A little confused about partial rollbacks in ARIES. When would you need this?
Conversation
Replying to
Subtransactions and statement-level rollback...also important for read committed concurrent update conflicts in some systems.
1
Replying to
@geoghegan86 But if you have a serializable system, you should never need this, correct?
1
Replying to
I think so...Postgres has no undo. Certainly, RC statement rollback thing is basically RC's alternative to serialization failure.
2
Replying to
@geoghegan86 Or is this waht you mean by “RC statement rollback thing”, what is that?
1
Replying to
I mean the way (say) Oracle rolls back entire statement in event of concurrent UPDATE, and retries. Not Postgres, though.
1
Replying to
@geoghegan86 Do you mean rollback entire transaction or individual statements in the transaction? So what does Postgres do?
1
Replying to
Oracle just rolls back statement. Postgres walks update chain, and checks WHERE clause against new tuple: postgresql.org/docs/devel/sta
Replying to
@geoghegan86 Hmm. Are you on the Postgres IRC channel at all? I would be interested to ask a question.
1