pgulid.sql

-- https://github.com/geckoboard/pgulid
-- 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;

drop function if exists gen_random_ulid;

create function gen_random_ulid() 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;