Re: testing HS/SR - 1 vs 2 performance

On Apr 21, 2010, at 16:49 , Simon Riggs wrote:
> On Wed, 2010-04-21 at 16:22 +0200, marcin mank wrote:
>
>> Is that not a good idea that (at least for dev-builds, like with
>> enable-cassert) the xid counter start at like 2^31 - 1000 ? It could
>> help catch some bugs.
>
> It is a good idea, I'm sure that would help catch bugs.
>
> It wouldn't help here because the case in doubt is whether it's possible
> to have an xid still showing in memory arrays from the last time the
> cycle wrapped. It isn't. These things aren't random. These numbers are
> extracted directly from activity that was occurring on the primary and
> regularly checked and cleaned as the standby runs.
>
> So you'll need to do 2^31 transactions to prove this isn't true, which
> isn't ever going to happen in testing with an assert build and nobody
> with that many transactions would run an assert build anyway.


ISTM that there's no need to actually execute 2^31 transactions to trigger this bug (if it actually exists), it'd be
sufficientto increment the xid counter by more than one each time a xid is assigned, no? 

Or would that trip snapshot creation on the standby?

best regards,
Florian Pflug