UUID generators

These functions return native Postgres uuid values. Install into extensions before running the examples. Both functions are declared with Postgres’s default volatility (VOLATILE) and read clock_timestamp() on each call.

gen_random_uuid_v6

extensions.gen_random_uuid_v6() → uuid

Builds a UUID with a reordered timestamp based on the 1582-10-15 epoch. It sets the version nibble to 6 and the variant bits to 10, and fills the remaining clock-sequence/node portion using random().

Guarantees: returns a UUID with the version and variant bits set by the implementation. No arguments or sequence setup are needed.

Does not guarantee: unique values, a stable node identifier, cryptographic unpredictability, strict generation order or exact clock precision. The implementation rounds epoch seconds before adding microseconds; see time rounding.

select extensions.gen_random_uuid_v6();
-- A generated UUID; its third group starts with 6.

gen_random_uuid_v7

extensions.gen_random_uuid_v7() → uuid

Builds a UUID with Unix milliseconds in its leading field. The implementation places v_usec << 2 into the following field, sets the version nibble to 7 and the variant bits to 10, and obtains the trailing random portion from random().

Guarantees: returns a UUID with version 7 and the variant bits set by the implementation. It can be used directly as a uuid column default.

Does not guarantee: unique values, cryptographic unpredictability, strict time ordering or an exact creation timestamp. The additional time bits are implementation-specific; do not assume another library will interpret them the same way. Epoch seconds, milliseconds and microseconds are rounded during assignment in 0.0.4.

select extensions.gen_random_uuid_v7();
-- A generated UUID; its third group starts with 7.

For table examples, see primary keys. For UUIDv7 decoding, see timestamp extraction.