From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
---|---|
To: | Robert Haas <rhaas(at)postgresql(dot)org> |
Cc: | pgsql-committers(at)lists(dot)postgresql(dot)org |
Subject: | Re: pgsql: amcheck: Fix verify_heapam for tuples where xmin or xmax is 0. |
Date: | 2023-03-25 22:24:34 |
Message-ID: | CAH2-WzmEabzcPTxSY-NXKH6Qt3FkAPYHGQSe2PtvGgj17ZQkCw@mail.gmail.com |
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On Fri, Mar 24, 2023 at 8:13 AM Robert Haas <rhaas(at)postgresql(dot)org> wrote:
> If we're checking xmin and find that it is invalid (i.e. 0) just
> report that as corruption, similar to what's already done in the
> three cases that seem correct. If we're checking xmax and find
> that's invalid, that's fine: it just means that the tuple hasn't
> been updated or deleted.
What about aborted speculative insertions? See
heap_abort_speculative(), which directly sets the speculatively
inserted heap tuple's xmin to InvalidTransactionId/zero.
It probably does make sense to keep something close to this check --
it just needs to account for speculative insertions to avoid false
positive reports of corruption. We could perform cross-checks against
a tuple whose xmin is InvalidTransactionId/zero to verify that it
really is from an aborted speculative insertion, to the extent that
that's possible. For example, such a tuple can't be a heap-only tuple,
and it can't have any xmax value other than InvalidTransactionId/zero.
--
Peter Geoghegan
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