Re: preserving forensic information when we freeze

Robert Haas escribió:
> On Fri, Dec 20, 2013 at 7:22 AM, Andres Freund <andres@2ndquadrant.com> wrote:
> >> Maybe what we should do is add a function something like
> >> pg_tuple_header(tableoid, ctid) that returns a record, maybe something
> >> like (rawxmin xid, rawxmax xid, rawcid cid, infomask int, infomask2
> >> int, hoff int).  Or perhaps some slightly more cooked version of that
> >> information.  And then delete the xmin, xmax, cmin, and cmax system
> >> columns.  That'd save significantly on pg_attribute entries while, at
> >> the same time, actually providing more information than we do today.
> >
> > I was wondering whether we couldn't just pass pg_tuple_header() a whole
> > row, instead of having the user manually pass in reloid and ctid. I
> > think that should actually work in the interesting scenarios.
> 
> I wondered that, too, but it's not well-defined for all tuples.  What
> happens if you pass in constructed tuple rather than an on-disk tuple?

I assume without checking that passing reloid/ctid would allow this to
work for tuples in a RETURNING clause; and if we ever have an OLD
reference for the RETURNING clause of an UPDATE, that it would work
there, too, showing the post-update status of the updated tuple.

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
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