I am running a
REINDEX but it takes long time and still working. The application using the DB is not responding right now. Is there a safe way to stop it and do it another time?
PostgreSQL version is 8.4.
Yes, it's safe. Might take a while, though.
In future you might want to use "CREATE INDEX CONCURRENTLY", like dezso suggested, but first create new index, and then drop old one.