Re: Speeding up pg_upgrade

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Cc: Stephen Frost <sfrost(at)snowman(dot)net>, Alexander Kukushkin <cyberdemn(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Speeding up pg_upgrade
Date: 2017-12-07 16:42:08
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Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> It seems pretty clear to me that we should somehow transfer stats from
> the old server to the new one. Shouldn't it just be a matter of
> serializing the MCV/histogram/ndistinct values, then have capabilities
> to load on the new server?

The reason pg_upgrade hasn't done that in the past is not wishing to
assume that the new version does stats identically to the old version.
Since we do in fact add stats or change stuff around from time to time,
that's not a negligible consideration.

regards, tom lane

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