On Wed, Feb 18, 2015 at 10:57 PM, Kevin Grittner <kgri...@ymail.com> wrote:
> Magnus Hagander <mag...@hagander.net> wrote: > > On Feb 17, 2015 12:26 AM, "Andres Freund" <and...@2ndquadrant.com> > wrote: > >> On 2015-02-16 16:35:46 -0500, Bruce Momjian wrote: > >> But max_standby_streaming_delay, max_standby_archive_delay and > >> hot_standby_feedback are among the most frequent triggers for > >> questions and complaints that I/we see. > >> > > Agreed. > > And a really bad one used to be vacuum_defer_cleanup_age, because > > of confusing units amongst other things. Which in terms seems > > fairly close to Kevins suggestions, unfortunately. > > Particularly my initial suggestion, which was to base snapshot > "age" it on the number of transaction IDs assigned. Does this look > any better to you if it is something that can be set to '20min' or > '1h'? Just to restate, that would not automatically cancel the > snapshots past that age; it would allow vacuum of any tuples which > became "dead" that long ago, and would cause a "snapshot too old" > message for any read of a page modified more than that long ago > using a snapshot which was older than that. > Yes, it would definitely look much better. My reference per above was exactly that - having a setting in the unit "number of xids" confused a lot of users and made it really hard to tune. Having something in time units is a lot easier to understand and tune for most people. -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/
