Re: preserving forensic information when we freeze

On Fri, Dec 20, 2013 at 1:41 PM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> 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.

I don't understand what you're saying here.  Are you saying that
reloid/ctid is a better approach, a worse approach, or just a
different approach?

--
Robert Haas
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