uuid1() is guaranteed to not produce any collisions (under the assumption you do not create too many of them at the same time). I wouldn’t use it if it’s important that there’s no connection between the uuid and the computer, as the mac address gets used to make it unique across computers. You can create … Read more
Advantages: Can generate them offline. Makes replication trivial (as opposed to int’s, which makes it REALLY hard) ORM’s usually like them Unique across applications. So We can use the PK’s from our CMS (guid) in our app (also guid) and know we are NEVER going to get a clash. Disadvantages: Larger space use, but space … Read more
Instead of breaking it down into individual fields, it’s easier to generate a random block of data and change the individual byte positions. You should also use a better random number generator than mt_rand(). According to RFC 4122 – Section 4.4, you need to change these fields: time_hi_and_version (bits 4-7 of 7th octet), clock_seq_hi_and_reserved (bit … Read more
UUID uses java.security.SecureRandom, which is supposed to be “cryptographically strong”. While the actual implementation is not specified and can vary between JVMs (meaning that any concrete statements made are valid only for one specific JVM), it does mandate that the output must pass a statistical random number generator test. It’s always possible for an implementation … Read more
Currently, UUID’s are as specified in RFC4122. An often neglected edge case is the NIL UUID, noted here. The following regex takes this into account and will return a match for a NIL UUID. See below for a UUID which only accepts non-NIL UUIDs. Both of these solutions are for versions 1 to 5 (see … Read more
There are two different ways of generating a UUID. If you just need a unique ID, you want a version 1 or version 4. Version 1: This generates a unique ID based on a network card MAC address and current time. If any of these things is sensitive in any way, don’t use this. The … Read more
uuid-ossp is a contrib module, so it isn’t loaded into the server by default. You must load it into your database to use it. For modern PostgreSQL versions (9.1 and newer) that’s easy: CREATE EXTENSION IF NOT EXISTS “uuid-ossp”; but for 9.0 and below you must instead run the SQL script to load the extension. … Read more
Very safe: the annual risk of a given person being hit by a meteorite is estimated to be one chance in 17 billion, which means the probability is about 0.00000000006 (6 × 10−11), equivalent to the odds of creating a few tens of trillions of UUIDs in a year and having one duplicate. In other … Read more
The uuid module provides immutable UUID objects (the UUID class) and the functions uuid1(), uuid3(), uuid4(), uuid5() for generating version 1, 3, 4, and 5 UUIDs as specified in RFC 4122. If all you want is a unique ID, you should probably call uuid1() or uuid4(). Note that uuid1() may compromise privacy since it creates … Read more
The simple answer is: **no difference, they are the same thing. 2020-08-20 Update: While GUIDs (as used by Microsoft) and UUIDs (as defined by RFC4122) look similar and serve similar purposes, there are subtle-but-occasionally-important differences. Specifically, some Microsoft GUID docs allow GUIDs to contain any hex digit in any position, while RFC4122 requires certain values … Read more