ERROR: attribute number 6 exceeds number of columns 5

Run the attached script and you'll get: 

psql -f error.sql -d test 
psql:error.sql:37: ERROR: attribute number 6 exceeds number of columns 5

Splitting up the alter-table like this makes it work: 

alter table access
 add column start_timestamp timestamp not null DEFAULT CURRENT_TIMESTAMP,
 add column end_timestamp timestamp
 ;
 alter table access add column tsrange TSRANGE NOT NULL GENERATED ALWAYS AS 
(tsrange(start_timestamp, end_timestamp, '[)')) STORED
 ; 

-- 

Andreas Joseph Krogh