A little confused about partial rollbacks in ARIES. When would you need this?
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Subtransactions and statement-level rollback...also important for read committed concurrent update conflicts in some systems.
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@geoghegan86 But if you have a serializable system, you should never need this, correct?
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I think so...Postgres has no undo. Certainly, RC statement rollback thing is basically RC's alternative to serialization failure.
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@geoghegan86 No undo? So how does a transaction that fails get aborted?
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@geoghegan86 No undo, just redo. It's related with how WAL is used. It can only move forward, not back.
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@geoghegan86 Or is this waht you mean by “RC statement rollback thing”, what is that?
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I mean the way (say) Oracle rolls back entire statement in event of concurrent UPDATE, and retries. Not Postgres, though.
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