Re: initdb -S and tablespaces

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Abhijit Menon-Sen <ams(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: initdb -S and tablespaces
Date: 2015-05-09 21:40:50
Message-ID: 13545.1431207650@sss.pgh.pa.us
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Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2015-05-08 22:08:31 -0400, Robert Haas wrote:
>> Of course, even the last one isn't totally bullet-proof. Suppose one
>> backend fails to absorb the new setting for some reason...

> I've a hard time worrying much about that one...

You should. At the very least, whatever recipe we write for changing
fsync safely has to include a clause like "wait for all postmaster
children to have absorbed the new fsync setting". The facts that (a) this
could be a long time and (b) there's no easy way to be entirely certain
about when it's done don't make it something you should ignore.

I wonder whether we should change fsync to be PGC_POSTMASTER and then
document the safe procedure as requiring a postmaster restart.

regards, tom lane

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