From: | Noah Misch <noah(at)leadboat(dot)com> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: multixacts woes |
Date: | 2015-05-11 14:11:35 |
Message-ID: | 20150511141135.GB3632096@tornado.leadboat.com |
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Lists: | pgsql-hackers |
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.
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