From 6890f52395a924f6af33eb86c2c3addb204ef483 Mon Sep 17 00:00:00 2001 From: Andrey Borodin Date: Fri, 31 Jan 2025 12:03:16 +0500 Subject: [PATCH v2] UUDv7: fix offset computations in dates after 2262 We used nanosecond representation of offsetted time values which cannot be stored in 64-bit integer for dates significantly after beginning of UNIX epoch. To prevent overflow we separate millisecond part from nanoseconds, thus allowing us to store both parts in 64-bit integers. --- src/backend/utils/adt/uuid.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/src/backend/utils/adt/uuid.c b/src/backend/utils/adt/uuid.c index 4f8402ef92..f579bb3a64 100644 --- a/src/backend/utils/adt/uuid.c +++ b/src/backend/utils/adt/uuid.c @@ -28,6 +28,7 @@ /* helper macros */ #define NS_PER_S INT64CONST(1000000000) #define NS_PER_MS INT64CONST(1000000) +#define US_PER_MS INT64CONST(1000) #define NS_PER_US INT64CONST(1000) /* @@ -69,6 +70,7 @@ static bool uuid_abbrev_abort(int memtupcount, SortSupport ssup); static Datum uuid_abbrev_convert(Datum original, SortSupport ssup); static inline void uuid_set_version(pg_uuid_t *uuid, unsigned char version); static inline int64 get_real_time_ns_ascending(); +static pg_uuid_t *generate_uuidv7(uint64 unix_ts_ms, uint32 ns_in_ms); Datum uuid_in(PG_FUNCTION_ARGS) @@ -523,18 +525,16 @@ get_real_time_ns_ascending() * described in the RFC. This method utilizes 12 bits from the "rand_a" bits * to store a 1/4096 (or 2^12) fraction of sub-millisecond precision. * - * ns is a number of nanoseconds since start of the UNIX epoch. This value is + * unix_ts_ms is a number of milliseconds since start of the UNIX epoch, + * ns_in_ms is a number of nanoseconds within millisecond. These values are * used for time-dependent bits of UUID. */ static pg_uuid_t * -generate_uuidv7(int64 ns) +generate_uuidv7(uint64 unix_ts_ms, uint32 ns_in_ms) { pg_uuid_t *uuid = palloc(UUID_LEN); - int64 unix_ts_ms; int32 increased_clock_precision; - unix_ts_ms = ns / NS_PER_MS; - /* Fill in time part */ uuid->data[0] = (unsigned char) (unix_ts_ms >> 40); uuid->data[1] = (unsigned char) (unix_ts_ms >> 32); @@ -547,7 +547,7 @@ generate_uuidv7(int64 ns) * sub-millisecond timestamp fraction (SUBMS_BITS bits, not * SUBMS_MINIMAL_STEP_BITS) */ - increased_clock_precision = ((ns % NS_PER_MS) * (1 << SUBMS_BITS)) / NS_PER_MS; + increased_clock_precision = ((ns_in_ms) * (1 << SUBMS_BITS)) / NS_PER_MS; /* Fill the increased clock precision to "rand_a" bits */ uuid->data[6] = (unsigned char) (increased_clock_precision >> 8); @@ -586,7 +586,8 @@ generate_uuidv7(int64 ns) Datum uuidv7(PG_FUNCTION_ARGS) { - pg_uuid_t *uuid = generate_uuidv7(get_real_time_ns_ascending()); + int64 ns = get_real_time_ns_ascending(); + pg_uuid_t *uuid = generate_uuidv7(ns / NS_PER_MS, ns % NS_PER_MS); PG_RETURN_UUID_P(uuid); } @@ -600,7 +601,9 @@ uuidv7_interval(PG_FUNCTION_ARGS) Interval *shift = PG_GETARG_INTERVAL_P(0); TimestampTz ts; pg_uuid_t *uuid; + /* 64 bits is enough for real time, but not for a time range of UUID */ int64 ns = get_real_time_ns_ascending(); + int64 us; /* * Shift the current timestamp by the given interval. To calculate time @@ -621,11 +624,10 @@ uuidv7_interval(PG_FUNCTION_ARGS) /* * Convert a TimestampTz value back to an UNIX epoch and back nanoseconds. */ - ns = (ts + (POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY * USECS_PER_SEC) - * NS_PER_US + ns % NS_PER_US; + us = (ts + (POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY * USECS_PER_SEC); /* Generate an UUIDv7 */ - uuid = generate_uuidv7(ns); + uuid = generate_uuidv7(us / US_PER_MS, (us % US_PER_MS) * NS_PER_US + ns % NS_PER_US); PG_RETURN_UUID_P(uuid); } -- 2.39.5 (Apple Git-154)