Date: Tue, 12 Sep 2017 17:52:02 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Andreas Joseph Krogh <andreas@visena.com>
Cc: Michael Paquier <michael.paquier@gmail.com>,
	Robert Haas <robertmhaas@gmail.com>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: Clarification in pg10's pgupgrade.html step 10
 (upgrading standby servers)
Message-ID: <20170912215202.GA6766@momjian.us>
References: <20170912171922.GA3705@momjian.us>
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On Tue, Sep 12, 2017 at 08:59:05PM +0200, Andreas Joseph Krogh wrote:
>     Improvements?
> 
> Thanks, that certainly improves things.
> But; I still find the rsync-command in f) confusing;
> 1. Why --size-only? From rsync manual: "skip files that match in size", is this
> safe??


> 2. Why is old_pgdata in the rsync-command, why is it needed to sync it?

If the file exists under the same name, it doesn't need to be checked at
all --- it is the same.  We don't want to check the file modification
time because it will probably be different because of replay delay or
clock drift.  We could use checksums, but there is no need since there is
no way the file contents could be different.

> There are many ways to do/configure things it seems, resulting in many ifs and
> buts which makes section 10 rather confusing. I really think a complete
> example, with absolute paths, would be clarifying.

You mean a full rsync command, e.g.:

  rsync --archive --delete --hard-links --size-only \
      /opt/PostgreSQL/9.5 /opt/PostgreSQL/9.6 standby:/opt/PostgreSQL

Does that help?

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +


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