Changing a string column of ORC table to boolean sets values to be 'NULL'

0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> set hive.metastore.disallow.incompatible.col.type.changes=false;
No rows affected (0.015 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> set hive.exec.dynamic.partition.mode=nonstrict;
No rows affected (0.003 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> drop table test;
No rows affected (0.224 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> create table test (s string) stored as orc;
No rows affected (0.098 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> insert into table test values ('true');
No rows affected (1.091 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> select * from test;
+---------+--+
| test.s  |
+---------+--+
| true    |
+---------+--+
1 row selected (0.114 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> alter table test change column s s boolean;
No rows affected (0.167 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> select * from test;
+---------+--+
| test.s  |
+---------+--+
| NULL    |
+---------+--+
1 row selected (0.098 seconds)

0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> set hive.metastore.disallow.incompatible.col.type.changes=false;
No rows affected (0.013 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> set hive.exec.dynamic.partition.mode=nonstrict;
No rows affected (0.006 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> drop table test;
No rows affected (0.224 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> create table test (s string) stored as textfile;
No rows affected (0.116 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> insert into table test values ('true');
No rows affected (1.799 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> select * from test;
+---------+--+
| test.s  |
+---------+--+
| true    |
+---------+--+
1 row selected (0.085 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> alter table test change column s s boolean;
No rows affected (0.141 seconds)
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2>
0: jdbc:hive2://os-r7-rcmpc-nat-u-hiveserver2> select * from test;
+---------+--+
| test.s  |
+---------+--+
| true    |
+---------+--+
1 row selected (0.093 seconds)