Use cases for UUIDs (v4 and other)

[ctavan]

A collection of real-world use cases of UUIDs other than random v4 UUIDs:

• Specs:
  • UUIDs are required by the W3C File API: https://www.w3.org/TR/FileAPI/#url (The spec explicitly references RFC4122 however Example 8 in the spec provides an invalid UUID: blob:https://example.org/9115d58c-bcda-ff47-86e5-083e9a2153041).
• Databases:
  • MySQL: https://mysqlserverteam.com/mysql-8-0-uuid-support/
  • MySQL (reference): https://dev.mysql.com/doc/refman/8.0/en/miscellaneous-functions.html#function_uuid
  • SQL Server: https://docs.microsoft.com/en-us/sql/t-sql/functions/newsequentialid-transact-sql?view=sql-server-2017
  • PostgreSQL: https://www.postgresql.org/docs/12/uuid-ossp.html
  • Cassandra: https://docs.datastax.com/en/dse/6.7/cql/cql/cql_using/refTimeUuidFunctions.html

Google Cloud Spanner explicitly advises NOT to use v1 UUIDs: https://cloud.google.com/spanner/docs/schema-and-data-model#choosing_a_primary_key

Use a Universally Unique Identifier (UUID). Version 4 UUID is recommended, because it uses random values in the high-order bits. Don't use a UUID algorithm (such as version 1 UUID) that stores the timestamp in the high order bits.