Re: HOT patch - version 15

Simon Riggs <simon@2ndquadrant.com> writes:
> On Tue, 2007-09-11 at 01:22 +0530, Pavan Deolasee wrote:
>> I think the only difference is that the quick pruning does not mark
>> intermediate tuples ~LP_USED and hence we may avoid WAL logging.

> Sounds great.

What it sounds is utterly unsafe.  You can get away with not WAL-logging
individual bit flips (that is, hint-bit-setting) because either state of
the page is valid.  If I read this proposal correctly it is to change
t_ctid without WAL-logging, which means that a partial page write (torn
page syndrome) could leave the page undetectably corrupted --- t_ctid
is 6 bytes and could easily cross a hardware sector boundary.

            regards, tom lane