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

On 08.07.2011 16:45, Kevin Grittner wrote:
> Heikki Linnakangas<heikki.linnakangas@enterprisedb.com>  wrote:
>> On 08.07.2011 15:22, Kevin Grittner wrote:
>
>>>     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.
>
> Good point.  The old calculation was finding the page before the
> page which would contain the first out-of-bound entry.  As long as
> these numbers are all powers of 2 that's the same, but (besides the
> overflow issue) it's not as clear.
>
> On the off chance that this saves someone any work, trivial patch
> attached.

There was still one warning left after that:

.\src\backend\storage\lmgr\predicate.c(770): warning C4146: unary minus 
operator applied to unsigned type, result still unsigned

It's coming from this line:

>     else if (diff < -((OLDSERXID_MAX_PAGE + 1) / 2))


I fixed that by adding a cast to int there, and committed.

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