ULID is a format for k-ordered distributed id generation. i.e. you can generate a random unique id with no central coordination and later be able to mostly sort the ids by the time they were generated.
If ids are generated within the same second on different instances they could be out of order within that second.
Source of this code:
| -- From https://github.com/geckoboard/pgulid/blob/d6187a00f66dca196cf5242588f87c3a7969df75/pgulid.sql | |
| -- | |
| -- pgulid is based on OK Log's Go implementation of the ULID spec | |
| -- | |
| -- https://github.com/oklog/ulid | |
| -- https://github.com/ulid/spec | |
| -- | |
| -- Copyright 2016 The Oklog Authors | |
| -- Licensed under the Apache License, Version 2.0 (the "License"); | |
| -- you may not use this file except in compliance with the License. | |
| -- You may obtain a copy of the License at | |
| -- | |
| -- http://www.apache.org/licenses/LICENSE-2.0 | |
| -- | |
| -- Unless required by applicable law or agreed to in writing, software | |
| -- distributed under the License is distributed on an "AS IS" BASIS, | |
| -- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
| -- See the License for the specific language governing permissions and | |
| -- limitations under the License. | |
| CREATE EXTENSION IF NOT EXISTS pgcrypto; | |
| CREATE FUNCTION generate_ulid_text() | |
| RETURNS TEXT | |
| AS $$ | |
| DECLARE | |
| -- Crockford's Base32 | |
| encoding BYTEA = '0123456789ABCDEFGHJKMNPQRSTVWXYZ'; | |
| timestamp BYTEA = E'\\000\\000\\000\\000\\000\\000'; | |
| output TEXT = ''; | |
| unix_time BIGINT; | |
| ulid BYTEA; | |
| BEGIN | |
| -- 6 timestamp bytes | |
| unix_time = (EXTRACT(EPOCH FROM NOW()) * 1000)::BIGINT; | |
| timestamp = SET_BYTE(timestamp, 0, (unix_time >> 40)::BIT(8)::INTEGER); | |
| timestamp = SET_BYTE(timestamp, 1, (unix_time >> 32)::BIT(8)::INTEGER); | |
| timestamp = SET_BYTE(timestamp, 2, (unix_time >> 24)::BIT(8)::INTEGER); | |
| timestamp = SET_BYTE(timestamp, 3, (unix_time >> 16)::BIT(8)::INTEGER); | |
| timestamp = SET_BYTE(timestamp, 4, (unix_time >> 8)::BIT(8)::INTEGER); | |
| timestamp = SET_BYTE(timestamp, 5, unix_time::BIT(8)::INTEGER); | |
| -- 10 entropy bytes | |
| ulid = timestamp || gen_random_bytes(10); | |
| -- Encode the timestamp | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 0) & 224) >> 5)); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 0) & 31))); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 1) & 248) >> 3)); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 1) & 7) << 2) | ((GET_BYTE(ulid, 2) & 192) >> 6))); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 2) & 62) >> 1)); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 2) & 1) << 4) | ((GET_BYTE(ulid, 3) & 240) >> 4))); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 3) & 15) << 1) | ((GET_BYTE(ulid, 4) & 128) >> 7))); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 4) & 124) >> 2)); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 4) & 3) << 3) | ((GET_BYTE(ulid, 5) & 224) >> 5))); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 5) & 31))); | |
| -- Encode the entropy | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 6) & 248) >> 3)); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 6) & 7) << 2) | ((GET_BYTE(ulid, 7) & 192) >> 6))); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 7) & 62) >> 1)); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 7) & 1) << 4) | ((GET_BYTE(ulid, 8) & 240) >> 4))); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 8) & 15) << 1) | ((GET_BYTE(ulid, 9) & 128) >> 7))); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 9) & 124) >> 2)); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 9) & 3) << 3) | ((GET_BYTE(ulid, 10) & 224) >> 5))); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 10) & 31))); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 11) & 248) >> 3)); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 11) & 7) << 2) | ((GET_BYTE(ulid, 12) & 192) >> 6))); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 12) & 62) >> 1)); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 12) & 1) << 4) | ((GET_BYTE(ulid, 13) & 240) >> 4))); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 13) & 15) << 1) | ((GET_BYTE(ulid, 14) & 128) >> 7))); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 14) & 124) >> 2)); | |
| output = output || CHR(GET_BYTE(encoding, ((GET_BYTE(ulid, 14) & 3) << 3) | ((GET_BYTE(ulid, 15) & 224) >> 5))); | |
| output = output || CHR(GET_BYTE(encoding, (GET_BYTE(ulid, 15) & 31))); | |
| RETURN output; | |
| END | |
| $$ | |
| LANGUAGE plpgsql | |
| VOLATILE; |
| -- Gets the 48-bit time part of the ULID and returns a timestamp | |
| CREATE FUNCTION ulid_to_timestamp(ulid UUID) | |
| RETURNS TIMESTAMP WITH TIME ZONE | |
| AS $$ | |
| SELECT TO_TIMESTAMP(timepart::BIT(48)::BIGINT::DOUBLE PRECISION / 1000.0) | |
| FROM ( | |
| SELECT ('x' || lpad((substring (u from 1 for 8) || substring (u from 10 for 4)), 12, '0')) AS timepart | |
| FROM (values (ulid::TEXT)) s (u) | |
| ) s; | |
| $$ | |
| LANGUAGE sql | |
| IMMUTABLE; |
| -- Modified from https://github.com/geckoboard/pgulid/blob/d6187a00f66dca196cf5242588f87c3a7969df75/pgulid.sql | |
| -- Returns a `uuid` type with the contents of the ULID | |
| -- | |
| -- pgulid is based on OK Log's Go implementation of the ULID spec | |
| -- | |
| -- https://github.com/oklog/ulid | |
| -- https://github.com/ulid/spec | |
| -- | |
| -- Copyright 2016 The Oklog Authors | |
| -- Licensed under the Apache License, Version 2.0 (the "License"); | |
| -- you may not use this file except in compliance with the License. | |
| -- You may obtain a copy of the License at | |
| -- | |
| -- http://www.apache.org/licenses/LICENSE-2.0 | |
| -- | |
| -- Unless required by applicable law or agreed to in writing, software | |
| -- distributed under the License is distributed on an "AS IS" BASIS, | |
| -- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
| -- See the License for the specific language governing permissions and | |
| -- limitations under the License. | |
| CREATE EXTENSION IF NOT EXISTS pgcrypto; | |
| CREATE FUNCTION generate_ulid_uuid() | |
| RETURNS UUID | |
| AS $$ | |
| DECLARE | |
| timestamp BYTEA = E'\\000\\000\\000\\000\\000\\000'; | |
| unix_time BIGINT; | |
| ulid BYTEA; | |
| BEGIN | |
| -- 6 timestamp bytes | |
| unix_time = (EXTRACT(EPOCH FROM NOW()) * 1000)::BIGINT; | |
| timestamp = SET_BYTE(timestamp, 0, (unix_time >> 40)::BIT(8)::INTEGER); | |
| timestamp = SET_BYTE(timestamp, 1, (unix_time >> 32)::BIT(8)::INTEGER); | |
| timestamp = SET_BYTE(timestamp, 2, (unix_time >> 24)::BIT(8)::INTEGER); | |
| timestamp = SET_BYTE(timestamp, 3, (unix_time >> 16)::BIT(8)::INTEGER); | |
| timestamp = SET_BYTE(timestamp, 4, (unix_time >> 8)::BIT(8)::INTEGER); | |
| timestamp = SET_BYTE(timestamp, 5, unix_time::BIT(8)::INTEGER); | |
| -- 10 entropy bytes | |
| ulid = timestamp || gen_random_bytes(10); | |
| RETURN CAST( substring(CAST (ulid AS text) from 3) AS uuid); | |
| END | |
| $$ | |
| LANGUAGE plpgsql | |
| VOLATILE; |