These two pieces of information are converted to a UUID using the SHA1 hashing algorithm.Īn important point to note is UUID v5 is consistent. Namespace: A fixed UUID used in combination with the input string to differentiate between UUIDs generated in different applications, and to prevent rainbow table hacks.Input string: Any string that can change in your application.Unlike v1 or v4, UUID v5 is generated by providing two pieces of input information: If you want a unique ID that’s not random, UUID v5 could be the right choice. If your application is mission critical (for example, bank transactions or medical systems), you should still add a uniqueness constraint to avoid UUIDv4 collision V5: Non-Random UUIDs # With the sheer number of possible combinations (2^128), it would be almost impossible to generate a duplicate unless you are generating trillions of IDs every second, for many years. The question is, do you need to worry about it? However, there is now a chance that a UUID could be duplicated. Because of this, there is no way to identify information about the source by looking at the UUID. The bits that comprise a UUID v4 are generated randomly and with no inherent logic. The generation of a v4 UUID is much simpler to comprehend. Try regenerating the UUIDs above, and you will see that some part of the UUID v1 is constant. Because UUID v1 takes the time and your MAC address into consideration, this also means that someone could potentially identify the time and place(i.e. This guaranteed uniqueness comes at the cost of anonymity. In that case, the chance of collision changes from impossible to very very small because of the random bits. This means you are guaranteed to get a completely unique ID, unless you generate it from the same computer, and at the exact same time. In addition to this, it also introduces another random component just to be sure of its uniqueness. UUID v1 is generated by using a combination the host computers MAC address and the current date and time. We’ll talk about v5 later V1 : Uniqueness # UUIDs are just 128 bit pieces of data, that is displayed as (128/4) = 32 hexadecimal digits, like this : ba6eb330-4f7f-11eb-a2fb-67c34e9ac07cĪt first glance UUID v1 and v4 look the same, but try regenerating them and the difference will be more apparent. This is a tradeoff between uniqueness and randomness, and something that the different UUID versions solve in different ways. How do you ensure that there is just one copy of the identifier you made, and no more? And even then, how do you make sure that there is no correlation between any two identifiers? However, ensuring uniqueness is a challenge in itself. UUIDs address the problem of generating a unique ID - either randomly, or using some data as a seed. The “Universally unique identifier”, or UUID, was designed to provide a consistent format for any unique ID we use for our data. Having a unique identifier is an important requirement in many applications today. We will go through their implementation and differences, and when you should use them. Since the performance difference between Rust-based UUID generation and Ecto.This post will describe UUID v1, v4, and v5, with examples. Though you may have to add Process.sleep(1) between the generations to skip one millisecond (UUIDv7 is based on milliseconds and ends with random bits) You can verify the UUIDs are ordered by running a small test: uuid1 = UUIDv7.generate() It’s easy to set up, you only have to change one line: def do NIFs are precompiled and generated for most platforms. The new library is called UUIDv7 and is available on Hex UUIDv7 - Hex.īecause it’s based on Rust, the UUID generation is a whopping 72% faster than the default Ecto.UUID version 4 generator. So I decided to build one based on a Rust package, which is relatively mature. My favourite is UUIDv7 because they’re like UUIDv4 but the first characters are based on a millisecond timestamp it seems like a very small change.Įlixir doesn’t have a common implementation of UUIDv7 yet, and Ecto is based on UUIDv4. I especially liked this post that analyzes the new standards: UUIDv6, UUIDv7 and UUIDv8 are new standards to deal with issues found in UUIDv4 and earlier. They’re nice at first but then you have to index and order by a different field like created_at, while serial and bigserial already have an order and are indexed as the primary key. Recently, some of my colleagues talked about database ids and uuids and their problems, and I remembered the pain of working with randomly distributed primary keys.
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