ydb/library/cpp/timezone_conversion/convert.cpp, branch CLI_2.32.0Mirror of YDB github reposhttps://code.mastervirt.ru/ydb/atom?h=CLI_2.32.02026-06-16T20:54:42ZSpeed up working with timezones2026-06-16T20:54:42Zshamteevshamteev@yandex-team.com2026-06-16T20:27:30Zurn:sha1:9c0feecb216b98e6e483257cf2b2afafcd7d7c77
Optimize timezone-aware query functions (timestamp_floor\_\*\_tz, format_timestamp_tz)
Problem: queries using timezone functions on a non-Moscow/non-UTC zone (e.g.
Europe/Bucharest) ran 10-20x slower than their non-timezone equivalents. For
Moscow/UTC a lookup table handles the conversion; for any other zone the code
falls back to live cctz calls.
Cause, confirmed by flamegraph and code:
1. NDatetime::ToCivilTime performed two independent timezone lookups per call.
cctz::convert(tp, tz) is defined as tz.lookup(tp).cs, and the function then
called tz.lookup(tp) again for the offset/is_dst fields. Both pieces of data
are already present in a single absolute_lookup result.
2. TimestampFloorDayTZInternal (and Month/Quarter/Year variants) located the
start of the period via a binary search that called ToCivilTime on every
iteration — \~18 iterations for the day case. Combined with (1) that is \~38
cctz lookups per call, and timestamp_floor_day_tz appears twice per row in a
typical WHERE clause.
* Changelog entry
Type: fix
1. ToCivilTime now does a single tz.lookup(tp) and reuses both cs and the
offset/is_dst fields. Behavior is identical; affects all callers.
2. TimestampFloor\{Day,Month,Quarter,Year\}TZ compute the period start directly
(subtract the civil time-of-day, or build the first second of the period and
convert it back), then verify the result. The binary search is kept as a
fallback for the rare days that do not start at midnight (DST transitions at
00:00, historical offset shifts), so results are unchanged.
commit_hash:295ee82832ab2a4a35920067e7c063d6992bb083
Restoring authorship annotation for <petrk@yandex-team.ru>. Commit 2 of 2.2022-02-10T13:47:26Zpetrkpetrk@yandex-team.ru2022-02-10T13:47:26Zurn:sha1:1fe4b402b38f476dbe36f650c3049c92ae496d38Restoring authorship annotation for <petrk@yandex-team.ru>. Commit 1 of 2.2022-02-10T13:47:26Zpetrkpetrk@yandex-team.ru2022-02-10T13:47:26Zurn:sha1:af66956edf116b93d5a07894ccb61dd4447d0b34Restoring authorship annotation for Ivan Komarov <Ivan.Komarov@dfyz.info>. Commit 2 of 2.2022-02-10T13:46:49ZIvan KomarovIvan.Komarov@dfyz.info2022-02-10T13:46:49Zurn:sha1:59aca5c5180c31691884667783dc966eb99d743aRestoring authorship annotation for Ivan Komarov <Ivan.Komarov@dfyz.info>. Commit 1 of 2.2022-02-10T13:46:48ZIvan KomarovIvan.Komarov@dfyz.info2022-02-10T13:46:48Zurn:sha1:4de97ab2fe437cbe83e4c63234e809ddd5ac34f2Restoring authorship annotation for Vlad Yaroslavlev <vladon@vladon.com>. Commit 2 of 2.2022-02-10T13:46:25ZVlad Yaroslavlevvladon@vladon.com2022-02-10T13:46:25Zurn:sha1:344ea37b4a345701ab0e67de2266a1c1bd7baf2dRestoring authorship annotation for Vlad Yaroslavlev <vladon@vladon.com>. Commit 1 of 2.2022-02-10T13:46:23ZVlad Yaroslavlevvladon@vladon.com2022-02-10T13:46:23Zurn:sha1:706b83ed7de5a473436620367af31fc0ceecde07Restoring authorship annotation for Anton Samokhvalov <pg83@yandex.ru>. Commit 2 of 2.2022-02-10T13:45:17ZAnton Samokhvalovpg83@yandex.ru2022-02-10T13:45:17Zurn:sha1:d3a398281c6fd1d3672036cb2d63f842d2cb28c5Restoring authorship annotation for Anton Samokhvalov <pg83@yandex.ru>. Commit 1 of 2.2022-02-10T13:45:15ZAnton Samokhvalovpg83@yandex.ru2022-02-10T13:45:15Zurn:sha1:72cb13b4aff9bc9cf22e49251bc8fd143f82538fRestoring authorship annotation for <orivej@yandex-team.ru>. Commit 2 of 2.2022-02-10T13:45:01Zorivejorivej@yandex-team.ru2022-02-10T13:45:01Zurn:sha1:2d37894b1b037cf24231090eda8589bbb44fb6fc