Hi,
On 2020-09-14 17:00:48 -0400, Robert Haas wrote:
> On Mon, Sep 14, 2020 at 4:13 PM Andres Freund <andres@anarazel.de> wrote:
> > My understanding of the case we're discussing is that it's corruption
> > (e.g. relfrozenxid being different than table contents) affecting a HOT
> > chain. I.e. by definition all within a single page. We won't have
> > modified part of it independent of B < A, because freezing is
> > all-or-nothing. Just breaking the HOT chain into two or something like
> > that will just make things worse, because indexes won't find tuples, and
> > because reindexing might then get confused e.g. by HOT chains without a
> > valid start, or by having two visible tuples for the same PK.
>
> If we adopt the proposal made by Dilip, we will not do that. We must
> have a.xmax = b.xmin, and that value is either less than relfrozenxid
> or it is not. If we skip an entire tuple because one XID is bad, then
> we could break the HOT chain when a.xmin is bad and the remaining
> values are OK. But if we decide separately for xmin and xmax then we
> should be alright.
I thought I precisely addressed this case:
> What exactly are you going to put into xmin/xmax here? And how would
> anything you put into the first tuple not break index lookups? There's
> no such thing as a frozen xmax (so far), so what are you going to put
> in there? A random different xid? FrozenTransactionId?
> HEAP_XMAX_INVALID?
What am I missing?
Greetings,
Andres Freund
