Bug #15439: UDF name case handling forces DELETE FROM mysql.func to remove

            the UDF
When deleting a user defined function MySQL must remove it from both the
in-memory hash table and the mysql.proc system table.
Finding (and removal therefore) from the internal hash table is case 
insensitive (or whatever the default charset is), whereas finding and 
removal from the system table is case sensitive.
As a result if you supply a function name that is not in the same character
case to DROP FUNCTION the server will remove the function only from the
in-memory hash table and will keep the row in mysql.proc system table.
This will cause inconsistency between the two structures (that is fixed
only by restarting the server).
Fixed by using the name in the precise case (from the in-memory hash table)
to delete the row in the mysql.proc system table. 

mysql-test/r/udf.result

@@ -194,6 +194,17 @@ DROP FUNCTION sequence;
 DROP FUNCTION lookup;
 DROP FUNCTION reverse_lookup;
 DROP FUNCTION avgcost;
+select * from mysql.func;
+name	ret	dl	type
+CREATE FUNCTION is_const RETURNS STRING SONAME "UDF_EXAMPLE_LIB";
+select IS_const(3);
+IS_const(3)
+const
+drop function IS_const;
+select * from mysql.func;
+name	ret	dl	type
+select is_const(3);
+ERROR 42000: FUNCTION test.is_const does not exist
 CREATE FUNCTION is_const RETURNS STRING SONAME "UDF_EXAMPLE_LIB";
 select
 is_const(3) as const,

mysql-test/t/udf.test

@@ -187,6 +187,23 @@ DROP FUNCTION lookup;
 DROP FUNCTION reverse_lookup;
 DROP FUNCTION avgcost;
 
+#
+# Bug #15439: UDF name case handling forces DELETE FROM mysql.func to remove 
+#             the UDF
+# 
+select * from mysql.func;
+--replace_result $UDF_EXAMPLE_LIB UDF_EXAMPLE_LIB
+eval CREATE FUNCTION is_const RETURNS STRING SONAME "$UDF_EXAMPLE_LIB";
+
+select IS_const(3);
+
+drop function IS_const;
+
+select * from mysql.func;
+
+--error 1305
+select is_const(3);
+
 #
 # Bug#18761: constant expression as UDF parameters not passed in as constant
 #

sql/sql_udf.cc

@@ -536,7 +536,7 @@ int mysql_drop_function(THD *thd,const LEX_STRING *udf_name)
   tables.table_name= tables.alias= (char*) "func";
   if (!(table = open_ltable(thd,&tables,TL_WRITE)))
     goto err;
-  table->field[0]->store(udf_name->str, udf_name->length, system_charset_info);
+  table->field[0]->store(udf->name.str, udf->name.length, &my_charset_bin);
   table->file->extra(HA_EXTRA_RETRIEVE_ALL_COLS);
   if (!table->file->index_read_idx(table->record[0], 0,
 				   (byte*) table->field[0]->ptr,