Re: [PATCH] pageinspect function to decode infomasks

On Sat, Oct 14, 2017 at 10:58 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> I think it's perfectly sensible to view those 2 bits as making up a
> 2-bit field with 4 states rather than displaying each bit
> individually, but you obviously disagree.  Fair enough.

I guess it is that simple.

> I can think of two possible explanations for that.  Number one, the
> tool was written before HEAP_XMIN_FROZEN was invented and hasn't been
> updated for those changes.

Have we invented our last t_infomask/t_infomask2 (logical) status already?

> Number two, the author of the tool agrees
> with your position rather than mine.

I am working on an experimental version of pg_filedump, customized to
output XML that can be interpreted by an open source hex editor. The
XML makes the hex editor produce color coded, commented
tags/annotations for any given heap or B-Tree relation. This includes
tooltips with literal values for all status bits (including
t_infomask/t_infomask2 bits, IndexTuple bits, B-Tree meta page status
bits, PD_* page-level bits, ItemId bits, and others). I tweeted about
this several months ago, when it was just a tool I wrote for myself,
and received a surprisingly positive response. It seems like I'm on to
something, and should release the tool to the community.

I mention this project because it very much informs my perspective
here. Having spent quite a while deliberately corrupting test data in
novel ways, just to see what happens, the "work backwards from the
storage format" perspective feels very natural to me. I do think that
I understand where you're coming from too, though.

-- 
Peter Geoghegan