From: | Mark Dilger <hornschnorter(at)gmail(dot)com> |
---|---|
To: | David Fetter <david(at)fetter(dot)org> |
Cc: | PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>, Christophe Pettus <xof(at)thebuild(dot)com> |
Subject: | Re: Make autovacuum sort tables in descending order of xid_age |
Date: | 2019-12-12 21:47:23 |
Message-ID: | 49dac8e3-40bc-2986-e873-51f874c0f5fa@gmail.com |
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Lists: | pgsql-hackers |
On 12/12/19 1:35 PM, Mark Dilger wrote:
> Let C = 1.00000002065
> Let x = xid_age for a table
> Let v = clamp(n_dead_tuples / reltuples*2) to max 0.5
> Let a = clamp(changes_since_analyze / reltuples) to max 0.5
>
> Let score = C**x + v + a
I should hasten to add that this is just a proof of concept
formula, not one that I'm specifically advocating. The point
is that we can devise a scoring system in which the xid age
is the dominant factor whenever it could possibly matter,
while still letting other factors prevail when xid age is
of little consequence.
--
Mark Dilger
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