On Mon, Mar 15, 2010 at 10:53 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Greg Smith <greg@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.
