RE: Storage Manager (was postgres 7.2 features.)
От | Mikheev, Vadim |
---|---|
Тема | RE: Storage Manager (was postgres 7.2 features.) |
Дата | |
Msg-id | 8F4C99C66D04D4118F580090272A7A23018C55@SECTORBASE1 обсуждение исходный текст |
Список | pgsql-hackers |
> > * It's always faster than WAL in the presence of stable main memory. > > (Whether the stable caches in modern disk drives is an > > approximation I don't know). > > Yes, only if you want to be able to log changes to a txlog to > be able to rollforward changes after a restore, then that benefit > is not so large any more. I'm going to implement rollback as well... Without compensation records... > > * It's more scalable and has less logging contention. This allows > > greater scalablility in the presence of multiple processors. > > Same as above, if you want a txlog you lose. > But if we could switch the txlog off then at least in that mode > we would keep all benefits of the non-overwrite smgr. WAL allows "batch commit" (log commit record, then sleep for ~1/200 sec, now write/fsync log... if no one else didn't fsync-ed it already...) > > * Time travel is available at no cost. > > Yes. Yes, it also solves MVCC. Not with 1sec time grain... But 6+6 bytes per tuple would be enough. Vadim
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