On 19 March 2013 17:18, Jeff Davis <pg...@j-davis.com> wrote: > I will move back to verifying the page hole, as well.
That was agreed long ago... > There are a few approaches: > > 1. Verify that the page hole is zero before write and after read. > 2. Include it in the calculation (if we think there are some corner > cases where the hole might not be all zero). > 3. Zero the page hole before write, and verify that it's zero on read. > This can be done during the memcpy at no performance penalty in > PageSetChecksumOnCopy(), but that won't work for > PageSetChecksumInplace(). > > With option #2 or #3, we might also verify that the hole is all-zero if > asserts are enabled. (3) seems likely to be more expensive than (2), since we're talking unaligned memory writes rather than a single pre-fetchable block read. In any case, at initial patch commit, we should CRC the whole block and allow for the possibility of improvement following measurements. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
