Re: HOT patch - version 15

"Tom Lane" <tgl@sss.pgh.pa.us> writes:

> 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.

Well we would never be overwriting the blockid, only the posid which is 2
bytes. And the ctid (and posid) should always be 4-byte aligned. So actually
it would never cross a hardware sector boundary.

--
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com