On Mon, Dec 14, 2015 at 6:08 PM, Tomas Vondra
<tomas.vondra@2ndquadrant.com> wrote:
> So we know that we should expect about
>
> (prev_wal_bytes - wal_bytes) + (prev_wal_fpw_bytes - wal_fpw_bytes)
>
> ( regular WAL ) + ( FPW WAL )
>
> to be produced until the end of the current checkpoint. I don't have a clear
> idea how to transform this into the 'progress' yet, but I'm pretty sure
> tracking the two types of WAL is a key to a better solution. The x^1.5 is
> probably a step in the right direction, but I don't feel particularly
> confident about the 1.5 (which is rather arbitrary).
If it works well empirically, does it really matter that it's
arbitrary? I mean, the entire planner is full of fairly arbitrary
assumptions about which things to consider in the cost model and which
to ignore. The proof that we have made good decisions there is in the
query plans it generates. (The proof that we have made bad decisions
in some cases in the query plans, too.)
I think a bigger problem for this patch is that Heikki seems to have
almost completely disappeared.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company