-@param[in]	rec_clust	whether index must be the clustered index
-@param[in]	index		index of rec
-@param[in]	offsets		array returned by rec_get_offsets(rec)
-@retval true on success
-@retval false if not all columns could be retrieved */
 MY_ATTRIBUTE((warn_unused_result))
-static bool row_sel_store_mysql_rec(
-	byte*		mysql_rec,
-	row_prebuilt_t*	prebuilt,
-	const rec_t*	rec,
-	const dtuple_t*	vrow,
-	bool		rec_clust,
-	const dict_index_t* index,
-	const rec_offs*	offsets)
+static bool
+row_sel_store_mysql_rec_internal(
+    byte*             mysql_rec,
+    row_prebuilt_t*   prebuilt,
+    const rec_t*      rec,
+    const dtuple_t*   vrow,
+    bool              rec_clust,
+    const dict_index_t* index,
+    const rec_offs*   offsets,
+    bool              free_blob)
 {
 	DBUG_ENTER("row_sel_store_mysql_rec");
 
 	ut_ad(rec_clust || index == prebuilt->index);
 	ut_ad(!rec_clust || dict_index_is_clust(index));
 
-	if (UNIV_LIKELY_NULL(prebuilt->blob_heap)) {
+	if (free_blob && UNIV_LIKELY_NULL(prebuilt->blob_heap)) {
 		row_mysql_prebuilt_free_blob_heap(prebuilt);
 	}
 
@@ -3260,6 +3246,65 @@ static bool row_sel_store_mysql_rec(
 	DBUG_RETURN(true);
 }
 
+/** Convert a row in the Innobase format to a row in the MySQL format.
+Note that the template in prebuilt may advise us to copy only a few
+columns to mysql_rec, other columns are left blank. All columns may not
+be needed in the query.
+@param[out]	mysql_rec	row in the MySQL format
+@param[in]	prebuilt	cursor
+@param[in]	rec		Innobase record in the index
+				which was described in prebuilt's
+				template, or in the clustered index;
+				must be protected by a page latch
+@param[in]	vrow		virtual columns
+@param[in]	rec_clust	whether index must be the clustered index
+@param[in]	index		index of rec
+@param[in]	offsets		array returned by rec_get_offsets(rec)
+@retval true on success
+@retval false if not all columns could be retrieved */
+MY_ATTRIBUTE((warn_unused_result))
+bool row_sel_store_mysql_rec(
+	byte*		mysql_rec,
+	row_prebuilt_t*	prebuilt,
+	const rec_t*	rec,
+	const dtuple_t*	vrow,
+	bool		rec_clust,
+	const dict_index_t* index,
+	const rec_offs*	offsets)
+{
+  return row_sel_store_mysql_rec_internal(mysql_rec, prebuilt, rec, vrow,
+    rec_clust, index, offsets, true);
+}
+
+/** Convert a row in the Innobase format to a row in the MySQL format.
+Unlike row_sel_store_mysql_rec, keeps the blobs stored in prebuilt->blob_heap.
+@param[out]	mysql_rec	row in the MySQL format
+@param[in]	prebuilt	cursor
+@param[in]	rec		Innobase record in the index
+                                which was described in prebuilt's
+                                template, or in the clustered index;
+                                must be protected by a page latch
+@param[in]	vrow		virtual columns
+@param[in]	rec_clust	whether index must be the clustered index
+@param[in]	index		index of rec
+@param[in]	offsets		array returned by rec_get_offsets(rec)
+@retval true on success
+@retval false if not all columns could be retrieved */
+MY_ATTRIBUTE((warn_unused_result))
+bool
+row_sel_store_mysql_rec_keep_blobs(
+    byte*             mysql_rec,
+    row_prebuilt_t*   prebuilt,
+    const rec_t*      rec,
+    const dtuple_t*   vrow,
+    bool              rec_clust,
+    const dict_index_t* index,
+    const rec_offs*   offsets)
+{
+    return row_sel_store_mysql_rec_internal(mysql_rec, prebuilt, rec, vrow,
+                                              rec_clust, index, offsets, false);
+}
+
 static void row_sel_reset_old_vers_heap(row_prebuilt_t *prebuilt)
 {
   if (prebuilt->old_vers_heap)
diff --git a/storage/innobase/ut/ut0ut.cc b/storage/innobase/ut/ut0ut.cc
index b5799689d979e..e9757ca0dc223 100644
--- a/storage/innobase/ut/ut0ut.cc
+++ b/storage/innobase/ut/ut0ut.cc
@@ -418,7 +418,6 @@ ut_strerr(
 		return ("File system does not support punch hole (trim) operation.");
 	case DB_PAGE_CORRUPTED:
 		return("Page read from tablespace is corrupted.");
-
 	/* do not add default: in order to produce a warning if new code
 	is added to the enum but not added here */
 	}

From 26a72c46c0bf1e836c214924252bf33a076bdb65 Mon Sep 17 00:00:00 2001
From: Nikita Malyavin <nikitamalyavin@gmail.com>
Date: Tue, 10 Feb 2026 02:03:16 +0100
Subject: [PATCH 2/6] MDEV-12302 Add SQL errors handling

Bypass the errors from sql layer, through innodb back to sql layer.
New handler error: HA_ERR_CASCADE_SQL
New innodb error: DB_SQL_ERROR

This error is not visible to user and serves only for correct error
transport. The real error code is expected to be stored in
thd->m_stmt_da, that is, already reported

This is a fixup commit.
Original author: Simoffsky <maks-kirsanov26@mail.ru>
---
 include/my_base.h                             |  3 +-
 include/my_handler_errors.h                   |  3 +-
 .../suite/innodb/r/trigger_cascade.result     | 26 +++++++++++++++
 .../suite/innodb/t/trigger_cascade.test       | 33 +++++++++++++++++++
 sql/handler.cc                                |  4 +++
 sql/sql_table.cc                              |  8 ++---
 storage/innobase/handler/ha_innodb.cc         | 14 +++++---
 storage/innobase/include/db0err.h             |  2 ++
 storage/innobase/include/trx0trx.h            |  8 +++++
 storage/innobase/row/row0mysql.cc             |  1 +
 storage/innobase/ut/ut0ut.cc                  |  2 ++
 11 files changed, 94 insertions(+), 10 deletions(-)

diff --git a/include/my_base.h b/include/my_base.h
index 8fdd1397ff09d..0a85444de31fb 100644
--- a/include/my_base.h
+++ b/include/my_base.h
@@ -557,7 +557,8 @@ enum ha_base_keytype {
 #define HA_ERR_ROLLBACK           200  /* Automatic rollback done */
 #define HA_ERR_LOCAL_TMP_SPACE_FULL   201
 #define HA_ERR_GLOBAL_TMP_SPACE_FULL  202
-#define HA_ERR_LAST               202  /* Copy of last error nr * */
+#define HA_ERR_CASCADE_SQL        203 /* Error happened in cascade sql action */
+#define HA_ERR_LAST               203  /* Copy of last error nr * */
 
 /* Number of different errors */
 #define HA_ERR_ERRORS            (HA_ERR_LAST - HA_ERR_FIRST + 1)
diff --git a/include/my_handler_errors.h b/include/my_handler_errors.h
index c98e8cbafd739..3d4f959ffe934 100644
--- a/include/my_handler_errors.h
+++ b/include/my_handler_errors.h
@@ -114,7 +114,8 @@ static const char *handler_error_messages[]=
   "Transaction was aborted",
   /* HA_ERR_LOCAL_TMP_SPACE_FULL=201 */
   "Local temporary space limit reached",
-  "Global temporary space limit reached"
+  "Global temporary space limit reached",
+  "Error in cascade SQL action",
 };
 
 #endif /* MYSYS_MY_HANDLER_ERRORS_INCLUDED */
diff --git a/mysql-test/suite/innodb/r/trigger_cascade.result b/mysql-test/suite/innodb/r/trigger_cascade.result
index a0f7e8ac4b0f6..84c61250eb2b9 100644
--- a/mysql-test/suite/innodb/r/trigger_cascade.result
+++ b/mysql-test/suite/innodb/r/trigger_cascade.result
@@ -380,3 +380,29 @@ id	t1_id	copied_blob_data
 1	2	bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated-updated
 drop table t2;
 drop table t1;
+#
+# With blobs error too long
+#
+create table t1 (
+id int primary key,
+blob_data blob
+) engine=innodb;
+create table t2 (
+id int primary key,
+t1_id int,
+copied_blob_data blob,
+foreign key (t1_id) references t1(id) on delete cascade on update cascade
+) engine=innodb;
+create trigger tr_t2_before_update
+before update on t2
+for each row
+set new.copied_blob_data = concat(old.copied_blob_data, repeat('-updated', 12500));
+insert into t1 (id, blob_data) values (1, repeat('a', 1024));
+insert into t2 (id, t1_id, copied_blob_data) values (1, 1, repeat('b', 1024));
+select * from t2;
+id	t1_id	copied_blob_data
+1	1	bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+update t1 set id = 2 where id = 1;
+ERROR 22001: Data too long for column 'copied_blob_data' at row 0
+drop table t2;
+drop table t1;
diff --git a/mysql-test/suite/innodb/t/trigger_cascade.test b/mysql-test/suite/innodb/t/trigger_cascade.test
index 3fba13afc2259..ad5e8de6778b0 100644
--- a/mysql-test/suite/innodb/t/trigger_cascade.test
+++ b/mysql-test/suite/innodb/t/trigger_cascade.test
@@ -416,3 +416,36 @@ select * from t2;
 
 drop table t2;
 drop table t1;
+
+--echo #
+--echo # With blobs error too long
+--echo #
+
+create table t1 (
+    id int primary key,
+    blob_data blob
+) engine=innodb;
+
+create table t2 (
+    id int primary key,
+    t1_id int,
+    copied_blob_data blob,
+    foreign key (t1_id) references t1(id) on delete cascade on update cascade
+) engine=innodb;
+
+
+create trigger tr_t2_before_update
+before update on t2
+for each row
+set new.copied_blob_data = concat(old.copied_blob_data, repeat('-updated', 12500));
+
+
+insert into t1 (id, blob_data) values (1, repeat('a', 1024));
+insert into t2 (id, t1_id, copied_blob_data) values (1, 1, repeat('b', 1024));
+
+select * from t2;
+--error ER_DATA_TOO_LONG
+update t1 set id = 2 where id = 1;
+
+drop table t2;
+drop table t1;
diff --git a/sql/handler.cc b/sql/handler.cc
index 65af1a4b095bd..bb57f12e66bfd 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -5269,6 +5269,10 @@ void handler::print_error(int error, myf errflag)
     SET_FATAL_ERROR;
     textno= ER_ROLLBACK_ONLY;
     break;
+  case HA_ERR_CASCADE_SQL:
+    // Cascade error should be already reported.
+    DBUG_ASSERT(table->in_use->get_stmt_da()->is_error());
+    DBUG_VOID_RETURN;
   default:
     {
       /* The error was "unknown" to this function.
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 5ea6ffe14e6e8..ce608e361695b 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -13949,7 +13949,7 @@ int sql_delete_row(TABLE *table)
       unlikely(table->triggers->process_triggers(thd, TRG_EVENT_DELETE,
                                                  TRG_ACTION_BEFORE, FALSE,
                                                  &trg_skip_row)))
-    return trg_skip_row ? HA_ERR_GENERIC : 0;
+    return trg_skip_row ? HA_ERR_CASCADE_SQL : 0;
       
 
   error= table->file->ha_delete_row(table->record[0]);
@@ -13960,7 +13960,7 @@ int sql_delete_row(TABLE *table)
       unlikely(table->triggers->process_triggers(thd, TRG_EVENT_DELETE,
                                                  TRG_ACTION_AFTER, FALSE,
                                                  nullptr)))
-    return HA_ERR_GENERIC;
+    return HA_ERR_CASCADE_SQL;
 
   return 0;
 }
@@ -13988,7 +13988,7 @@ int sql_update_row(TABLE *table)
       if (unlikely(table->triggers->process_triggers(thd, TRG_EVENT_UPDATE,
                                                      TRG_ACTION_BEFORE, TRUE,
                                                      &trg_skip_row)))
-        return trg_skip_row ? 0 : HA_ERR_GENERIC;
+        return trg_skip_row ? 0 : HA_ERR_CASCADE_SQL;
       // This is necessary for indexes that depend on virtual fields
       update_virtual_fields_for_rows(table);
   }
@@ -14001,7 +14001,7 @@ int sql_update_row(TABLE *table)
       unlikely(table->triggers->process_triggers(thd, TRG_EVENT_UPDATE,
                                                  TRG_ACTION_AFTER, TRUE,
                                                  nullptr)))
-    return HA_ERR_GENERIC;
+    return HA_ERR_CASCADE_SQL;
 
   return 0;
 }
diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index d0265af5db8f2..967cce76c2a2c 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -2223,6 +2223,8 @@ convert_error_code_to_mysql(
 		return(HA_ERR_TABLE_CORRUPT);
 	case DB_FTS_TOO_MANY_WORDS_IN_PHRASE:
 		return(HA_ERR_FTS_TOO_MANY_WORDS_IN_PHRASE);
+	case DB_SQL_ERROR:
+		return(HA_ERR_CASCADE_SQL);
 	case DB_COMPUTE_VALUE_FAILED:
 		return(HA_ERR_GENERIC); // impossible
 	}
@@ -2234,12 +2236,16 @@ convert_error_code_to_mysql(
   @return InnoDB error code
 */
 static dberr_t
-convert_sql_error_to_dberr(int sql_error)
+convert_sql_error_to_dberr(THD *thd, que_thr_t *thr, int sql_error)
 {
   switch (sql_error)
   {
   case 0:
     return DB_SUCCESS;
+  case HA_ERR_CASCADE_SQL:
+    // this error should be accessible with thd->get_stmt_da()->sql_errno()
+    ut_ad(thd->get_stmt_da()->is_error());
+    return DB_SQL_ERROR;
 
   case HA_ERR_GENERIC:
   default:
@@ -21503,8 +21509,8 @@ void alter_stats_rebuild(dict_table_t *table, trx_t *trx) noexcept
 }
 
 
-/**
-Fetch the MariaDB TABLE object corresponding to the InnoDB table
+/********************************************************************//**
+Fetches the MySQL TABLE object corresponding to the InnoDB table
 referenced in the given update node.
 @return Pointer to the TABLE object if found, or nullptr on error. */
 static
@@ -21603,5 +21609,5 @@ innodb_do_foreign_cascade(que_thr_t *thr, upd_node_t* node)
 
   prebuilt->upd_node= upd_node;
   prebuilt->upd_graph= upd_graph;
-  return convert_sql_error_to_dberr(err);
+  return convert_sql_error_to_dberr(maria_table->in_use, thr, err);
 }
diff --git a/storage/innobase/include/db0err.h b/storage/innobase/include/db0err.h
index 642a3d2dbe05a..4f728e29e0a19 100644
--- a/storage/innobase/include/db0err.h
+++ b/storage/innobase/include/db0err.h
@@ -165,6 +165,8 @@ enum dberr_t {
 	DB_END_OF_INDEX,
 	DB_NOT_FOUND,			/*!< Generic error code for "Not found"
 					type of errors */
+	DB_SQL_ERROR,			/*!< An error happened inside sql-layer
+					callback */
 };
 
 #endif
diff --git a/storage/innobase/include/trx0trx.h b/storage/innobase/include/trx0trx.h
index 2063f1179dabc..852f08e0b50dd 100644
--- a/storage/innobase/include/trx0trx.h
+++ b/storage/innobase/include/trx0trx.h
@@ -889,6 +889,14 @@ struct trx_t : ilist_node<>
   lock_wait(). That is protected by lock_sys.wait_mutex and lock.wait_lock. */
   dberr_t error_state;
 
+  /*
+  When handling cascade operations (e.g. foreign key updates/deletes), 
+  nested SQL operations may generate errors that are already stored 
+  in sql_error. In these scenarios, we preserve the original error 
+  state and skip redundant error conversion.
+  */
+  int sql_error;
+
 	const dict_index_t*error_info;	/*!< if the error number indicates a
 					duplicate key error, a pointer to
 					the problematic index is stored here */
diff --git a/storage/innobase/row/row0mysql.cc b/storage/innobase/row/row0mysql.cc
index 256144b7abaf6..63c3f0d612c08 100644
--- a/storage/innobase/row/row0mysql.cc
+++ b/storage/innobase/row/row0mysql.cc
@@ -672,6 +672,7 @@ row_mysql_handle_errors(
 	case DB_TABLE_NOT_FOUND:
 	case DB_DECRYPTION_FAILED:
 	case DB_COMPUTE_VALUE_FAILED:
+	case DB_SQL_ERROR:
 	rollback_to_savept:
 		DBUG_EXECUTE_IF("row_mysql_crash_if_error", {
 					log_buffer_flush_to_disk();
diff --git a/storage/innobase/ut/ut0ut.cc b/storage/innobase/ut/ut0ut.cc
index e9757ca0dc223..3b11001b6fdd7 100644
--- a/storage/innobase/ut/ut0ut.cc
+++ b/storage/innobase/ut/ut0ut.cc
@@ -418,6 +418,8 @@ ut_strerr(
 		return ("File system does not support punch hole (trim) operation.");
 	case DB_PAGE_CORRUPTED:
 		return("Page read from tablespace is corrupted.");
+	case DB_SQL_ERROR:
+		return("Error happened at sql layer.");
 	/* do not add default: in order to produce a warning if new code
 	is added to the enum but not added here */
 	}

From 767ba4048ca14550c8342397a37da1f34b71c3a9 Mon Sep 17 00:00:00 2001
From: Nikita Malyavin <nikitamalyavin@gmail.com>
Date: Thu, 12 Feb 2026 17:36:31 +0100
Subject: [PATCH 3/6] MDEV-12302 Refactor fk cascade depth check

* Move inc and dec for fk_cascade_depth close to each other, in a
symmetrical manner, wrapping the recursive call.

* Remove conputation-heavy node traversal with
row_ins_cascade_n_ancestors for each cascade call,
resulting in O(depth^2) total passes. It should be enough to do that
only as an assertion. Historically, there could be more than one thr,
joined in chains (but then we'd better pass over a chain of thr). Now a
single thr is used for cascade call, so no need in any graph traversal.

* Fix max cascade error handling -- now HA_ERR_FK_DEPTH_EXCEEDED is
returned, as implied.
---
 include/handler_ername.h                     |  1 +
 mysql-test/suite/innodb/r/foreign_key.result |  8 +++---
 mysql-test/suite/innodb/t/foreign_key.test   |  2 +-
 mysql-test/suite/innodb/t/innodb.test        |  2 +-
 storage/innobase/handler/ha_innodb.cc        | 27 +++++++++++---------
 storage/innobase/row/row0ins.cc              | 18 ++++++-------
 storage/innobase/row/row0mysql.cc            | 12 ---------
 7 files changed, 31 insertions(+), 39 deletions(-)

diff --git a/include/handler_ername.h b/include/handler_ername.h
index 74a07c8707826..4ba0b07a5f498 100644
--- a/include/handler_ername.h
+++ b/include/handler_ername.h
@@ -78,6 +78,7 @@
 { "HA_ERR_ABORTED_BY_USER", HA_ERR_ABORTED_BY_USER, "" },
 { "HA_ERR_DISK_FULL", HA_ERR_DISK_FULL, "" },
 { "HA_ERR_INCOMPATIBLE_DEFINITION", HA_ERR_INCOMPATIBLE_DEFINITION, "" },
+{ "HA_ERR_FK_DEPTH_EXCEEDED", HA_ERR_FK_DEPTH_EXCEEDED, "" },
 { "HA_ERR_COMMIT_ERROR", HA_ERR_COMMIT_ERROR, "" },
 { "HA_ERR_PARTITION_LIST", HA_ERR_PARTITION_LIST, ""},
 { "HA_ERR_NO_ENCRYPTION", HA_ERR_NO_ENCRYPTION, ""},
diff --git a/mysql-test/suite/innodb/r/foreign_key.result b/mysql-test/suite/innodb/r/foreign_key.result
index d98da3242f856..5b7d6d7c19b0a 100644
--- a/mysql-test/suite/innodb/r/foreign_key.result
+++ b/mysql-test/suite/innodb/r/foreign_key.result
@@ -707,9 +707,9 @@ connection default;
 DELETE IGNORE FROM t1 WHERE b = 1;
 Warnings:
 Warning	152	InnoDB: Cannot delete/update rows with cascading foreign key constraints that exceed max depth of 15. Please drop extra constraints and try again
-Warning	1296	Got error 193 '`test`.`t1`, CONSTRAINT `1` FOREIGN KEY (`a`) REFERENCES `t1` (`b`) ON DELETE CASCADE' from InnoDB
+Warning	1030	Got error 193 "Foreign key cascade delete/update exceeds max depth" from storage engine InnoDB
 Warning	152	InnoDB: Cannot delete/update rows with cascading foreign key constraints that exceed max depth of 15. Please drop extra constraints and try again
-Warning	1296	Got error 193 '`test`.`t1`, CONSTRAINT `1` FOREIGN KEY (`a`) REFERENCES `t1` (`b`) ON DELETE CASCADE' from InnoDB
+Warning	1030	Got error 193 "Foreign key cascade delete/update exceeds max depth" from storage engine InnoDB
 SELECT a FROM t1 FORCE INDEX(a);
 a
 0
@@ -872,11 +872,11 @@ INSERT INTO t1 (a,b) VALUES
 (0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
 (0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,1),(1,0);
 DELETE FROM t1 WHERE b = 1;
-ERROR HY000: Got error 193 '`test`.`t1`, CONSTRAINT `1` FOREIGN KEY (`a`) REFERENCES `t1` (`b`) ON DELETE CASCADE' from InnoDB
+ERROR HY000: Got error 193 "Foreign key cascade delete/update exceeds max depth" from storage engine InnoDB
 SHOW WARNINGS;
 Level	Code	Message
 Warning	152	InnoDB: Cannot delete/update rows with cascading foreign key constraints that exceed max depth of 15. Please drop extra constraints and try again
-Error	1296	Got error 193 '`test`.`t1`, CONSTRAINT `1` FOREIGN KEY (`a`) REFERENCES `t1` (`b`) ON DELETE CASCADE' from InnoDB
+Error	1030	Got error 193 "Foreign key cascade delete/update exceeds max depth" from storage engine InnoDB
 DROP TABLE t1;
 FOUND 1 /InnoDB: Cannot delete/update rows with cascading foreign key constraints that exceed max depth of 15.*/ in mysqld.1.err
 # End of 10.2 tests
diff --git a/mysql-test/suite/innodb/t/foreign_key.test b/mysql-test/suite/innodb/t/foreign_key.test
index 6ce3936369036..4b9f83fc2c28e 100644
--- a/mysql-test/suite/innodb/t/foreign_key.test
+++ b/mysql-test/suite/innodb/t/foreign_key.test
@@ -878,7 +878,7 @@ INSERT INTO t1 (a,b) VALUES
 (0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,0),
 (0,0),(0,0),(0,0),(0,0),(0,0),(0,0),(0,1),(1,0);
 
---error ER_GET_ERRMSG
+--error ER_GET_ERRNO
 DELETE FROM t1 WHERE b = 1;
 SHOW WARNINGS;
 DROP TABLE t1;
diff --git a/mysql-test/suite/innodb/t/innodb.test b/mysql-test/suite/innodb/t/innodb.test
index ca0eb06d6133a..112ab529f98b3 100644
--- a/mysql-test/suite/innodb/t/innodb.test
+++ b/mysql-test/suite/innodb/t/innodb.test
@@ -1064,7 +1064,7 @@ create table t1(
 	foreign key(pid) references t1(id) on delete cascade) engine=innodb;
 insert into t1 values(0,0),(1,0),(2,1),(3,2),(4,3),(5,4),(6,5),(7,6),
 (8,7),(9,8),(10,9),(11,10),(12,11),(13,12),(14,13),(15,14);
---error ER_GET_ERRMSG,ER_ROW_IS_REFERENCED_2
+--error ER_GET_ERRNO,ER_ROW_IS_REFERENCED_2
 delete from t1 where id=0;
 delete from t1 where id=15;
 delete from t1 where id=0;
diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index 967cce76c2a2c..2b76b27be8df4 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -2050,15 +2050,6 @@ convert_error_code_to_mysql(
 		return(HA_ERR_ABORTED_BY_USER);
 
 	case DB_FOREIGN_EXCEED_MAX_CASCADE:
-		ut_ad(thd);
-		push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
-				    HA_ERR_ROW_IS_REFERENCED,
-				    "InnoDB: Cannot delete/update "
-				    "rows with cascading foreign key "
-				    "constraints that exceed max "
-				    "depth of %d. Please "
-				    "drop extra constraints and try "
-				    "again", FK_MAX_CASCADE_DEL);
 		return(HA_ERR_FK_DEPTH_EXCEEDED);
 
 	case DB_CANT_CREATE_GEOMETRY_OBJECT:
@@ -2254,6 +2245,15 @@ convert_sql_error_to_dberr(THD *thd, que_thr_t *thr, int sql_error)
   case HA_ERR_ABORTED_BY_USER:
     return DB_INTERRUPTED;
   case HA_ERR_FK_DEPTH_EXCEEDED:
+    if (thr->fk_cascade_depth == 0)
+      push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
+                          HA_ERR_ROW_IS_REFERENCED,
+                          "InnoDB: Cannot delete/update "
+                          "rows with cascading foreign key "
+                          "constraints that exceed max "
+                          "depth of %d. Please "
+                          "drop extra constraints and try "
+                          "again", FK_MAX_CASCADE_DEL);
     return DB_FOREIGN_EXCEED_MAX_CASCADE;
   case HA_ERR_NULL_IN_SPATIAL:
     return DB_CANT_CREATE_GEOMETRY_OBJECT;
@@ -21544,6 +21544,7 @@ innodb_do_foreign_cascade(que_thr_t *thr, upd_node_t* node)
 
   TABLE *maria_table= find_sql_table_for_update_node(node);
 
+  THD *thd= maria_table->in_use;
   ha_innobase *handler= (ha_innobase*)maria_table->file;
   row_prebuilt_t *prebuilt= handler->get_prebuilt(node->table);
   btr_pcur_t *pcur= node->pcur;
@@ -21594,7 +21595,7 @@ innodb_do_foreign_cascade(que_thr_t *thr, upd_node_t* node)
   }
 
   if (handler->update_prebuilt_upd_buf())
-    return DB_ERROR;
+    return DB_OUT_OF_MEMORY;
 
   auto *upd_node= prebuilt->upd_node;
   auto *upd_graph= prebuilt->upd_graph;
@@ -21604,8 +21605,10 @@ innodb_do_foreign_cascade(que_thr_t *thr, upd_node_t* node)
   btr_pcur_copy_stored_position(prebuilt->pcur, pcur);
   prebuilt->sql_stat_start = FALSE;
 
-  int err = is_delete ? sql_delete_row(maria_table)
-                      : sql_update_row(maria_table);
+  ++thr->fk_cascade_depth;
+  int err= is_delete ? sql_delete_row(maria_table)
+                     : sql_update_row(maria_table);
+  --thr->fk_cascade_depth;
 
   prebuilt->upd_node= upd_node;
   prebuilt->upd_graph= upd_graph;
diff --git a/storage/innobase/row/row0ins.cc b/storage/innobase/row/row0ins.cc
index 87d02da38e5a7..9166223c74f97 100644
--- a/storage/innobase/row/row0ins.cc
+++ b/storage/innobase/row/row0ins.cc
@@ -1106,16 +1106,16 @@ row_ins_foreign_check_on_constraint(
 			goto nonstandard_exit_func;
 		}
 	}
-
-	if (row_ins_cascade_n_ancestors(cascade) >= FK_MAX_CASCADE_DEL) {
-		err = DB_FOREIGN_EXCEED_MAX_CASCADE;
-
-		row_ins_foreign_report_err(
-			"Trying a too deep cascaded delete or update\n",
-			thr, foreign, btr_pcur_get_rec(pcur), entry);
-
-		goto nonstandard_exit_func;
+	/* Check fk_cascade_depth to limit the recursive call depth on
+	a single update/delete that affects multiple tables chained
+	together with foreign key relations.
+	fk_cascade_depth increments later, so we have to add 1 here. */
+	if (UNIV_UNLIKELY(thr->fk_cascade_depth + 1 >= FK_MAX_CASCADE_DEL))
+	{
+	  err= DB_FOREIGN_EXCEED_MAX_CASCADE;
+	  goto nonstandard_exit_func;
 	}
+	ut_ad(row_ins_cascade_n_ancestors(cascade) < FK_MAX_CASCADE_DEL);
 
 	index = pcur->index();
 
diff --git a/storage/innobase/row/row0mysql.cc b/storage/innobase/row/row0mysql.cc
index 63c3f0d612c08..7bb3c9eadcabf 100644
--- a/storage/innobase/row/row0mysql.cc
+++ b/storage/innobase/row/row0mysql.cc
@@ -1919,7 +1919,6 @@ static dberr_t row_update_vers_insert(que_thr_t* thr, upd_node_t* node)
 			/* fall through */
 		default:
 			/* Other errors are handled for the parent node. */
-			thr->fk_cascade_depth = 0;
 			goto exit;
 
 		case DB_SUCCESS:
@@ -1945,14 +1944,6 @@ row_update_cascade_for_mysql(
                                 or set null operation */
         dict_table_t*   table)  /*!< in: table where we do the operation */
 {
-        /* Increment fk_cascade_depth to record the recursive call depth on
-        a single update/delete that affects multiple tables chained
-        together with foreign key relations. */
-
-        if (++thr->fk_cascade_depth > FK_MAX_CASCADE_DEL) {
-                return(DB_FOREIGN_EXCEED_MAX_CASCADE);
-        }
-
 	trx_t* trx = thr_get_trx(thr);
 
 	if (table->versioned()) {
@@ -1991,12 +1982,9 @@ row_update_cascade_for_mysql(
 
 			/* fall through */
 		default:
-			/* Other errors are handled for the parent node. */
-			thr->fk_cascade_depth = 0;
 			return trx->error_state;
 
 		case DB_SUCCESS:
-			thr->fk_cascade_depth = 0;
 			bool stats;
 
 			if (node->is_delete == PLAIN_DELETE) {

From c0717436c9357dd4784fc0454790f0b91cba6641 Mon Sep 17 00:00:00 2001
From: Nikita Malyavin <nikitamalyavin@gmail.com>
Date: Thu, 12 Feb 2026 22:58:44 +0100
Subject: [PATCH 4/6] MDEV-12302 Move fk cascade depth control to THD

que_thr_t is not bypassed in between trigger calls, that is the count
starts from 0 each time in the trigger.

This means that an effective depth restriction is a multiplication of
FK_MAX_CASCADE_DEL and max_sp_recursion_depth.

Moving the control to THD changes this to addition.

Now the depth limit is: FK_MAX_CASCADE_DEL + max_sp_recursion_depth
---
 .../suite/innodb/r/trigger_cascade.result     | 56 +++++++++++++++++++
 .../suite/innodb/t/trigger_cascade.test       | 29 ++++++++++
 sql/sql_class.cc                              |  1 +
 sql/sql_class.h                               |  1 +
 storage/innobase/handler/ha_innodb.cc         |  6 +-
 storage/innobase/include/que0que.h            |  3 -
 storage/innobase/row/row0ins.cc               |  3 +-
 7 files changed, 92 insertions(+), 7 deletions(-)

diff --git a/mysql-test/suite/innodb/r/trigger_cascade.result b/mysql-test/suite/innodb/r/trigger_cascade.result
index 84c61250eb2b9..92c47d9a709e6 100644
--- a/mysql-test/suite/innodb/r/trigger_cascade.result
+++ b/mysql-test/suite/innodb/r/trigger_cascade.result
@@ -406,3 +406,59 @@ update t1 set id = 2 where id = 1;
 ERROR 22001: Data too long for column 'copied_blob_data' at row 0
 drop table t2;
 drop table t1;
+# max depth is incrementally limited for cascade actions inside triggers
+create table t2(
+id int primary key,
+pid int,
+index(pid),
+foreign key(pid) references t2(id) on delete cascade) engine=innodb;
+insert into t2 values(0,0),(1,0),(2,1),(3,2),(4,3),(5,4),(6,5),(7,6),
+(8,7),(9,8),(10,9),(11,10),(12,11),(13,12),(14,13);
+create table t1(
+id int primary key,
+pid int,
+index(pid),
+foreign key(pid) references t1(id) on delete cascade) engine=innodb;
+create trigger trg before delete on t1 for each row
+delete from t2 where id = 0 and old.id=14;
+insert into t1 values(0,0),(1,0),(2,1),(3,2),(4,3),(5,4),(6,5),(7,6),
+(8,7),(9,8),(10,9),(11,10),(12,11),(13,12),(14,13);
+delete from t1 where id=0;
+ERROR HY000: Got error 193 "Foreign key cascade delete/update exceeds max depth" from storage engine InnoDB
+select * from t2;
+id	pid
+0	0
+1	0
+2	1
+3	2
+4	3
+5	4
+6	5
+7	6
+8	7
+9	8
+10	9
+11	10
+12	11
+13	12
+14	13
+select * from t1;
+id	pid
+0	0
+1	0
+2	1
+3	2
+4	3
+5	4
+6	5
+7	6
+8	7
+9	8
+10	9
+11	10
+12	11
+13	12
+14	13
+drop table t1;
+drop table t2;
+call mtr.add_suppression("InnoDB: Cannot delete/update rows with cascading foreign key constraints that exceed max depth of 15\\.");
diff --git a/mysql-test/suite/innodb/t/trigger_cascade.test b/mysql-test/suite/innodb/t/trigger_cascade.test
index ad5e8de6778b0..2c984cdc64de4 100644
--- a/mysql-test/suite/innodb/t/trigger_cascade.test
+++ b/mysql-test/suite/innodb/t/trigger_cascade.test
@@ -449,3 +449,32 @@ update t1 set id = 2 where id = 1;
 
 drop table t2;
 drop table t1;
+
+--echo # max depth is incrementally limited for cascade actions inside triggers
+
+create table t2(
+  id int primary key,
+  pid int,
+  index(pid),
+  foreign key(pid) references t2(id) on delete cascade) engine=innodb;
+insert into t2 values(0,0),(1,0),(2,1),(3,2),(4,3),(5,4),(6,5),(7,6),
+                     (8,7),(9,8),(10,9),(11,10),(12,11),(13,12),(14,13);
+
+create table t1(
+  id int primary key,
+  pid int,
+  index(pid),
+  foreign key(pid) references t1(id) on delete cascade) engine=innodb;
+
+create trigger trg before delete on t1 for each row
+  delete from t2 where id = 0 and old.id=14;
+
+insert into t1 values(0,0),(1,0),(2,1),(3,2),(4,3),(5,4),(6,5),(7,6),
+                     (8,7),(9,8),(10,9),(11,10),(12,11),(13,12),(14,13);
+--error ER_GET_ERRNO
+delete from t1 where id=0;
+select * from t2;
+select * from t1;
+drop table t1;
+drop table t2;
+call mtr.add_suppression("InnoDB: Cannot delete/update rows with cascading foreign key constraints that exceed max depth of 15\\.");
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 42723fb6caf62..035d9cb69c559 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -746,6 +746,7 @@ THD::THD(my_thread_id id, bool is_wsrep_applier)
    derived_tables_processing(FALSE),
    waiting_on_group_commit(FALSE), has_waiter(FALSE),
    last_sql_command(SQLCOM_END), spcont(NULL),
+   fk_cascade_depth(0),
    m_parser_state(NULL),
 #ifndef EMBEDDED_LIBRARY
    audit_plugin_version(-1),
diff --git a/sql/sql_class.h b/sql/sql_class.h
index f8f9290405ba3..5e03d24eff022 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -4349,6 +4349,7 @@ class THD: public THD_count, /* this must be first */
 
   /** number of name_const() substitutions, see sp_head.cc:subst_spvars() */
   uint       query_name_consts;
+  uint       fk_cascade_depth;
 
   NET*       slave_net;			// network connection from slave -> m.
 
diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index 2b76b27be8df4..3f49914f67b43 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -2245,7 +2245,7 @@ convert_sql_error_to_dberr(THD *thd, que_thr_t *thr, int sql_error)
   case HA_ERR_ABORTED_BY_USER:
     return DB_INTERRUPTED;
   case HA_ERR_FK_DEPTH_EXCEEDED:
-    if (thr->fk_cascade_depth == 0)
+    if (thd->fk_cascade_depth == 0)
       push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
                           HA_ERR_ROW_IS_REFERENCED,
                           "InnoDB: Cannot delete/update "
@@ -21605,10 +21605,10 @@ innodb_do_foreign_cascade(que_thr_t *thr, upd_node_t* node)
   btr_pcur_copy_stored_position(prebuilt->pcur, pcur);
   prebuilt->sql_stat_start = FALSE;
 
-  ++thr->fk_cascade_depth;
+  ++thd->fk_cascade_depth;
   int err= is_delete ? sql_delete_row(maria_table)
                      : sql_update_row(maria_table);
-  --thr->fk_cascade_depth;
+  --thd->fk_cascade_depth;
 
   prebuilt->upd_node= upd_node;
   prebuilt->upd_graph= upd_graph;
diff --git a/storage/innobase/include/que0que.h b/storage/innobase/include/que0que.h
index 6485e21e7fc5a..8d9a6fc2bd4e8 100644
--- a/storage/innobase/include/que0que.h
+++ b/storage/innobase/include/que0que.h
@@ -255,9 +255,6 @@ struct que_thr_t{
 	UT_LIST_NODE_T(que_thr_t)
 			queue;		/*!< list of runnable thread nodes in
 					the server task queue */
-	ulint		fk_cascade_depth; /*!< maximum cascading call depth
-					supported for foreign key constraint
-					related delete/updates */
 	row_prebuilt_t*	prebuilt;	/*!< prebuilt structure processed by
 					the query thread */
 };
diff --git a/storage/innobase/row/row0ins.cc b/storage/innobase/row/row0ins.cc
index 9166223c74f97..03ab40b985474 100644
--- a/storage/innobase/row/row0ins.cc
+++ b/storage/innobase/row/row0ins.cc
@@ -1110,7 +1110,8 @@ row_ins_foreign_check_on_constraint(
 	a single update/delete that affects multiple tables chained
 	together with foreign key relations.
 	fk_cascade_depth increments later, so we have to add 1 here. */
-	if (UNIV_UNLIKELY(thr->fk_cascade_depth + 1 >= FK_MAX_CASCADE_DEL))
+	if (UNIV_UNLIKELY(trx->mysql_thd->fk_cascade_depth + 1 >=
+							FK_MAX_CASCADE_DEL))
 	{
 	  err= DB_FOREIGN_EXCEED_MAX_CASCADE;
 	  goto nonstandard_exit_func;

From 9776d1e11d53c3b54b516feae58214fee8277e18 Mon Sep 17 00:00:00 2001
From: Nikita Malyavin <nikitamalyavin@gmail.com>
Date: Fri, 13 Feb 2026 15:42:18 +0100
Subject: [PATCH 5/6] Fix versioning.foreign crash

The problem is row_update_vers_insert invoked before the cascade update.
Cascade update relies on pre-defined node->pcur, and an insert can
invalidate the cursor, if b-tree node split happens.

One possible solution is to move the versioned insert after cascade
update.

This patch goes the described way, but also moves versioned insert to
the sql layer.

We have to re-set row event bits in trg_event_map, because
node->is_delete is determined based on those values.

TODO is to fix versioning.foreign 'trx_id,unique' result mismatch.
---
 sql/sql_table.cc                      |  27 +++++-
 storage/innobase/handler/ha_innodb.cc |   9 +-
 storage/innobase/row/row0ins.cc       |   9 --
 storage/innobase/row/row0mysql.cc     | 131 +-------------------------
 4 files changed, 36 insertions(+), 140 deletions(-)

diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index ce608e361695b..9bdad048e3836 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -13938,6 +13938,14 @@ void update_virtual_fields_for_rows(TABLE *table)
 int sql_delete_row(TABLE *table)
 {
   THD *thd= table->in_use;
+  bool delete_history= thd->lex->vers_conditions.delete_history;
+  thd->lex->vers_conditions.delete_history = false;
+  SCOPE_EXIT([thd, delete_history]
+  {
+    thd->lex->vers_conditions.delete_history= delete_history;
+  });
+  table->pos_in_table_list->trg_event_map = trg2bit(TRG_EVENT_DELETE);
+
   int error= 0;
   bool trg_skip_row= false;
   // This ensures that triggers can correctly read virtual field values
@@ -13952,7 +13960,7 @@ int sql_delete_row(TABLE *table)
     return trg_skip_row ? HA_ERR_CASCADE_SQL : 0;
       
 
-  error= table->file->ha_delete_row(table->record[0]);
+  error= table->delete_row();
   if (error != 0) 
     return error;
 
@@ -13979,6 +13987,8 @@ int sql_update_row(TABLE *table)
   bool trg_skip_row= false;
   table->column_bitmaps_set(&table->s->all_set, &table->s->all_set);
 
+  table->pos_in_table_list->trg_event_map = trg2bit(TRG_EVENT_UPDATE);
+
   // This ensures that triggers can correctly read virtual field values
   update_virtual_fields_for_rows(table);
 
@@ -13994,9 +14004,23 @@ int sql_update_row(TABLE *table)
   }
 
   int error= table->file->ha_update_row(table->record[1], table->record[0]);
+
+  bool record_was_same= error == HA_ERR_RECORD_IS_THE_SAME;
+  if (record_was_same)
+    error= 0;
   if (error != 0)
     return error;
 
+  if (table->versioned(VERS_TIMESTAMP))
+  {
+    store_record(table, record[2]);
+    table->mark_columns_per_binlog_row_image();
+    error= vers_insert_history_row(table);
+    restore_record(table, record[2]);
+    if (error)
+      return error;
+  }
+
   if (table->triggers &&
       unlikely(table->triggers->process_triggers(thd, TRG_EVENT_UPDATE,
                                                  TRG_ACTION_AFTER, TRUE,
@@ -14005,4 +14029,3 @@ int sql_update_row(TABLE *table)
 
   return 0;
 }
-
diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index 3f49914f67b43..6d727616439c8 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -21540,7 +21540,7 @@ TABLE *find_sql_table_for_update_node(upd_node_t* node) {
 dberr_t 
 innodb_do_foreign_cascade(que_thr_t *thr, upd_node_t* node)
 {
-  bool is_delete= (node->is_delete == PLAIN_DELETE);
+  bool is_delete= node->is_delete;
 
   TABLE *maria_table= find_sql_table_for_update_node(node);
 
@@ -21597,6 +21597,11 @@ innodb_do_foreign_cascade(que_thr_t *thr, upd_node_t* node)
   if (handler->update_prebuilt_upd_buf())
     return DB_OUT_OF_MEMORY;
 
+  TABLE_LIST *tl = maria_table->pos_in_table_list;
+  uint8 old_trg_ops = tl->trg_event_map;
+  uint8 old_slave_fk_ops = tl->slave_fk_event_map;
+  tl->trg_event_map = tl->slave_fk_event_map = 0;
+
   auto *upd_node= prebuilt->upd_node;
   auto *upd_graph= prebuilt->upd_graph;
   prebuilt->upd_node= node;
@@ -21610,6 +21615,8 @@ innodb_do_foreign_cascade(que_thr_t *thr, upd_node_t* node)
                      : sql_update_row(maria_table);
   --thd->fk_cascade_depth;
 
+  tl->slave_fk_event_map = old_slave_fk_ops;
+  tl->trg_event_map = old_trg_ops;
   prebuilt->upd_node= upd_node;
   prebuilt->upd_graph= upd_graph;
   return convert_sql_error_to_dberr(maria_table->in_use, thr, err);
diff --git a/storage/innobase/row/row0ins.cc b/storage/innobase/row/row0ins.cc
index 03ab40b985474..da2fb53a55974 100644
--- a/storage/innobase/row/row0ins.cc
+++ b/storage/innobase/row/row0ins.cc
@@ -1316,15 +1316,6 @@ row_ins_foreign_check_on_constraint(
 		}
 	}
 
-	if (table->versioned() && cascade->is_delete != PLAIN_DELETE
-	    && cascade->update->affects_versioned()) {
-		ut_ad(!cascade->historical_heap);
-		cascade->historical_heap = mem_heap_create(srv_page_size);
-		cascade->historical_row = row_build(
-			ROW_COPY_DATA, clust_index, clust_rec, NULL, table,
-			NULL, NULL, NULL, cascade->historical_heap);
-	}
-
 	/* Store pcur position and initialize or store the cascade node
 	pcur stored position */
 
diff --git a/storage/innobase/row/row0mysql.cc b/storage/innobase/row/row0mysql.cc
index 7bb3c9eadcabf..55063180aeeab 100644
--- a/storage/innobase/row/row0mysql.cc
+++ b/storage/innobase/row/row0mysql.cc
@@ -1815,124 +1815,6 @@ row_unlock_for_mysql(
 @param	buf	Buffer to hold start time data */
 void thd_get_query_start_data(THD *thd, char *buf);
 
-/** Insert history row when evaluating foreign key referential action.
-
-1. Create new dtuple_t 'row' from node->historical_row;
-2. Update its row_end to current timestamp;
-3. Insert it to a table;
-4. Update table statistics.
-
-This is used in UPDATE CASCADE/SET NULL of a system versioned referenced table.
-
-node->historical_row: dtuple_t containing pointers of row changed by referential
-action.
-
-@param[in]	thr	current query thread
-@param[in]	node	a node which just updated a row in a foreign table
-@return DB_SUCCESS or some error */
-static dberr_t row_update_vers_insert(que_thr_t* thr, upd_node_t* node)
-{
-	trx_t* trx = thr_get_trx(thr);
-	dfield_t* row_end;
-	char row_end_data[8];
-	dict_table_t* table = node->table;
-	const unsigned zip_size = table->space->zip_size();
-	ut_ad(table->versioned());
-
-	dtuple_t*       row;
-	const ulint     n_cols        = dict_table_get_n_cols(table);
-	const ulint     n_v_cols      = dict_table_get_n_v_cols(table);
-
-	ut_ad(n_cols == dtuple_get_n_fields(node->historical_row));
-	ut_ad(n_v_cols == dtuple_get_n_v_fields(node->historical_row));
-
-	row = dtuple_create_with_vcol(node->historical_heap, n_cols, n_v_cols);
-
-	dict_table_copy_types(row, table);
-
-	ins_node_t* insert_node =
-		ins_node_create(INS_DIRECT, table, node->historical_heap);
-
-	if (!insert_node) {
-		trx->error_state = DB_OUT_OF_MEMORY;
-		goto exit;
-	}
-
-	insert_node->common.parent = thr;
-	ins_node_set_new_row(insert_node, row);
-
-	ut_ad(n_cols > DATA_N_SYS_COLS);
-	// Exclude DB_ROW_ID, DB_TRX_ID, DB_ROLL_PTR
-	for (ulint i = 0; i < n_cols - DATA_N_SYS_COLS; i++) {
-		dfield_t *src= dtuple_get_nth_field(node->historical_row, i);
-		dfield_t *dst= dtuple_get_nth_field(row, i);
-		dfield_copy(dst, src);
-		if (dfield_is_ext(src)) {
-			byte *field_data
-				= static_cast<byte*>(dfield_get_data(src));
-			ulint ext_len;
-			ulint field_len = dfield_get_len(src);
-
-			ut_a(field_len >= BTR_EXTERN_FIELD_REF_SIZE);
-
-			ut_a(memcmp(field_data + field_len
-				     - BTR_EXTERN_FIELD_REF_SIZE,
-				     field_ref_zero,
-				     BTR_EXTERN_FIELD_REF_SIZE));
-
-			byte *data = btr_copy_externally_stored_field(
-				&ext_len, field_data, zip_size, field_len,
-				node->historical_heap);
-			dfield_set_data(dst, data, ext_len);
-		}
-	}
-
-	for (ulint i = 0; i < n_v_cols; i++) {
-		dfield_t *dst= dtuple_get_nth_v_field(row, i);
-		dfield_t *src= dtuple_get_nth_v_field(node->historical_row, i);
-		dfield_copy(dst, src);
-	}
-
-	node->historical_row = NULL;
-
-	row_end = dtuple_get_nth_field(row, table->vers_end);
-	if (dict_table_get_nth_col(table, table->vers_end)->vers_native()) {
-		mach_write_to_8(row_end_data, trx->id);
-		dfield_set_data(row_end, row_end_data, 8);
-	} else {
-		thd_get_query_start_data(trx->mysql_thd, row_end_data);
-		dfield_set_data(row_end, row_end_data, 7);
-	}
-
-	for (;;) {
-		thr->run_node = insert_node;
-		thr->prev_node = insert_node;
-
-		row_ins_step(thr);
-
-		switch (trx->error_state) {
-		case DB_LOCK_WAIT:
-			if (lock_wait(thr) == DB_SUCCESS) {
-				continue;
-			}
-
-			/* fall through */
-		default:
-			/* Other errors are handled for the parent node. */
-			goto exit;
-
-		case DB_SUCCESS:
-			dict_stats_update_if_needed(table, *trx);
-			goto exit;
-		}
-	}
-exit:
-	que_graph_free_recursive(insert_node);
-	mem_heap_free(node->historical_heap);
-	node->historical_heap = NULL;
-	return trx->error_state;
-}
-
 /**********************************************************************//**
 Does a cascaded delete or set null in a foreign key operation.
 @return error code or DB_SUCCESS */
@@ -1946,16 +1828,9 @@ row_update_cascade_for_mysql(
 {
 	trx_t* trx = thr_get_trx(thr);
 
-	if (table->versioned()) {
-		if (node->is_delete == PLAIN_DELETE) {
-                  node->vers_make_delete(trx);
-                } else if (node->update->affects_versioned()) {
-			dberr_t err = row_update_vers_insert(thr, node);
-			if (err != DB_SUCCESS) {
-				return err;
-			}
-                        node->vers_make_update(trx);
-                }
+	if (table->versioned() && node->is_delete != PLAIN_DELETE &&
+	  node->update->affects_versioned()) {
+		node->vers_make_update(trx);
 	}
 
 	for (;;) {

From 4d122cd0f3d2c85923dbd30152ab00f22ac5e978 Mon Sep 17 00:00:00 2001
From: Nikita Malyavin <nikitamalyavin@gmail.com>
Date: Fri, 13 Feb 2026 17:15:18 +0100
Subject: [PATCH 6/6] MDEV-31942 Online alter: support cascade foreign keys

All the technical provisioning was done yet by
MDEV-12302 Execute triggers for foreign key updates/deletes

As it executes ha_update_row and ha_delete_row directly.

All that is left is remove the restriction and add the tests.
---
 mysql-test/main/alter_table_online.result     |  9 +-
 mysql-test/main/alter_table_online.test       | 12 +--
 .../main/alter_table_online_debug.result      | 89 +++++++++++++++++-
 mysql-test/main/alter_table_online_debug.test | 91 ++++++++++++++++++-
 sql/sql_table.cc                              | 21 -----
 5 files changed, 185 insertions(+), 37 deletions(-)

diff --git a/mysql-test/main/alter_table_online.result b/mysql-test/main/alter_table_online.result
index 45351daea0fea..c7b1df0ed23cb 100644
--- a/mysql-test/main/alter_table_online.result
+++ b/mysql-test/main/alter_table_online.result
@@ -91,14 +91,12 @@ references t1 (a)
 on update cascade) engine=InnoDB;
 insert into t2 values (1),(2),(3);
 alter table t2 add c int, algorithm=copy, lock=none;
-ERROR 0A000: LOCK=NONE is not supported. Reason: ON UPDATE CASCADE. Try LOCK=SHARED
-alter table t2 add c int, algorithm=inplace, lock=none;
+alter table t2 add d int, algorithm=inplace, lock=none;
 create or replace table t2 (b int, foreign key (b)
 references t1 (a)
 on delete set null) engine=InnoDB;
 alter table t2 add c int, algorithm=copy, lock=none;
-ERROR 0A000: LOCK=NONE is not supported. Reason: ON DELETE SET NULL. Try LOCK=SHARED
-alter table t2 add c int, algorithm=inplace, lock=none;
+alter table t2 add d int, algorithm=inplace, lock=none;
 create or replace table t2 (b int, foreign key (b)
 references t1 (a)
 on delete no action) engine=InnoDB;
@@ -116,8 +114,7 @@ create table t2 (a int references t1 (a),
 b int references t1 (b) on update cascade) engine=InnoDB;
 insert into t2 values (1, 1),(2, 2);
 alter table t2 add c int, algorithm=copy, lock=none;
-ERROR 0A000: LOCK=NONE is not supported. Reason: ON UPDATE CASCADE. Try LOCK=SHARED
-alter table t2 add c int, algorithm=copy;
+alter table t2 add e int, algorithm=copy;
 alter table t2 add d int, algorithm=inplace;
 drop table t2, t1;
 #
diff --git a/mysql-test/main/alter_table_online.test b/mysql-test/main/alter_table_online.test
index 6416a3e79d1ce..7d5f89bccb914 100644
--- a/mysql-test/main/alter_table_online.test
+++ b/mysql-test/main/alter_table_online.test
@@ -70,6 +70,8 @@ DROP TABLE t;
 
 --echo #
 --echo # MDEV-29068 Cascade foreign key updates do not apply in online alter
+--echo # per MDEV-31942 Online alter: support cascade foreign keys
+--echo # The limitation is lifted
 --echo #
 create table t1 (a int primary key) engine=InnoDB;
 insert into t1 values (1),(2),(3);
@@ -78,17 +80,16 @@ create table t2 (b int, foreign key (b)
                         on update cascade) engine=InnoDB;
 insert into t2 values (1),(2),(3);
 
---error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
+
 alter table t2 add c int, algorithm=copy, lock=none;
-alter table t2 add c int, algorithm=inplace, lock=none;
+alter table t2 add d int, algorithm=inplace, lock=none;
 
 create or replace table t2 (b int, foreign key (b)
                             references t1 (a)
                             on delete set null) engine=InnoDB;
 
---error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
 alter table t2 add c int, algorithm=copy, lock=none;
-alter table t2 add c int, algorithm=inplace, lock=none;
+alter table t2 add d int, algorithm=inplace, lock=none;
 
 create or replace table t2 (b int, foreign key (b)
                             references t1 (a)
@@ -111,9 +112,8 @@ create table t2 (a int references t1 (a),
                  b int references t1 (b) on update cascade) engine=InnoDB;
 insert into t2 values (1, 1),(2, 2);
 
---error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
 alter table t2 add c int, algorithm=copy, lock=none;
-alter table t2 add c int, algorithm=copy;
+alter table t2 add e int, algorithm=copy;
 alter table t2 add d int, algorithm=inplace;
 # Cleanup
 drop table t2, t1;
diff --git a/mysql-test/main/alter_table_online_debug.result b/mysql-test/main/alter_table_online_debug.result
index 537556e2e2db9..c4ecb85815ce7 100644
--- a/mysql-test/main/alter_table_online_debug.result
+++ b/mysql-test/main/alter_table_online_debug.result
@@ -1830,8 +1830,93 @@ alter table t add index (a), algorithm=copy, lock=none;
 connection default;
 drop table t;
 set global default_storage_engine= MyISAM;
-disconnect con1;
-disconnect con2;
 #
 # End of 11.2 tests
 #
+# MDEV-12302: Execute triggers for foreign key updates/deletes
+# This unblocks online alter table for cascade FK
+create table t1 (a int primary key) engine=InnoDB;
+insert into t1 values (1),(2),(3);
+create table t2 (b int unique references t1 (a) on delete cascade) engine=InnoDB;
+insert into t2 values (1),(2),(3);
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+alter table t2 add c int default (b+1), algorithm=copy, lock=none;
+connection con1;
+set debug_sync='now WAIT_FOR copy_end';
+delete from t1 where a = 1;
+set debug_sync='now SIGNAL proceed';
+connection default;
+select * from t2;
+b	c
+2	3
+3	4
+create or replace table t2 (b int, foreign key (b)
+references t1 (a)
+on delete set null) engine=InnoDB;
+insert into t2 values (2),(3);
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+alter table t2 add c int default (b+1), algorithm=copy, lock=none;
+connection con1;
+set debug_sync='now WAIT_FOR copy_end';
+delete from t1 where a = 2;
+set debug_sync='now SIGNAL proceed';
+connection default;
+select * from t2;
+b	c
+NULL	NULL
+3	4
+select * from t1;
+a
+3
+drop table t2, t1;
+create table t1 (a int primary key, b int unique) engine=InnoDB;
+insert into t1 values (1, 1),(2, 2),(3, 3);
+create table t2 (a int references t1 (a) on update cascade,
+b int references t1 (b) on update cascade) engine=InnoDB;
+insert into t2 values (1, 1),(2, 2),(3, 3);
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+alter table t2 add c int default (b+1), algorithm=copy, lock=none;
+connection con1;
+set debug_sync='now WAIT_FOR copy_end';
+update t1 set a = 5, b = 6 where a = 2;
+set debug_sync='now SIGNAL proceed';
+connection default;
+select * from t2;
+a	b	c
+1	1	2
+5	6	7
+3	3	4
+select * from t1;
+a	b
+1	1
+3	3
+5	6
+drop table t2, t1;
+create table t1 (a int primary key, b int unique) engine=InnoDB;
+insert into t1 values (1, 1),(2, 2),(3, 3);
+create table t2 (a int references t1 (a) on update cascade,
+b int references t1 (b) on update set null) engine=InnoDB;
+insert into t2 values (1, 1),(2, 2),(3, 3);
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+alter table t2 add c int default (b+1), algorithm=copy, lock=none;
+connection con1;
+set debug_sync='now WAIT_FOR copy_end';
+update t1 set a=5, b = 6 where a = 2;
+set debug_sync='now SIGNAL proceed';
+connection default;
+select * from t2;
+a	b	c
+1	1	2
+5	NULL	NULL
+3	3	4
+select * from t1;
+a	b
+1	1
+3	3
+5	6
+drop table t2, t1;
+#
+# End of 11.3 tests
+#
+disconnect con1;
+disconnect con2;
diff --git a/mysql-test/main/alter_table_online_debug.test b/mysql-test/main/alter_table_online_debug.test
index 1271e0f13e35f..6b0a6ac24d955 100644
--- a/mysql-test/main/alter_table_online_debug.test
+++ b/mysql-test/main/alter_table_online_debug.test
@@ -2103,8 +2103,95 @@ drop table t;
 
 eval set global default_storage_engine= $default_storage_engine;
 
---disconnect con1
---disconnect con2
+
 --echo #
 --echo # End of 11.2 tests
 --echo #
+
+
+--echo # MDEV-31942 Online alter: support cascade foreign keys
+create table t1 (a int primary key) engine=InnoDB;
+insert into t1 values (1),(2),(3);
+
+create table t2 (b int unique references t1 (a) on delete cascade) engine=InnoDB;
+insert into t2 values (1),(2),(3);
+
+
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+send alter table t2 add c int default (b+1), algorithm=copy, lock=none;
+connection con1;
+
+set debug_sync='now WAIT_FOR copy_end';
+delete from t1 where a = 1;
+set debug_sync='now SIGNAL proceed';
+connection default;
+reap;
+select * from t2;
+
+create or replace table t2 (b int, foreign key (b)
+  references t1 (a)
+  on delete set null) engine=InnoDB;
+insert into t2 values (2),(3);
+
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+send alter table t2 add c int default (b+1), algorithm=copy, lock=none;
+
+connection con1;
+set debug_sync='now WAIT_FOR copy_end';
+delete from t1 where a = 2;
+set debug_sync='now SIGNAL proceed';
+connection default;
+reap;
+select * from t2;
+select * from t1;
+
+drop table t2, t1;
+
+create table t1 (a int primary key, b int unique) engine=InnoDB;
+insert into t1 values (1, 1),(2, 2),(3, 3);
+create table t2 (a int references t1 (a) on update cascade,
+                 b int references t1 (b) on update cascade) engine=InnoDB;
+insert into t2 values (1, 1),(2, 2),(3, 3);
+
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+send alter table t2 add c int default (b+1), algorithm=copy, lock=none;
+
+connection con1;
+set debug_sync='now WAIT_FOR copy_end';
+update t1 set a = 5, b = 6 where a = 2;
+set debug_sync='now SIGNAL proceed';
+connection default;
+reap;
+select * from t2;
+select * from t1;
+
+drop table t2, t1;
+
+create table t1 (a int primary key, b int unique) engine=InnoDB;
+insert into t1 values (1, 1),(2, 2),(3, 3);
+create table t2 (a int references t1 (a) on update cascade,
+                 b int references t1 (b) on update set null) engine=InnoDB;
+insert into t2 values (1, 1),(2, 2),(3, 3);
+
+set debug_sync= 'alter_table_copy_end SIGNAL copy_end WAIT_FOR proceed';
+send alter table t2 add c int default (b+1), algorithm=copy, lock=none;
+
+connection con1;
+set debug_sync='now WAIT_FOR copy_end';
+update t1 set a=5, b = 6 where a = 2;
+set debug_sync='now SIGNAL proceed';
+connection default;
+reap;
+select * from t2;
+select * from t1;
+
+# Cleanup
+drop table t2, t1;
+
+--echo #
+--echo # End of 11.3 tests
+--echo #
+
+
+--disconnect con1
+--disconnect con2
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 9bdad048e3836..aaf46c331c7d5 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -10626,27 +10626,6 @@ const char *online_alter_check_supported(THD *thd,
   if (!*online)
     return "BIGINT GENERATED ALWAYS AS ROW_START";
 
-  List<FOREIGN_KEY_INFO> fk_list;
-  table->file->get_foreign_key_list(thd, &fk_list);
-  for (auto &fk: fk_list)
-  {
-    if (fk_modifies_child(fk.delete_method) ||
-        fk_modifies_child(fk.update_method))
-    {
-      *online= false;
-      // Don't fall to a common unsupported case to avoid heavy string ops.
-      if (alter_info->requested_lock == Alter_info::ALTER_TABLE_LOCK_NONE)
-      {
-        return fk_modifies_child(fk.delete_method)
-               ? thd->strcat({STRING_WITH_LEN("ON DELETE ")},
-                             *fk_option_name(fk.delete_method)).str
-               : thd->strcat({STRING_WITH_LEN("ON UPDATE ")},
-                             *fk_option_name(fk.update_method)).str;
-      }
-      return NULL;
-    }
-  }
-
   for (auto &c: alter_info->create_list)
   {
     *online= c.field || !(c.flags & AUTO_INCREMENT_FLAG);