Re: increasing the default WAL segment size

Hello,

On Tue, Jan 3, 2017 at 5:46 PM, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
wrote:

> On Tue, Jan 3, 2017 at 6:23 AM, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>
> wrote:
> > + /* Check if wal_segment_size is in the power of 2 */
> > + for (i = 0;; i++, pow2 = pow(2, i))
> > + if (pow2 >= wal_segment_size)
> > + break;
> > +
> > + if (wal_segment_size != 1 && pow2 > wal_segment_size)
> > + {
> > + fprintf(stderr, _("%s: WAL segment size must be
> in the power of 2\n"), progname);
> > + exit(1);
> > + }
>
> I recall taht pow(x, 2) and x * x result usually in the same assembly
> code, but pow() can never be more optimal than a simple
> multiplication. So I'd think that it is wiser to avoid it in this code
> path. Documentation is missing for the new replication command
> SHOW_WAL_SEG.

As mentioned earlier, documents are not fully updated.

> Actually, why not just having an equivalent of the SQL
> command and be able to query parameter values?
>

This patch only needed the wal_segment_size and hence I made this specific
command.
How often and why would we need other parameter values in the replication
connection?
Making it a more general command to fetch any parameter can be a separate
topic. If it gets consensus, maybe it could be done and used here.

Thank you,

Beena Emerson

Have a Great Day!