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Functions for generating UUIDv6 and UUIDv7 on PostgreSQL
/*
* 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 (UUIDv6).
*
* Referencies:
* - https://github.com/uuid6/uuid6-ietf-draft
* - https://github.com/ietf-wg-uuidrev/rfc4122bis
*
* MIT License.
*
* Tags: uuid guid uuid-generator guid-generator generator time order rfc4122 rfc-4122
*/
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 $$
declare
v_time numeric := null;
v_gregorian_t numeric := null;
v_clock_sequence_and_node numeric := null;
v_gregorian_t_hex_a varchar := null;
v_gregorian_t_hex_b varchar := null;
v_clock_sequence_and_node_hex varchar := null;
v_output_bytes bytea := null;
c_100ns_factor numeric := 10^7::numeric;
c_epoch numeric := -12219292800::numeric; -- RFC-4122 epoch: '1582-10-15'
c_version bit(64) := x'0000000000006000'; -- RFC-4122 version: b'0110...'
c_variant bit(64) := x'8000000000000000'; -- RFC-4122 variant: b'10xx...'
begin
v_time := extract(epoch from p_timestamp);
v_gregorian_t := (v_time - c_epoch) * c_100ns_factor;
v_clock_sequence_and_node := random()::numeric * 2^62::numeric;
v_gregorian_t_hex_a := lpad(to_hex((div(v_gregorian_t, 2^12::numeric)::bigint)), 12, '0');
v_gregorian_t_hex_b := lpad(to_hex((mod(v_gregorian_t, 2^12::numeric)::bigint::bit(64) | c_version)::bigint), 4, '0');
v_clock_sequence_and_node_hex := lpad(to_hex((v_clock_sequence_and_node::bigint::bit(64) | c_variant)::bigint), 16, '0');
v_output_bytes := decode(v_gregorian_t_hex_a || v_gregorian_t_hex_b || v_clock_sequence_and_node_hex, 'hex');
return encode(v_output_bytes, 'hex')::uuid;
end $$ 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, 10))
-- 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}$');
--
/*
* 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 with Unix Epoch UUID (UUIDv7).
*
* Referencies:
* - https://github.com/uuid6/uuid6-ietf-draft
* - https://github.com/ietf-wg-uuidrev/rfc4122bis
*
* MIT License.
*
* Tags: uuid guid uuid-generator guid-generator generator time order rfc4122 rfc-4122
*/
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 $$
declare
v_time numeric := null;
v_unix_t numeric := null;
v_rand_a numeric := null;
v_rand_b numeric := null;
v_unix_t_hex varchar := null;
v_rand_a_hex varchar := null;
v_rand_b_hex varchar := null;
v_output_bytes bytea := null;
c_milli_factor numeric := 10^3::numeric; -- 1000
c_micro_factor numeric := 10^6::numeric; -- 1000000
c_scale_factor numeric := 4.096::numeric; -- 4.0 * (1024 / 1000)
c_version bit(64) := x'0000000000007000'; -- RFC-4122 version: b'0111...'
c_variant bit(64) := x'8000000000000000'; -- RFC-4122 variant: b'10xx...'
begin
v_time := extract(epoch from p_timestamp);
v_unix_t := trunc(v_time * c_milli_factor);
v_rand_a := ((v_time * c_micro_factor) - (v_unix_t * c_milli_factor)) * c_scale_factor;
v_rand_b := random()::numeric * 2^62::numeric;
v_unix_t_hex := lpad(to_hex(v_unix_t::bigint), 12, '0');
v_rand_a_hex := lpad(to_hex((v_rand_a::bigint::bit(64) | c_version)::bigint), 4, '0');
v_rand_b_hex := lpad(to_hex((v_rand_b::bigint::bit(64) | c_variant)::bigint), 16, '0');
v_output_bytes := decode(v_unix_t_hex || v_rand_a_hex || v_rand_b_hex, 'hex');
return encode(v_output_bytes, 'hex')::uuid;
end $$ 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}$');
--
@productdevbook
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@fabiolimace
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fabiolimace commented Nov 7, 2023

Hi @productdevbook

The UUIDv7 generator here is in accordance with draft-14 section 5.7.

5.7.
UUIDv7 values are created by allocating a Unix timestamp in milliseconds in the most significant 48 bits and filling the remaining 74 bits, excluding the required version and variant bits, with random bits for each new UUIDv7 generated to provide uniqueness as per Section 6.9. Alternatively, implementations MAY fill the 74 bits, jointly, with a combination of the following subfields, in this order from the most significant bits to the least, to guarantee additional monotonicity within a millisecond:

An OPTIONAL sub-millisecond timestamp fraction (12 bits at maximum) as per Section 6.2 (Method 3).

The only exception is that the random() function is not a CSPRNG generator, as you may have noticed.

6.9.
Implementations SHOULD utilize a cryptographically secure pseudo-random number generator (CSPRNG) to provide values that are both difficult to predict ("unguessable") and have a low likelihood of collision ("unique"). The exception is when a suitable CSPRNG is unavailable in the execution environment.

You have to install pgcrypto to have access to crypto functions.

Thanks for asking.

@LuckyArdhika
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the uuid generated is not accurate, sometimes 1/10 condition

@fabiolimace
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fabiolimace commented Nov 14, 2023

Hi @LuckyArdhika

Could you show the code used to test the accuracy?

The UUID generated by the function is accurate to the millisecond.

In the test below, I changed 2 lines of the original code. At the end there is a comparison of the millisecond in the timestamp and the millisecond embedded in the UUID.

Note that there is no significant loss of accuracy. The only difference is due to the floating-point division operation of the IEEE-754 standard.

Additionally, the microsecond variable in the function is used to add extra monotonicity, it is not intended to be precise.

-- create or replace function uuid7() returns uuid as $$                   -- ## REPLACED LINE ##
create or replace function uuid7(parameter_timestamp timestamp with time zone) returns uuid as $$
declare
	v_time timestamp with time zone:= null;
	v_secs bigint := null;
	v_msec bigint := null;
	v_usec bigint := null;

	v_timestamp bigint := null;
	v_timestamp_hex varchar := null;

	v_random bigint := null;
	v_random_hex varchar := null;

	v_bytes bytea;

	c_variant bit(64):= x'8000000000000000'; -- RFC-4122 variant: b'10xx...'
begin

	-- Get seconds and micros
--	v_time := clock_timestamp();                       -- ## REPLACED LINE ##
	v_time := parameter_timestamp;
	v_secs := EXTRACT(EPOCH FROM v_time);
	v_msec := mod(EXTRACT(MILLISECONDS FROM v_time)::numeric, 10^3::numeric);
	v_usec := mod(EXTRACT(MICROSECONDS FROM v_time)::numeric, 10^3::numeric);

	-- Generate timestamp hexadecimal (and set version 7)
	v_timestamp := (((v_secs * 10^3) + v_msec)::bigint << 12) | (v_usec << 2);
	v_timestamp_hex := lpad(to_hex(v_timestamp), 16, '0');
	v_timestamp_hex := substr(v_timestamp_hex, 2, 12) || '7' || substr(v_timestamp_hex, 14, 3);

	-- Generate the random hexadecimal (and set variant b'10xx')
	v_random := ((random()::numeric * 2^62::numeric)::bigint::bit(64) | c_variant)::bigint;
	v_random_hex := lpad(to_hex(v_random), 16, '0');

	-- Concat timestemp and random hexadecimal
	v_bytes := decode(v_timestamp_hex || v_random_hex, 'hex');

	return encode(v_bytes, 'hex')::uuid;
	
end $$ language plpgsql;

create or replace function extract_timestamp(parameter_uuid uuid) returns bigint as $$
declare
	v_uuid_hex varchar := null;
	v_timestamp bigint := null;
	v_timestamp_hex varchar := null;
begin

	v_uuid_hex := replace(parameter_uuid::varchar, '-', '');
	v_timestamp_hex := substring(v_uuid_hex, 1, 12) || substring(v_uuid_hex, 14, 3);
	v_timestamp := ('x'||lpad(v_timestamp_hex,16,'0'))::bit(64)::bigint;

	return mod(v_timestamp >> 12, (10^3)::bigint);

end $$ language plpgsql;
select statement_timestamp()::varchar ts, mod(EXTRACT(MILLISECONDS from statement_timestamp())::bigint, 1000) ms_from_ts, extract_timestamp(uuid7(statement_timestamp())) ms_from_uuid;
ts ms_from_ts ms_from_uuid
2023-11-14 01:53:15.61599-03 616 616

@andnorxor
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For postgres 9.2 compatibility you need to cast the following two values explicitly:

  v_secs := EXTRACT(EPOCH FROM v_time)::bigint;
  v_usec := mod(EXTRACT(MICROSECONDS FROM v_time)::numeric, 10^6::numeric)::bigint;

Otherwise you'll get

SQL Error [22P02]: ERROR: invalid input syntax for integer: "1707596980.41937304"
  Where: PL/pgSQL function uuid7() line 20 at assignment

@fabiolimace
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Thank you, @andnorxor !

Functions updated.

@andnorxor
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Thank you for sharing your code; it truly was a lifesaver. In one of my projects I realized too late that postgresql-contrib was not installed on some legacy systems and it was nearly impossible to install it due security restrictions. But I had already based large parts of my module on UUIDs. Your function was the perfect workaround.

@fabiolimace
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fabiolimace commented Feb 13, 2024

🚨 FIXED rounding error

Extracting epoch seconds and converting them to bigint was causing rounding errors. For example, extracting the epoch seconds from the timestamp '2024-02-12 17:49:10.827009Z' should return 1707760150, but was returning 1707760151 (+1).

To fix this, you need to truncate before converting to bigint.

See the result of this query:

select EXTRACT(EPOCH FROM '2024-02-12 17:49:10.827009Z'::timestamp)                 as seconds,
       EXTRACT(EPOCH FROM '2024-02-12 17:49:10.827009Z'::timestamp)::bigint         as seconds_bigint,    -- implicitly rounded
       TRUNC(EXTRACT(EPOCH FROM '2024-02-12 17:49:10.827009Z'::timestamp))::bigint  as seconds_truncated; -- explicitly truncated
|seconds             |seconds_bigint|seconds_truncated|
|--------------------|--------------|-----------------|
|1,707,760,150.827009|1.707.760.151 |1.707.760.150    |

The rounding issue is now fixed.

Thanks, Tobias, for letting me know about this!

@fabiolimace
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fabiolimace commented Feb 13, 2024

I'm refactoring the functions. I hope they are more readable after refactoring.

@fabiolimace
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Refactored.

@productdevbook
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When will v6 become stable, is there any news about it?

@fabiolimace
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I don't know. I hope draft 14 is the last and the new RFC is finally completed.

There are no updates to the email archive:
https://mailarchive.ietf.org/arch/browse/uuidrev/

@ChrisJohnNewton
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I had to cast 2^12 as numeric to get this to work in PostgreSQL version 16.2

DIV(v_gregorian_t, 2^12::NUMERIC)
MOD(v_gregorian_t, 2^12::NUMERIC)

@diogobaeder
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Dude, fantastic job! \m/

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