From a773916238d9bece75458b9548e08fac303cdc8a Mon Sep 17 00:00:00 2001
From: "ramil@mysql.com" <>
Date: Thu, 17 Mar 2005 10:24:50 +0400
Subject: [PATCH] A fix (bug #8942: SUBSTRING_INDEX in UPDATE causes internal
 loop).

---
 mysql-test/r/update.result |  7 +++++++
 mysql-test/t/update.test   | 10 ++++++++++
 sql/key.cc                 |  2 +-
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/mysql-test/r/update.result b/mysql-test/r/update.result
index 7810d52d156..9ca92fe75df 100644
--- a/mysql-test/r/update.result
+++ b/mysql-test/r/update.result
@@ -209,3 +209,10 @@ insert into t1 values (1, "t1c2-1", 10), (2, "t1c2-2", 20);
 update t1 left join t2 on t1.c1 = t2.c1 set t2.c2 = "t2c2-1";
 update t1 left join t2 on t1.c1 = t2.c1 set t2.c2 = "t2c2-1" where t1.c3 = 10;
 drop table t1, t2;
+create table t1 (a int, b char(255), key(a, b(20)));
+insert into t1 values (0, '1');
+update t1 set b = b + 1 where a = 0;
+select * from t1;
+a	b
+0	2
+drop table t1;
diff --git a/mysql-test/t/update.test b/mysql-test/t/update.test
index 62439dcc51b..6c7b450f763 100644
--- a/mysql-test/t/update.test
+++ b/mysql-test/t/update.test
@@ -164,3 +164,13 @@ insert into t1 values (1, "t1c2-1", 10), (2, "t1c2-2", 20);
 update t1 left join t2 on t1.c1 = t2.c1 set t2.c2 = "t2c2-1";
 update t1 left join t2 on t1.c1 = t2.c1 set t2.c2 = "t2c2-1" where t1.c3 = 10;
 drop table t1, t2;
+
+#
+# Bug #8942: a problem with update and partial key part
+#
+
+create table t1 (a int, b char(255), key(a, b(20)));
+insert into t1 values (0, '1');
+update t1 set b = b + 1 where a = 0;
+select * from t1;
+drop table t1;
diff --git a/sql/key.cc b/sql/key.cc
index 0a5937fc881..52eb108a5df 100644
--- a/sql/key.cc
+++ b/sql/key.cc
@@ -265,7 +265,7 @@ bool check_if_key_used(TABLE *table, uint idx, List<Item> &fields)
     f.rewind();
     while ((field=(Item_field*) f++))
     {
-      if (key_part->field == field->field)
+      if (key_part->field->eq(field->field))
 	return 1;
     }
   }