From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>, michael@paquier.xyz,
        kuntalghosh.2007@gmail.com, pgsql-hackers@lists.postgresql.org
Subject: Re: Regression test PANICs with master-standby setup on same machine
In-reply-to: <20190424162449.3jrna4iqjm3nzmz2@alap3.anarazel.de>
References: <20190423170503.uw5jxrujqlozg23l@alap3.anarazel.de>
 <20190424.131845.116224815.horiguchi.kyotaro@lab.ntt.co.jp>
 <20190424.132304.40676137.horiguchi.kyotaro@lab.ntt.co.jp>
 <20190424.170228.203880527.horiguchi.kyotaro@lab.ntt.co.jp>
 <10967.1556115189@sss.pgh.pa.us>
 <20190424162449.3jrna4iqjm3nzmz2@alap3.anarazel.de>
Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Wed, 24 Apr 2019 09:24:49 -0700"
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Date: Wed, 24 Apr 2019 13:02:03 -0400
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Andres Freund <andres@anarazel.de> writes:
> On 2019-04-24 10:13:09 -0400, Tom Lane wrote:
>> I can't say that I like 0001 at all.  It adds a bunch of complication and
>> new failure modes (e.g., having to panic on chdir failure) in order to do
>> what exactly?  I've not been following the thread closely, but the
>> original problem is surely just a dont-do-that misconfiguration.  I also
>> suspect that this is assuming way too much about the semantics of getcwd
>> --- some filesystem configurations may have funny situations like multiple
>> paths to the same place.

> I'm not at all defending the conrete patch. But I think allowing
> relative paths to tablespaces would solve a whole lot of practical
> problems, while not meaningfully increasing failure modes.

I'm not against allowing relative tablespace paths.  But I did not like
the chdir and getcwd-semantics hazards --- why do we have to buy into
all that to allow relative paths?

I think it would likely be sufficient to state plainly in the docs
that a relative path had better point outside $PGDATA, and maybe
have some *simple* tests on the canonicalized form of the path to
prevent obvious mistakes.  Going further than that is likely to add
more problems than it removes.

			regards, tom lane