Missing quote in db_add_column $attributes default parameter

As per documentation, the 'default' value in $attributes array supposed to be "''":-

db_add_column($ret = array(), 'files', 'origname', 'varchar(255)', array('not null' => TRUE, 'default' => ''));

db_add_column($ret = array(), 'files', 'origname', 'varchar(255)', array('not null' => TRUE, 'default' => "''"));

Otherwise you would get an error when running update.php:-

warning: pg_query() [function.pg-query]: Query failed: ERROR: syntax error at end of input LINE 1: ALTER TABLE files ALTER origname SET default ^ ....