Re: Freeze avoidance of very large table.

On Sat, Nov 14, 2015 at 1:19 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2015-10-31 11:02:12 +0530, Amit Kapila wrote:
> > On Thu, Oct 8, 2015 at 11:05 PM, Simon Riggs <simon(at)2ndquadrant(dot)com>
wrote:
> > >
> > > On 1 October 2015 at 23:30, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> > >>
> > >> On 10/01/2015 07:43 AM, Robert Haas wrote:
> > >> > On Thu, Oct 1, 2015 at 9:44 AM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
> > wrote:
> > >> >> I wonder how much it's worth renaming only the file extension
while
> > >> >> there are many places where "visibility map" and "vm" are used,
> > >> >> for example, log messages, function names, variables, etc.
> > >> >
> > >> > I'd be inclined to keep calling it the visibility map (vm) even if
it
> > >> > also contains freeze information.
> > >> >
> >
> > What is your main worry about changing the name of this map, is it
> > about more code churn or is it about that we might introduce new issues
> > or is it about that people are already accustomed to call this map as
> > visibility map?
>
> Several:
> * Visibility map is rather descriptive, none of the replacement terms
> imo come close. Few people will know what a 'freeze' map is.
> * It increases the size of the patch considerably
> * It forces tooling that knows about the layout of the database
> directory to change their tools
>

All these points are legitimate.

> On the benfit side the only argument I've heard so far is that it allows
> to disambiguate the format. But, uh, a look at the major version does
> that just as well, for far less trouble.
>
> > It seems to me quite logical for understanding purpose as well. Any new
> > person who wants to work in this area or is looking into it will always
> > wonder why this map is named as visibility map even though it contains
> > information about visibility of page as well as frozen state of page.
>
> Being frozen is about visibility as well.
>

OTOH being visible doesn't mean page is frozen. I understand that frozen is
related to visibility, but still it is a separate state of page and used
for different
purpose. I think this is a subjective point and we could go either way, it
is
just a matter in which way more people are comfortable.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com