Updating unindexed values with postgresql question
PostgreSQL doesn't table-lock on update, it row-locks.


  You need to update this table so all occurrences of a particular string in the “type” column are replaced with another string. 


That's simple,

UPDATE apps
SET type = regexp_replace(type, 'SearchRegex', 'Replacement', 'g')  
WHERE type ~ 'SearchRegex';