On Mon, Mar 15, 2010 at 10:53 AM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> Greg Smith <g...@2ndquadrant.com> writes: > > VJK wrote: > >> Since Pg does not use the concept of rollback segments, it is unclear > >> why deletion produces so much disk IO (4GB). > > For an example like this one, you have to keep in mind that the > toast-table rows for the large bytea value have to be marked deleted, > too. Also, since I/O happens in units of pages, the I/O volume to > delete a tuple is just as much as the I/O to create it. > That makes sense. > regards, tom lane >
