Use the pairing heap instead of a flat array for LSN replay waiters 06c418e163 introduced pg_wal_replay_wait() procedure allowing to wait for the particular LSN to be replayed on standby. The waiters were stored in the flat array. Even though scanning small arrays is fast, that might be a problem at scale (a lot of waiting processes).
This commit replaces the flat shared memory array with the pairing heap, which holds the waiter with the least LSN at the top. This gives us O(log N) complexity for both inserting and removing waiters. Reported-by: Alvaro Herrera Discussion: https://postgr.es/m/202404030658.hhj3vfxeyhft%40alvherre.pgsql Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/bf1e65080629e2b0ac47ffe245576da96eff8420 Modified Files -------------- src/backend/access/transam/xlogrecovery.c | 2 +- src/backend/commands/waitlsn.c | 168 ++++++++++++++---------------- src/backend/lib/pairingheap.c | 18 +++- src/include/commands/waitlsn.h | 44 +++++++- src/include/lib/pairingheap.h | 3 + 5 files changed, 140 insertions(+), 95 deletions(-)
