MDEV-33942 View cuts off the end of string with the utf8 character set in INSERT function

Item_func_insert::fix_length_and_dec() incorrectly calculated max_length
when its collation.collation evaluated to my_charset_bin.

Fixing the code to calculate max_length in terms of octets rather
than in terms of characters when collation.collation is my_charset_bin.

Author: abarkov

mysql-test/main/func_str.result

@@ -5344,5 +5344,16 @@ left('hello', 4294967295)
 hello
 drop view v1;
 #
+# MDEV-33942 View cuts off the end of string with the utf8 character set in INSERT function
+#
+SELECT HEX(INSERT(_utf8 0xD18FD18E, 2, 1, 0x20));
+HEX(INSERT(_utf8 0xD18FD18E, 2, 1, 0x20))
+D120D18E
+CREATE VIEW v1 AS SELECT HEX(INSERT(_utf8 0xD18FD18E, 2, 1, 0x20));
+SELECT * FROM v1;
+HEX(INSERT(_utf8 0xD18FD18E, 2, 1, 0x20))
+D120D18E
+DROP VIEW v1;
+#
 # End of 10.6 tests
 #

mysql-test/main/func_str.test

@@ -2393,6 +2393,16 @@ create view v1 as select left('hello', 4294967295);
 select * from v1;
 drop view v1;
 
+--echo #
+--echo # MDEV-33942 View cuts off the end of string with the utf8 character set in INSERT function
+--echo #
+
+SELECT HEX(INSERT(_utf8 0xD18FD18E, 2, 1, 0x20));
+CREATE VIEW v1 AS SELECT HEX(INSERT(_utf8 0xD18FD18E, 2, 1, 0x20));
+SELECT * FROM v1;
+DROP VIEW v1;
+
+
 --echo #
 --echo # End of 10.6 tests
 --echo #

sql/item_strfunc.cc

@@ -1562,8 +1562,12 @@ bool Item_func_insert::fix_length_and_dec()
   // Handle character set for args[0] and args[3].
   if (agg_arg_charsets_for_string_result(collation, args, 2, 3))
     return TRUE;
-  char_length= ((ulonglong) args[0]->max_char_length() +
-                (ulonglong) args[3]->max_char_length());
+  if (collation.collation == &my_charset_bin)
+    char_length= (ulonglong) args[0]->max_length +
+                 (ulonglong) args[3]->max_length;
+  else
+    char_length= ((ulonglong) args[0]->max_char_length() +
+                  (ulonglong) args[3]->max_char_length());
   fix_char_length_ulonglong(char_length);
   return FALSE;
 }