Re: Freeze avoidance of very large table.

On Tue, Feb 2, 2016 at 10:15 AM, Jim Nasby <Jim.Nasby@bluetreble.com> wrote:
> On 2/1/16 4:59 PM, Alvaro Herrera wrote:
>>
>> Masahiko Sawada wrote:
>>
>>> Attached updated version patch.
>>> Please review it.
>>
>>
>> In pg_upgrade, the "page convert" functionality is there to abstract
>> rewrites of pages being copied; your patch is circumventing it and
>> AFAICS it makes the interface more complicated for no good reason.  I
>> think the real way to do that is to write your rewriteVisibilityMap as a
>> pageConverter routine.  That should reduce some duplication there.
>

This means that user always have to set pageConverter plug-in when upgrading?
I was thinking that this conversion is required for all user who wants
to upgrade to 9.6, so we should support it in core, not as a plug-in.

>
> IIRC this is about the third problem that's been found with pg_upgrade in
> this patch. That concerns me given the potential for disaster if freeze bits
> are set incorrectly.

Yeah, I tend to have diagnostic tool for visibilitymap, and to exactly
compare VM between old one and new one after upgrading postgres
server.
I've implemented a such tool that is in my github repository[1].
I'm thinking to add this tool into core(e.g., pg_upgrade directory,
not contrib module) as testing function.

[1] https://github.com/MasahikoSawada/pg_visibilitymap

Regards,

--
Masahiko Sawada