On Thu, Feb 23, 2017 at 03:45:24PM -0300, Alvaro Herrera wrote: > Bruce Momjian wrote: > > > Well, let's walk through this. Let's suppose you have three updates > > that stay on the same page and don't update any indexed columns --- that > > would produce a HOT chain of four tuples. If you then do an update that > > changes an indexed column, prior to this patch, you get a normal update, > > and more HOT updates can be added to this. With WARM, we can join those > > chains > > With WARM, what happens is that the first three updates are HOT updates > just like currently, and the fourth one is a WARM update.
Right. > > and potentially trim the first HOT chain as those tuples become > > invisible. > > That can already happen even without WARM, no? Uh, the point is that with WARM those four early tuples can be removed via a prune, rather than requiring a VACUUM. Without WARM, the fourth tuple can't be removed until the index is cleared by VACUUM. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + As you are, so once was I. As I am, so you will be. + + Ancient Roman grave inscription + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
