Re: lcr v5 - introduction of InvalidCommandId

On Thu, Sep 5, 2013 at 12:59 PM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> 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.

OK. Consider me more of a -0 than a -1. Like I say, I don't really
want to block it; I just don't feel comfortable committing it unless a
few other people say something like "I don't see a problem with that".
Or maybe point me to relevant changeset extraction code that's going
to get messier.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company