Hi, It's simply because we should not refer to system catalog during the recovery.
2009/1/25 Gregory Stark <st...@enterprisedb.com>: > > Koichi Suzuki <koichi....@gmail.com> writes: > >> Please find enclosed 2nd patch of pg_readahead which include a patch >> to bufer manager to skip prefetch of pages already in shared buffer. > > I'm a bit confused by this comment. PrefetchBuffer already checks if the page > is in shared buffers. > > What is tricky to avoid is prefetching the same page twice -- since the first > prefetch doesn't actually put it in shared buffers there's no way to avoid > prefetching it again unless you keep some kind of hash of recently prefetched > buffers. > > For the index scan case I'm debating about whether to add such a cache > directly to PrefetchBuffer -- in which case it would remember if some other > scan prefetched the same buffer -- or to keep it in the index scan code. > > -- > Gregory Stark > EnterpriseDB http://www.enterprisedb.com > Ask me about EnterpriseDB's On-Demand Production Tuning > -- ------ Koichi Suzuki -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
