On Tue, May 4, 2010 at 5:17 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > FWIW, that's not the case, anymore than it is for blocks in shared > buffer cache for regular rels. smgrextend() results in an observable > extension of the file EOF immediately, whether or not you can see > up-to-date data for those pages. > > Now people have often complained about the extra I/O involved in that, > and it'd be nice to have a solution, but it's not clear to me that > fixing it would be harder for temprels than regular rels.
For systems that have it and filesystems that optimize it I think posix_fallocate() handles this case. We can extend files without actually doing any i/o but we get the guarantee from the filesystem that it has the space available and writing to those blocks won't fail due to lack of space. Only meta-data i/o is triggered allocating the blocks and marking them as virtually filled with nulls and it's not synced unless there's an fsync so there's no extra physical i/o. This should be the case for ext4 but I'm not sure what other filesystems implement this. -- greg -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
