On Thu, Dec 11, 2008 at 5:01 PM, Zdenek Kotala <[EMAIL PROTECTED]> wrote: > >> > > IIRC, Memory reading/writing is atomic operation. Only one CPU(hw thread) > can access to the same memory address(es)* in same time*. The question is > how compiler compile C code to assembler. But this code seems to me safe.
Yeah, I think the code is safe because we are just reading a bit. BTW, I wonder if we need to acquire EXCLUSIVE lock while writing the visibility map bit ? Since almost (8 * 8192) data blocks would map to the same visibility map page, the lock can certainly become a hot spot. I know we also update PageLSN during the set operation and that would require EXLUSIVE lock, but is that required for consistency given that the entire visibility map is just a hint ? Thanks, Pavan -- Pavan Deolasee EnterpriseDB http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
