Re: XLByte* usage

Pavan Deolasee <pavan.deolasee@gmail.com>

From: Pavan Deolasee <pavan.deolasee@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Heikki Linnakangas <hlinnakangas@vmware.com>, Andres Freund <andres@2ndquadrant.com>, pgsql-hackers@postgresql.org
Date: 2012-12-17T18:15:51Z
Lists: pgsql-hackers
On Mon, Dec 17, 2012 at 11:26 PM, Pavan Deolasee
<pavan.deolasee@gmail.com> wrote:

>>
>
> I probably did not mean increasing that to beyond 64-bit. OTOH I
> wondered if we would ever want to steal a few bits from the LSN field,
> given the numbers you just put out. But it was more of a question than
> objection.
>

BTW, now that XLogRecPtr is uint64, can't we change the pd_lsn field
to use the same type ? At least the following comment in bufpage.h
looks outdated or at the minimum needs some explanation as why LSN in
the page header needs to split into two 32-bit values.

123 /* for historical reasons, the LSN is stored as two 32-bit values. */
124 typedef struct
125 {
126     uint32      xlogid;         /* high bits */
127     uint32      xrecoff;        /* low bits */
128 } PageXLogRecPtr;


Thanks,
Pavan

-- 
Pavan Deolasee
http://www.linkedin.com/in/pavandeolasee