| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: lcr v5 - introduction of InvalidCommandId |
| Date: | 2013-09-05 16:59:44 |
| Message-ID: | 20130905165944.GB349020@alap2.anarazel.de |
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| Thread: | |
| Lists: | pgsql-hackers |
On 2013-09-05 12:44:18 -0400, Robert Haas wrote:
> On Wed, Sep 4, 2013 at 12:07 PM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> > On 2013-09-03 11:40:57 -0400, Robert Haas wrote:
> >> > 0002 wal_decoding: Introduce InvalidCommandId and declare that to be the new maximum for CommandCounterIncrement
> >>
> >> I'm still unconvinced we want this.
> >
> > Ok, so the reason for the existance of this patch is that currently
> > there is no way to represent a "unset" CommandId. This is a problem for
> > the following patches because we need to log the cmin, cmax of catalog
> > rows and obviously there can be rows where cmax is unset.
>
> For heap tuples, we solve this problem by using flag bits. Why not
> adopt the same approach?
We can, while it makes the amount of data stored/logged slightly larger
and it seems to lead to less idiomatic code to me, so if there's another
-1 I'll go that way.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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