On Wed, Jan 11, 2017 at 2:20 PM, Peter Geoghegan <pg@heroku.com> wrote:
> You'd probably still want to throw an error when workers ended up not
> deleting BufFile segments they owned, though, at least for parallel
> tuplesort.
Don't see why.
> This idea is something that's much more limited than the
> SharedTemporaryFile() API that you sketched on the parallel sort
> thread, because it only concerns resource management, and not how to
> make access to the shared file concurrency safe in any special,
> standard way.
Actually, I only intended that sketch to be about resource management.
Sounds like I didn't explain very well.
> Instead, they should be passing around some kind of minimal
> private-to-buffile state in shared memory that coordinates backends
> participating in BufFile unification. Private state created by
> buffile.c, and passed back to buffile.c. Everything should be
> encapsulated within buffile.c, IMV, making parallel implementations as
> close as possible to their serial implementations.
That seems reasonable although I haven't studied the details carefully as yet.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company