Re: index-only scans vs. Hot Standby, round two

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Simon Riggs <simon(at)2ndQuadrant(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: index-only scans vs. Hot Standby, round two
Date: 2012-04-16 14:19:36
Message-ID: 24054.1334585976@sss.pgh.pa.us
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Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> Can we have a "soft" hot standby conflict that doesn't kill the query,
> but disables index-only-scans?

Well, there wouldn't be any way for the planner to know whether an
index-only scan would be safe or not. I think this would have to look
like a run-time fallback. Could it be structured as "return that the
page's all-visible bit is not set, instead of failing?" Or am I
confused about where the conflict is coming from?

regards, tom lane

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