PostgreSQL:

ALTER DATABASE

ALTER DATABASE name [ [ WITH ] option [ ... ] ]

where option can be:

CONNECTION LIMIT connlimit

ALTER DATABASE name RENAME TO new_name

ALTER DATABASE name OWNER TO new_owner

ALTER DATABASE name SET TABLESPACE new_tablespace

ALTER DATABASE name SET configuration_parameter { TO | = } { value | DEFAULT }
ALTER DATABASE name SET configuration_parameter FROM CURRENT
ALTER DATABASE name RESET configuration_parameter
ALTER DATABASE name RESET ALL

Example

ALTER DATABASE test SET enable_indexscan TO off;