diff --git a/mysql-test/t/func_group.test b/mysql-test/t/func_group.test
index 1bf924100a9..fed19cbe07c 100644
--- a/mysql-test/t/func_group.test
+++ b/mysql-test/t/func_group.test
@@ -348,7 +348,9 @@ insert into t1 values (3,1);
 select a,count(b), sum(b), avg(b), std(b), min(b), max(b), bit_and(b), bit_or(b) from t1 group by a;
 select SQL_BIG_RESULT a,count(b), sum(b), avg(b), std(b), min(b), max(b), bit_and(b), bit_or(b) from t1 group by a;
 drop table t1;
+--disable_warnings
 create table t1 (USR_ID integer not null, MAX_REQ integer not null, constraint PK_SEA_USER primary key (USR_ID)) type=InnoDB;
+--enable_warnings
 insert into t1 values (1, 3);
 select count(*) + MAX_REQ - MAX_REQ + MAX_REQ - MAX_REQ + MAX_REQ - MAX_REQ + MAX_REQ - MAX_REQ + MAX_REQ - MAX_REQ from t1 group by MAX_REQ;
 select Case When Count(*) < MAX_REQ Then 1 Else 0 End from t1 where t1.USR_ID = 1 group by MAX_REQ;
diff --git a/mysql-test/t/preload.test b/mysql-test/t/preload.test
old mode 100755
new mode 100644
diff --git a/mysys/tree.c b/mysys/tree.c
index a3b69ebff5e..91d2f9771b5 100644
--- a/mysys/tree.c
+++ b/mysys/tree.c
@@ -46,6 +46,16 @@
   Implemented by monty.
 */
 
+/*
+  NOTE:
+  tree->compare function should be ALWAYS called as
+    (*tree->compare)(custom_arg, ELEMENT_KEY(tree,element), key)
+  and not other way around, as
+    (*tree->compare)(custom_arg, key, ELEMENT_KEY(tree,element))
+
+  ft_boolean_search.c (at least) relies on that.
+*/
+
 #include "mysys_priv.h"
 #include <m_string.h>
 #include <my_tree.h>