Re: multixacts woes

On Mon, May 11, 2015 at 08:29:05AM -0400, Robert Haas wrote:
> Given your concerns, and the need to get a fix for this out the door
> quickly, what I'm inclined to do for the present is go bump the
> threshold from 25% of MaxMultiXact to 50% of MaxMultiXact without
> changing anything else.

+1

> Your analysis shows that this is more in line
> with the existing policy for multixact IDs than what I did, and it
> will reduce the threat of frequent wraparound scans.  Now, it will
> also increase the chances of somebody hitting the wall before
> autovacuum can bail them out.  But maybe not that much.  If we need
> 75% of the multixact member space to complete one cycle of
> anti-wraparound vacuums, we're actually very close to the point where
> the system just cannot work.  If that's one big table, we're done.

Agreed.