Re: Re: [COMMITTERS] pgsql: Adjust OLDSERXID_MAX_PAGE based on BLCKSZ. - Mailing list pgsql-hackers

From Kevin Grittner
Subject Re: Re: [COMMITTERS] pgsql: Adjust OLDSERXID_MAX_PAGE based on BLCKSZ.
Date
Msg-id 4E16C3BA020000250003F0F3@gw.wicourts.gov
Whole thread Raw
In response to Re: Re: [COMMITTERS] pgsql: Adjust OLDSERXID_MAX_PAGE based on BLCKSZ.  (Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>)
Responses Re: Re: [COMMITTERS] pgsql: Adjust OLDSERXID_MAX_PAGE based on BLCKSZ.
List pgsql-hackers
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.

-Kevin


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