Commit trong PostgreSQL là làm những gì?

[xluffy]

In most cases, all a COMMIT has to do is

• set the two bits for the transaction in the commit log to TRANSACTION_STATUS_COMMITTED (0b01) (persisted in pg_xact)
• if track_commit_timestamp is set to on, record the commit timestamp (persisted in pg_commit_ts)
• flush the write-ahead log (WAL) (persisted in pg_wal) to disk, unless synchronous_commit is set to off

Note that because of the multi-versioning architecture of PostgreSQL, both COMMIT and ROLLBACK are normally very fast operations: they both don't have to touch the tables, they only register the status of the transaction in the commit log.

https://www.cybertec-postgresql.com/en/why-do-i-have-a-slow-commit-in-postgresql/