From: | Jan Wieck <JanWieck(at)Yahoo(dot)com> |
---|---|
To: | Greg Sabino Mullane <greg(at)turnstep(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Exposing the Xact commit order to the user |
Date: | 2010-05-24 01:18:39 |
Message-ID: | 4BF9D3EF.7000902@Yahoo.com |
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Thread: | |
Lists: | pgsql-hackers |
On 5/23/2010 4:48 PM, Greg Sabino Mullane wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: RIPEMD160
>
>
>> Exposing the data will be done via a set returning function. The SRF
>> takes two arguments. The maximum number of rows to return and the last
>> serial number processed by the reader. The advantage of such SRF is that
>> the result can be used in a query that right away delivers audit or
>> replication log information in transaction commit order. The SRF can
>> return an empty set if no further transactions have committed since, or
>> an error if data segments needed to answer the request have already been
>> purged.
>
> In light of the proposed purging scheme, how would it be able to distinguish
> between those two cases (nothing there yet vs. was there but purged)?
There is a difference between an empty result set and an exception.
Jan
--
Anyone who trades liberty for security deserves neither
liberty nor security. -- Benjamin Franklin
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