How large can an id get in postgresql

Question

I am using postgresql, and was wondering how large

id INTEGER PRIMARY KEY

can get compared to

id SERIAL PRIMARY KEY
         


        

Answer 1

The data types smallserial, serial and bigserial are not true types, but merely a notational convenience for creating unique identifier columns (similar to the AUTO_INCREMENT property supported by some other databases)

A bigserial is 8 bytes long. If that is not enough it is possible to use the 128 bits uuid:

create table t (
    id uuid primary key
);
insert into t (id)
select uuid_generate_v1mc();
select * from t;
                  id                  
--------------------------------------
 916bf7e6-f0c2-11e2-8d14-d372d5ab075f

The uuid_generate_v1mc function is provided by the uuid-ossp module

The main advantage of the uuid functions is that they generate an id that is very likely to be unique among different systems. A serial will have collisions between those systems.