From 62287320d43fffda20f11d8672ef35fc5d9f6d82 Mon Sep 17 00:00:00 2001
From: Oleksandr Byelkin <sanja@mariadb.com>
Date: Tue, 23 Apr 2024 11:37:11 +0200
Subject: [PATCH] MDEV-33790 Incorrect DEFAULT expression evaluated in UPDATE

The problem was that Item_default_value::associate_with_target_field
assigned passed as argument field as an argument which changed argument
in case of default() call with certain field (i.e. deault(field)).

There is no way to get wrong field in constructor so we will not reassign
parameter.
---
 mysql-test/main/function_defaults.result | 25 ++++++++++++++++++++++++
 mysql-test/main/function_defaults.test   | 23 ++++++++++++++++++++++
 sql/item.cc                              | 10 +++++++---
 3 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/mysql-test/main/function_defaults.result b/mysql-test/main/function_defaults.result
index 697e2e0d063..41bd0140a23 100644
--- a/mysql-test/main/function_defaults.result
+++ b/mysql-test/main/function_defaults.result
@@ -3145,3 +3145,28 @@ a	b	c
 2	2010-10-10 10:10:10	x
 drop table t1;
 set timestamp=default;
+#
+# MDEV-33790: Incorrect DEFAULT expression evaluated in UPDATE
+#
+create table t1 (
+a int,
+b timestamp default '2010-10-10 10:10:10' on update now(),
+c varchar(100) default 'x');
+create table t2 (a int primary key);
+insert t1 (a) values (1),(2);
+insert t2 (a) values (1),(2);
+select * from t1;
+a	b	c
+1	2010-10-10 10:10:10	x
+2	2010-10-10 10:10:10	x
+set timestamp=unix_timestamp('2011-11-11 11-11-11');
+update t1,t2 set b=default, c=default(b) where t1.a=1 and t1.a= t2.a;
+select * from t1;
+a	b	c
+1	2010-10-10 10:10:10	2010-10-10 10:10:10
+2	2010-10-10 10:10:10	x
+drop table t1, t2;
+set timestamp=default;
+#
+# End of 10.4 tests
+#
diff --git a/mysql-test/main/function_defaults.test b/mysql-test/main/function_defaults.test
index dd3ba109b2a..59776118e56 100644
--- a/mysql-test/main/function_defaults.test
+++ b/mysql-test/main/function_defaults.test
@@ -67,3 +67,26 @@ update t1 set b=default, c=default(b) where a=1;
 select * from t1;
 drop table t1;
 set timestamp=default;
+
+--echo #
+--echo # MDEV-33790: Incorrect DEFAULT expression evaluated in UPDATE
+--echo #
+
+create table t1 (
+  a int,
+  b timestamp default '2010-10-10 10:10:10' on update now(),
+  c varchar(100) default 'x');
+create table t2 (a int primary key);
+insert t1 (a) values (1),(2);
+insert t2 (a) values (1),(2);
+
+select * from t1;
+set timestamp=unix_timestamp('2011-11-11 11-11-11');
+update t1,t2 set b=default, c=default(b) where t1.a=1 and t1.a= t2.a;
+select * from t1;
+drop table t1, t2;
+set timestamp=default;
+
+--echo #
+--echo # End of 10.4 tests
+--echo #
diff --git a/sql/item.cc b/sql/item.cc
index f70775b86e8..c951a94b226 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -9748,11 +9748,15 @@ Item *Item_default_value::transform(THD *thd, Item_transformer transformer,
 }
 
 
-bool Item_default_value::associate_with_target_field(THD *thd,
-                                                     Item_field *field)
+bool Item_default_value::
+  associate_with_target_field(THD *thd,
+                              Item_field *field __attribute__((unused)))
 {
   m_associated= true;
-  arg= field;
+  /*
+    arg set correctly in constructor (can also differ from field if
+    it is function with an argument)
+  */
   return tie_field(thd);
 }