Re: Re: [COMMITTERS] pgsql: Adjust OLDSERXID_MAX_PAGE based on BLCKSZ.

On 08.07.2011 15:22, Kevin Grittner wrote:
> Heikki Linnakangas wrote:
>
>> I'm getting a bunch of warnings on Windows related to this:
>
>>> .\src\backend\storage\lmgr\predicate.c(768): warning C4307: '+' :
>>> integral constant overflow
>
> The part of the expression which is probably causing this:
>
> (MaxTransactionId + 1) / OLDSERXID_ENTRIESPERPAGE - 1
>
> Which I fear may not be getting into overflow which will not do the
> right thing even where there is no warning. :-(
>
> Would it be safe to assume that integer division would do the right
> thing if we drop both of the "off by one" adjustments and use?:
>
> MaxTransactionId / OLDSERXID_ENTRIESPERPAGE

Hmm, that seems more correct to me anyway. We are trying to calculate
which page xid MaxTransactionId would be stored on, if the SLRU didn't
have a size limit. You calculate that with simply MaxTransactionId /
OLDSERXID_ENTRIESPERPAGE.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com