Re: Exposing the Xact commit order to the user - Mailing list pgsql-hackers

From Nicolas Barbier
Subject Re: Exposing the Xact commit order to the user
Date
Msg-id AANLkTik1w8IH91TXq7DcuVL2WDjW51x_1TUshggmUX93@mail.gmail.com
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In response to Re: Exposing the Xact commit order to the user  (Florian Pflug <fgp@phlo.org>)
List pgsql-hackers
2010/5/25 Florian Pflug <fgp@phlo.org>:

> On May 25, 2010, at 20:18 , Dan Ports wrote:
>
>> T3, which is a read-only transaction, sees the incremented date and an
>> empty list of receipts. But T1 later commits a new entry in the
>> receipts table with the old date. No serializable ordering allows this.
>>
>> However, if T3 hadn't performed its read, there'd be no problem; we'd
>> just serialize T1 before T2 and no one would be the wiser.
>
> Hm, so in fact SSI sometimes allows the database to be inconsistent, but only as long as nobody tries to observe it?

I would not call this an inconsistent state: it would become
inconsistent only after someone (e.g., T3) has observed it _and_ T1
commits.

Nicolas


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