Re: multixacts woes

Josh Berkus wrote:

> In terms of adding a new GUC in 9.5: can't we take a stab at auto-tuning
> this instead of adding a new GUC?  We already have a bunch of freezing
> GUCs which fewer than 1% of our user base has any idea how to set.

If you have development resources to pour onto 9.5, I think it would be
better spent changing multixact usage tracking so that oldestOffset is
included in pg_control; also make pg_multixact truncation be WAL-logged.
With those changes, the need for a lot of pretty complicated code would
go away.  The fact that truncation is done by both vacuum and checkpoint
causes a lot of the mess we were in (and from which Robert and Thomas
took us --- thanks guys!).  Such a change is the first step towards
auto-tuning, I think.

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
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