我想从版本1 UUID中提取时间戳,尝试了以下方法:
SELECT '3efe0a20-f1b3-11e3-bb44-14109fec739e'::uuid::timestamp;
这里有一个快速的示例,展示了如何在Go中提取时间,但我希望PostgreSQL有内置的方法,而不是创建一个单独的PL/pgSql函数:
http://play.golang.org/p/XRCooLgfaG
我想从版本1 UUID中提取时间戳,尝试了以下方法:
SELECT '3efe0a20-f1b3-11e3-bb44-14109fec739e'::uuid::timestamp;
这里有一个快速的示例,展示了如何在Go中提取时间,但我希望PostgreSQL有内置的方法,而不是创建一个单独的PL/pgSql函数:
http://play.golang.org/p/XRCooLgfaG
我已经使用来自我的数据库的UUID进行了测试,似乎即使没有无符号大整数,它也能很好地运行。
CREATE FUNCTION uuid_timestamp(id uuid) RETURNS timestamptz AS $$
select TIMESTAMP WITH TIME ZONE 'epoch' +
(((('x' || lpad(split_part(id::text, '-', 1), 16, '0'))::bit(64)::bigint) +
(('x' || lpad(split_part(id::text, '-', 2), 16, '0'))::bit(64)::bigint << 32) +
((('x' || lpad(split_part(id::text, '-', 3), 16, '0'))::bit(64)::bigint&4095) << 48) - 122192928000000000) / 10000000 ) * INTERVAL '1 second';
$$ LANGUAGE SQL
IMMUTABLE
RETURNS NULL ON NULL INPUT;
我在2099年创造的一个V1 uuid!
select uuid_timestamp('6d248400-65b7-1243-a57a-14109fec739e');
uuid_timestamp
------------------------
2099-08-01 11:30:00-07
(1 row)
根据我们的测试,与@Krut实现相比较快的一种替代方案:
CREATE OR REPLACE FUNCTION uuid_timestamp(uuid UUID) RETURNS TIMESTAMPTZ AS $$
DECLARE
bytes bytea;
BEGIN
bytes := uuid_send(uuid);
RETURN to_timestamp(
(
(
(get_byte(bytes, 0)::bigint << 24) |
(get_byte(bytes, 1)::bigint << 16) |
(get_byte(bytes, 2)::bigint << 8) |
(get_byte(bytes, 3)::bigint << 0)
) + (
((get_byte(bytes, 4)::bigint << 8 |
get_byte(bytes, 5)::bigint)) << 32
) + (
(((get_byte(bytes, 6)::bigint & 15) << 8 | get_byte(bytes, 7)::bigint) & 4095) << 48
) - 122192928000000000
) / 10000 / 1000::double precision
);
END
$$ LANGUAGE plpgsql
IMMUTABLE PARALLEL SAFE
RETURNS NULL ON NULL INPUT;
=> select uuid_timestamp(uuid_generate_v1()), now();
uuid_timestamp | now
----------------------------+-------------------------------
2020-04-29 17:40:54.519+00 | 2020-04-29 17:40:54.518204+00
(1 row)
此外,它假设输入是 v1 版本。如果您尝试使用类似 v4 的输入,则应该预期会得到奇怪的答案,或者更改函数使其在不是 v1 版本时引发错误。
=> select uuid_timestamp(uuid_generate_v4());
uuid_timestamp
----------------------------
4251-12-19 17:38:34.866+00
(1 row)
-- Build UUIDv1 via RFC 4122.
-- clock_seq is a random 14bit unsigned int with range [0,16384)
CREATE OR REPLACE FUNCTION form_uuid_v1(ts TIMESTAMPTZ, clock_seq INTEGER, mac MACADDR)
RETURNS UUID AS $$
DECLARE
t BIT(60) := (extract(EPOCH FROM ts) * 10000000 + 122192928000000000) :: BIGINT :: BIT(60);
uuid_hi BIT(64) := substring(t FROM 29 FOR 32) || substring(t FROM 13 FOR 16) || b'0001' ||
substring(t FROM 1 FOR 12);
BEGIN
RETURN lpad(to_hex(uuid_hi :: BIGINT) :: TEXT, 16, '0') ||
(to_hex((b'10' || clock_seq :: BIT(14)) :: BIT(16) :: INTEGER)) :: TEXT ||
replace(mac :: TEXT, ':', '');
END
$$ LANGUAGE plpgsql;
-- Usage
select form_uuid_v1(now(), 666, '44:88:AA:DD:BB:88');