On Thu, Jun 16, 2011 at 6:54 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 4. Backend #2 visits the new, about-to-be-committed version of
> pgbench_accounts' pg_class row just before backend #3 commits.
> It sees the row as not good and keeps scanning. By the time it
> reaches the previous version of the row, however, backend #3
> *has* committed. So that version isn't good according to SnapshotNow
> either.
<thinks some more>
Why isn't this a danger for every pg_class update? For example, it
would seem that if VACUUM updates relpages/reltuples, it would be
prone to this same hazard.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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