Does this method produce UUID variant 2, version 4, according to RFC4122?Īccording to the above, yes: the Guid.NewGuid which calls internally the “UuidCreate”API is compliant with RFC 4122, variant 2, version 4.We can also have a call regarding the mentioned issue.įrom our source code I can see that the following modifications are done on the GUID: If you have any questions or concerns, please let me know. The Microsoft Implementation also uses the random guid (Variant 2, Version 4)version of RFC 4122.įor the moment I am double checking the UuidCreate function to verify that it applies to the mentioned version of the RFC. NET Source Source Code for the Guid.NewGuid static API:Īccording to this source code the GUID is generated using the I have done a research regarding the Guid.NewGuid generation and I have gone through the following articles and blogs so far: You may reach me using the contact information listed below, referencing the SR number 118090418920099. I am the Support Professional who will be working with you on this Service Request. The number collisions in both scenarios tends to increase as number of rows grows.Thank you for contacting Microsoft Support. The sum of collisions after 40 million rows with each function is: +-+-+ When a collision is found, the row is updated incrementing collisions column: INSERT INTO test (uuid) VALUES (uuid_v4()) ON DUPLICATE KEY UPDATE collisions=collisions+1 I've created following test scenario: Insert random UUID v4 as primary key for a table until 40.000.000 rows are created. NOTE: Unfortunately MariaDB doesn't support RANDOM_BYTES() (See ) Test RETURN '-', '-4', '-', '-', should generate UUID V4 random enough to don't care about collisions. 4th block first nibble can only be 8, 9 A or B, remaining is random SET = SUBSTR(HEX(RANDOM_BYTES(2)), 2, 3) 3th block will start with a 4 indicating the version, remaining is random 1th and 2nd block are made of 6 random bytes So we can update the function to: CREATE FUNCTION uuid_v4s() This function returns a binary string of len random bytes generated using the random number generator of the SSL library. It's possible to generate safe UUID V4 on MySQL side using random_bytes() function: In the practice, this mean that the generated UUID using this function might (and will) be biased, and collisions can occur more frequently then expected. It is a fast way to generate random numbers on demand that is portable between platforms for the same MySQL version. RAND() is not meant to be a perfect random generator. LPAD(HEX(FLOOR(RAND() * 0xffff)), 4, '0'))) īoth existing answers relies on MySQL RAND() function: In the off chance you're working with a DB and don't have perms to create functions, here's the same version as above that works just as a SQL expression: SELECT LOWER(CONCAT( Note: The pseudo-random number generation used (MySQL's RAND) is notĬryptographically secure and thus has some bias which can increase the collision RETURN '-', '-', '-', '-', Switch back the delimiter 5th section first half-byte can only be 8, 9 A or B 4th section will start with a 4 indicating the version Generate 8 2-byte strings that we will combine into a UUIDv4 Change delimiter so that the function body doesn't end the function declaration I'm answering my own question to share that in the hope that it'll be Mysql function that generates a random UUID (i.e. I've spent quite some time looking for a solution and came up with the following
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