Functions for generating UUIDv6 and UUIDv7 on PostgreSQL

UUIDv6.sql

/*
 * MIT License
 *
 * Copyright (c) 2023-2024 Fabio Lima
 * 
 *  Permission is hereby granted, free of charge, to any person obtaining a copy
 *  of this software and associated documentation files (the "Software"), to deal
 *  in the Software without restriction, including without limitation the rights
 *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 *  copies of the Software, and to permit persons to whom the Software is
 *  furnished to do so, subject to the following conditions:
 * 
 *  The above copyright notice and this permission notice shall be included in
 *  all copies or substantial portions of the Software.
 * 
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 *  THE SOFTWARE.
 */
 
/**
 * Returns a time-ordered UUID with Gregorian Epoch (UUIDv6).
 *
 * Referencie: https://www.rfc-editor.org/rfc/rfc9562.html
 *
 * MIT License.
 *
 */
create or replace function uuid6() returns uuid as $$
declare
begin
	return uuid6(clock_timestamp());
end $$ language plpgsql;

create or replace function uuid6(p_timestamp timestamp with time zone) returns uuid as $$
declare

	v_time double precision := null;

	v_gregorian_t bigint := null;
	v_clock_sequence_and_node bigint := null;

	v_gregorian_t_hex_a varchar := null;
	v_gregorian_t_hex_b varchar := null;
	v_clock_sequence_and_node_hex varchar := null;

	c_epoch double precision := 12219292800; -- RFC-9562 epoch: 1582-10-15
	c_100ns_factor double precision := 10^7; -- RFC-9562 precision: 100 ns

	c_version bigint := x'0000000000006000'::bigint; -- RFC-9562 version: b'0110...'
	c_variant bigint := x'8000000000000000'::bigint; -- RFC-9562 variant: b'10xx...'

begin

	v_time := extract(epoch from p_timestamp);

	v_gregorian_t := trunc((v_time + c_epoch) * c_100ns_factor);
	v_clock_sequence_and_node := trunc(random() * 2^30)::bigint << 32 | trunc(random() * 2^32)::bigint;

	v_gregorian_t_hex_a := lpad(to_hex((v_gregorian_t >> 12)), 12, '0');
	v_gregorian_t_hex_b := lpad(to_hex((v_gregorian_t & 4095) | c_version), 4, '0');
	v_clock_sequence_and_node_hex := lpad(to_hex(v_clock_sequence_and_node | c_variant), 16, '0');

	return (v_gregorian_t_hex_a || v_gregorian_t_hex_b  || v_clock_sequence_and_node_hex)::uuid;

end $$ language plpgsql;

-------------------------------------------------------------------
-- EXAMPLE:
-------------------------------------------------------------------
-- 
-- select uuid6() uuid, clock_timestamp()-statement_timestamp() time_taken;
--
-- |uuid                                  |time_taken        |
-- |--------------------------------------|------------------|
-- |1eeca632-cf2a-65e0-85f3-151064c2409d  |00:00:00.000108   |
-- 

-------------------------------------------------------------------
-- EXAMPLE: generate a list
-------------------------------------------------------------------
-- 
-- with x as (select clock_timestamp() as t from generate_series(1, 1000))
-- select uuid6(x.t) uuid, x.t::text ts from x;
-- 
-- |uuid                                |ts                           |
-- |------------------------------------|-----------------------------|
-- |1eeca634-f783-63f0-9988-48906d79f782|2024-02-13 08:30:37.891480-03|
-- |1eeca634-f783-6c24-97af-605238f4c3d0|2024-02-13 08:30:37.891691-03|
-- |1eeca634-f783-6e7c-9c2e-624f24b87738|2024-02-13 08:30:37.891754-03|
-- |1eeca634-f784-6070-a67b-4fc6659143e7|2024-02-13 08:30:37.891800-03|
-- |1eeca634-f784-6200-befd-0e20be5b0087|2024-02-13 08:30:37.891842-03|
-- |1eeca634-f784-6390-8f79-d4dacec1c3e0|2024-02-13 08:30:37.891881-03|
-- |1eeca634-f784-6520-8ee7-96091b017d4c|2024-02-13 08:30:37.891920-03|
-- |1eeca634-f784-66b0-a63e-c285d8a63e21|2024-02-13 08:30:37.891958-03|
-- |1eeca634-f784-6840-8c00-38659c4bf807|2024-02-13 08:30:37.891997-03|
-- |1eeca634-f784-69d0-b775-4bbfd45eb99e|2024-02-13 08:30:37.892036-03|
-- 

-------------------------------------------------------------------
-- FOR TEST: the expected result is an empty result set
-------------------------------------------------------------------
-- 
-- with t as (select uuid6() as id from generate_series(1, 1000))
-- select * from t where (id is null or id::text !~ '^[a-f0-9]{8}-[a-f0-9]{4}-6[a-f0-9]{3}-[89ab][a-f0-9]{3}-[a-f0-9]{12}$');
--

UUIDv7.sql

/*
 * MIT License
 *
 * Copyright (c) 2023-2024 Fabio Lima
 * 
 *  Permission is hereby granted, free of charge, to any person obtaining a copy
 *  of this software and associated documentation files (the "Software"), to deal
 *  in the Software without restriction, including without limitation the rights
 *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 *  copies of the Software, and to permit persons to whom the Software is
 *  furnished to do so, subject to the following conditions:
 * 
 *  The above copyright notice and this permission notice shall be included in
 *  all copies or substantial portions of the Software.
 * 
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 *  THE SOFTWARE.
 */
 
/**
 * Returns a time-ordered UUID with Unix Epoch (UUIDv7).
 * 
 * Referencie: https://www.rfc-editor.org/rfc/rfc9562.html
 *
 * MIT License.
 *
 */
create or replace function uuid7() returns uuid as $$
declare
begin
	return uuid7(clock_timestamp());
end $$ language plpgsql;

create or replace function uuid7(p_timestamp timestamp with time zone) returns uuid as $$
declare

	v_time double precision := null;

	v_unix_t bigint := null;
	v_rand_a bigint := null;
	v_rand_b bigint := null;

	v_unix_t_hex varchar := null;
	v_rand_a_hex varchar := null;
	v_rand_b_hex varchar := null;

	c_milli double precision := 10^3;  -- 1 000
	c_micro double precision := 10^6;  -- 1 000 000
	c_scale double precision := 4.096; -- 4.0 * (1024 / 1000)
	
	c_version bigint := x'0000000000007000'::bigint; -- RFC-9562 version: b'0111...'
	c_variant bigint := x'8000000000000000'::bigint; -- RFC-9562 variant: b'10xx...'

begin

	v_time := extract(epoch from p_timestamp);

	v_unix_t := trunc(v_time * c_milli);
	v_rand_a := trunc((v_time * c_micro - v_unix_t * c_milli) * c_scale);
	v_rand_b := trunc(random() * 2^30)::bigint << 32 | trunc(random() * 2^32)::bigint;

	v_unix_t_hex := lpad(to_hex(v_unix_t), 12, '0');
	v_rand_a_hex := lpad(to_hex((v_rand_a | c_version)::bigint), 4, '0');
	v_rand_b_hex := lpad(to_hex((v_rand_b | c_variant)::bigint), 16, '0');

	return (v_unix_t_hex || v_rand_a_hex || v_rand_b_hex)::uuid;
	
end $$ language plpgsql;
-------------------------------------------------------------------
-- EXAMPLE:
-------------------------------------------------------------------
-- 
-- select uuid7() uuid, clock_timestamp()-statement_timestamp() time_taken;
--
-- |uuid                                  |time_taken        |
-- |--------------------------------------|------------------|
-- |018da240-e0db-72e1-86f5-345c2c240387  |00:00:00.000222   |
-- 

-------------------------------------------------------------------
-- EXAMPLE: generate a list
-------------------------------------------------------------------
-- 
-- with x as (select clock_timestamp() as t from generate_series(1, 1000))
-- select uuid7(x.t) uuid, x.t::text ts from x;
-- 
-- |uuid                                |ts                           |
-- |------------------------------------|-----------------------------|
-- |018da235-6271-70cd-a937-0bb7d22b801e|2024-02-13 08:23:44.113054-03|
-- |018da235-6271-7214-9188-1d3191883b5d|2024-02-13 08:23:44.113126-03|
-- |018da235-6271-723d-bebe-87f66085fad7|2024-02-13 08:23:44.113143-03|
-- |018da235-6271-728f-86ba-6e277d10c0a3|2024-02-13 08:23:44.113156-03|
-- |018da235-6271-72b8-9887-f31e4ca48020|2024-02-13 08:23:44.113168-03|
-- |018da235-6271-72e1-bbeb-8b686d0d4281|2024-02-13 08:23:44.113179-03|
-- |018da235-6271-730a-96a2-73275626f72a|2024-02-13 08:23:44.113190-03|
-- |018da235-6271-7333-8a5c-9d1ab89dc489|2024-02-13 08:23:44.113201-03|
-- |018da235-6271-735c-ba64-a42b55ad7d5c|2024-02-13 08:23:44.113212-03|
-- |018da235-6271-7385-a0fb-c65f5be24073|2024-02-13 08:23:44.113223-03|
--

-------------------------------------------------------------------
-- FOR TEST: the expected result is an empty result set
-------------------------------------------------------------------
-- 
-- with t as (select uuid7() as id from generate_series(1, 1000))
-- select * from t where (id is null or id::text !~ '^[a-f0-9]{8}-[a-f0-9]{4}-7[a-f0-9]{3}-[89ab][a-f0-9]{3}-[a-f0-9]{12}$');
--

v_rand_b := random()::numeric * 2^62::numeric;

This line wants to produce 62 random bits, but a double between 0 and 1 only has 52 bits in the mantissa. Casting it to numeric doesn't give you more bits of entropy.

You need to do something like:

-- Generate a random 64-bit integer
create or replace function random_bigint() returns bigint as $$
declare
    hi bigint;
    lo bigint;
begin
    -- generate a number from 0 to 4294967295 inclusive
    hi := (random() * 0x100000000)::bigint;
    lo := (random() * 0x100000000)::bigint;
    return (hi << 32) | lo;
end;
$$ language plpgsql;

You are right @eloff. I missed the mantissa detail.

Replaced all numeric data types with bigint or double precision. I was using numeric to resist IEEE 754 floating point arithmetic, but this resistance is futile.

Here are the diff lines related to the variable v_rand_b:

- 	v_rand_b := random()::numeric * 2^62::numeric;
+ 	v_rand_b := trunc(random() * 2^30)::bigint << 32 | trunc(random() * 2^32)::bigint;

I think the functions are simpler now (and maybe faster).

Thank you for letting me know! 👍