PostgreSQL generate unique sorted IDs for timestamps

snowflake.sql

-- taken from https://rob.conery.io/2014/05/28/a-better-id-generator-for-postgresql/

create schema idgen;
create sequence idgen.global_id_sequence;

CREATE OR REPLACE FUNCTION idgen.id_generator(
    myts timestamp, 
    OUT result bigint) AS $$
DECLARE
    our_epoch bigint := 1314220021721;
    seq_id bigint;
    now_millis bigint;
    -- the id of this DB shard, must be set for each
    -- schema shard you have - you could pass this as a parameter too
    shard_id int := 1;
BEGIN
    SELECT nextval('idgen.global_id_sequence') % 1024 INTO seq_id;

    SELECT FLOOR(EXTRACT(EPOCH FROM myts) * 1000) INTO now_millis;
    result := (now_millis - our_epoch) << 23;
    result := result | (shard_id << 10);
    result := result | (seq_id);
END;
$$ LANGUAGE PLPGSQL;

ulid.sql

CREATE EXTENSION IF NOT EXISTS pgcrypto;

-- Based roughly on: https://github.com/oklog/ulid
CREATE OR REPLACE FUNCTION generate_ulid(myts timestamp)
RETURNS TEXT
AS $$
DECLARE
  -- Crockford's Base32
  encoding   BYTEA = '0123456789ABCDEFGHJKMNPQRSTVWXYZ';
  timestamp  BYTEA = '\\000\\000\\000\\000\\000\\000';
  output     TEXT = '';
  unix_time  BIGINT;
  ulid       BYTEA;
BEGIN
  -- 6 timestamp bytes
  unix_time = (EXTRACT(EPOCH FROM myts) * 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;