On Fri, Aug 7, 2009 at 12:48 PM, Sam Mason<s...@samason.me.uk> wrote: >> Well most users want compression for the space savings. So running out >> of space sooner than without compression when most of the space is >> actually unused would disappoint them. > > Note, that as far as I can tell for a filesystems you only need to keep > enough reserved for the amount of uncompressed dirty buffers you have in > memory. As space runs out in the filesystem all that happens is that > the amount of (uncompressed?) dirty buffers you can safely have around > decreases.
And when it drops to zero? > In PG's case, it would seem possible to do the compression and then > check to see if the resulting size is greater than 4kB. If it is you > write into the 4kB page size and write uncompressed data. Upon reading > you do the inverse, if it's 4kB then no need to decompress. I believe > TOAST does this already. It does, as does gzip and afaik every compression system. -- greg http://mit.edu/~gsstark/resume.pdf -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers