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Date: Wed, 27 Jan 2021 15:06:46 +0100
From: Jehan-Guillaume de Rorthais <jgdr@dalibo.com>
To: Andres Freund <andres@anarazel.de>
Cc: Denis Laxalde <denis.laxalde@dalibo.com>,
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Subject: Re: [PATCH] Disable bgworkers during servers start in pg_upgrade
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Oh, I forgot another point before sending my previous email.

Maybe it might worth adding some final safety checks in pg_upgrade itself?
Eg. checking controldata and mxid files coherency between old and new
cluster would have catch the inconsistency here.