Can you have two UUIDs the same?
No, a UUID can't be guaranteed to be unique. A UUID is just a 128-bit random number. When my computer generates a UUID, there's no practical way it can prevent your computer or any other device in the universe from generating that same UUID at some time in the future.
UUIDs are generally used for identifying information that needs to be unique within a system or network thereof. Their uniqueness and low probability in being repeated makes them useful for being associative keys in databases and identifiers for physical hardware within an organization.
In other words, only after generating 1 billion UUIDs every second for the next 100 years, the probability of creating just one duplicate would be about 50%. Caveat: However, these probabilities only hold when the UUIDs are generated using sufficient entropy.
32 hexadecimals x log2(16) bits/hexadecimal = 128 bits in a UUID. In the version 4, variant 1 type of UUID, 6 bits are fixed and the remaining 122 bits are randomly generated, for a total of 2¹²² possible UUIDs.
You should certainly detect if a collision occurs, and your application should throw an exception if it does happen. E.g. if the UUID is used as primary key in the database, then the database should throw an error when inserting a colliding ID.
A collision is possible but the total number of unique keys generated is so large that the possibility of a collision is almost zero. As per Wikipedia, the number of UUIDs generated to have atleast 1 collision is 2.71 quintillion. This is equivalent to generating around 1 billion UUIDs per second for about 85 years.
Pros. Using UUID for a primary key brings the following advantages: UUID values are unique across tables, databases, and even servers that allow you to merge rows from different databases or distribute databases across servers. UUID values do not expose the information about your data so they are safer to use in a URL.
A GUID is a unique number that can be used as an identifier for anything in the universe, but unlike ISBN there is no central authority - the uniqueness of a GUID relies on the algorthm that was used to generate it.
How to Generate Unique ID for the Model - YouTube
A class that represents an immutable universally unique identifier (UUID). A UUID represents a 128-bit value. There exist different variants of these global identifiers.
Which UUID should I use?
If you want a unique ID that's not random, UUID v5 could be the right choice. Unlike v1 or v4, UUID v5 is generated by providing two pieces of input information: Input string: Any string that can change in your application.
By using UUIDs, you ensure that your ID is not just unique in the context of a single database table or web application, but is truly unique in the universe. No other ID in existence should be the same as yours.
- Power off the virtual machine whose UUID you are going to change.
- Edit the virtual machine's configuration file (. vmx ). ...
- Search the file for the line: ...
- Enter the new UUID in this format. ...
- Save and close the configuration file.
- Power on the virtual machine.
A collision is possible but the total number of unique keys generated is so large that the possibility of a collision is almost zero. As per Wikipedia, the number of UUIDs generated to have atleast 1 collision is 2.71 quintillion. This is equivalent to generating around 1 billion UUIDs per second for about 85 years.
Use encapsulation, create a UUID factory object, where you save old ones in a set, then every time check is the new UUID exist or no, then return it only if it doesn't exist, else repeat.
How does UUID work? The UUID relies on a combination of components to ensure uniqueness. UUIDs are constructed in a sequence of digits equal to 128 bits. The ID is in hexadecimal digits, meaning it uses the numbers 0 through 9 and letters A through F.
The GUID designation is an industry standard defined by Microsoft to provide a reference number which is unique in any context. UUID is a term that stands for Universal Unique Identifier. Similarly, GUID stands for Globally Unique Identifier. So basically, two terms for the same thing.
A collision is possible but the total number of unique keys generated is so large that the possibility of a collision is almost zero. As per Wikipedia, the number of UUIDs generated to have atleast 1 collision is 2.71 quintillion. This is equivalent to generating around 1 billion UUIDs per second for about 85 years.
A GUID is a unique number that can be used as an identifier for anything in the universe, but unlike ISBN there is no central authority - the uniqueness of a GUID relies on the algorthm that was used to generate it.
- Generate 16 random bytes (=128 bits)
- Adjust certain bits according to RFC 4122 section 4.4 as follows: ...
- Encode the adjusted bytes as 32 hexadecimal digits.
- Add four hyphen "-" characters to obtain blocks of 8, 4, 4, 4 and 12 hex digits.