PostgreSQL two different ways to generate a UUID: gen_random_uuid vs uuid_generate_v4?

Question

What is the difference between the following two functions

• gen_random_uuid() provided by pgcrypto extension
• uuid_generate_v4() provided by uuid-ossp extension

Are they both the same behind the scenes? Any performance impacts on using one?

Answer 1

Are they the same?

No.

The Postgres documetation for uuid-ossp suggests using gen_random_uuid() If you only need randomly-generated (version 4) UUIDs,

The uuid-ossp extension also provides other types of UUID (such as mac-addresses based)

The difference?

I looked at the source and discovered that

• uuid_generate_v4() uses arc4random to determine the random part.

• gen_random_uuid() uses fortuna instead.

Other than that they do the same job.

Notes:

• gen_random_uuid() from the pgcrypto module is now deprecated, because it is natively part of PostgreSQL (since PostgreSQL version 13).
• uuid_generate_v4() still requires the uuid-ossp module.