space character in field is ignored

```
in:
...
type: mysql
query: |-
SELECT metaID, metaName, metaDesc, createDate FROM A

out:
...
type: mysql
create_table_constraint: primary key (metaID), UNIQUE KEY `unique_index` (`metaName`)
mode: merge
options: {useUnicode: true, characterEncoding: UTF-8}
column_options:
...
```

*metaName* column is already unique key in source db.
but error is caused by unique key
error message is
```
Duplicate entry 'somevalue?' for key 'unique_index'
```

i think the reason is...

| metaName |
|--------------|
| 'somevalue' |
| 'somevalue ' |

(with space at the end)

i think embulk input plugin ignore a space.
is there any solution?