What is uuid ossp in postgres

Question

I saw this in migration

enable_extension 'uuid-ossp'

As far as I know, uuid is a long unique string based on some RFCs and this allows db (in this case pg) to have a column type like uuid

my question is: why is this type of column needed, not just a row column? is it to replace a regular column with an integer id and instead indicate uuid as id?

Is there any advantage to using uuid since id instead of having a column of type string contains uuid?

Answer 1

, , uuid id , , .

:

• , /
• Postgres, .
• ( , )
• (, , users/1 (id), users/2, , - , ). , ,

:

• , id
• ( , , , , )
• ( UUID, id)

, :

• UUID ( ) ( , , )... UUID, : http://vimeo.com/61044807#t=15m04s
• Jeff Atwood ( StackOverflow) GUID: http://www.codinghorror.com/blog/2007/03/primary-keys-ids-versus-guids.html
• http://rny.io/rails/postgresql/2013/07/27/use-uuids-in-rails-4-with-postgresql.html
• http://blog.crowdint.com/2013/10/09/using-postgres-uuids-as-primary-keys-on-rails.html

Answer 2

uuid type. UUID - . -

select 'a'::uuid;
ERROR:  invalid input syntax for uuid: "a"

-, . UUID 16 , 33:

select
    pg_column_size('0123456789abcdef0123456789abcdef'),
    pg_column_size('0123456789abcdef0123456789abcdef'::uuid)
;
 pg_column_size | pg_column_size 
----------------+----------------
             33 |             16

uuid-ossp uuid.