On 3/8/19 4:19 PM, Julien Rouhaud wrote: > On Thu, Mar 7, 2019 at 7:00 PM Andres Freund <and...@anarazel.de> wrote: >> >> On 2019-03-07 12:53:30 +0100, Tomas Vondra wrote: >>> >>> But then again, we could just >>> hack a special version of ReadBuffer_common() which would just >> >>> (a) check if a page is in shared buffers, and if it is then consider the >>> checksum correct (because in memory it may be stale, and it was read >>> successfully so it was OK at that moment) >>> >>> (b) if it's not in shared buffers already, try reading it and verify the >>> checksum, and then just evict it right away (not to spoil sb) >> >> This'd also make sense and make the whole process more efficient. OTOH, >> it might actually be worthwhile to check the on-disk page even if >> there's in-memory state. Unless IO is in progress the on-disk page >> always should be valid. > > Definitely. I already saw servers with all-frozen-read-only blocks > popular enough to never get evicted in months, and then a minor > upgrade / restart having catastrophic consequences. >
Do I understand correctly the "catastrophic consequences" here are due to data corruption / broken checksums on those on-disk pages? regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
