Re: [PATCHES] WAL logging freezing

[Alvaro Herrera <alvherre(at)commandprompt(dot)com>]

Gregory Stark wrote:
> 
> "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> 
> > The added WAL volume should be pretty minimal, because only tuples that have
> > gone untouched for a long time incur extra work.
> 
> That seems like a weak point in the logic. It seems like it would make VACUUM
> which is already an i/o hog even more so. Perhaps something clever can be done
> with vacuum_cost_delay and commit_siblings.
> 
> Something like inserting the delay between WAL logging and syncing the log and
> writing to the heap. So if another transaction commits in the meantime we can
> skip the extra fsync and continue.

Huh, but the log would not be flushed for each operation that the vacuum
logs.  Only when it's going to commit.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support