Date: Mon, 2 Oct 2017 20:36:41 +0200
From: David Fetter <david@fetter.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Nico Williams <nico@cryptonector.com>,
	Adam Brusselback <adambrusselback@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: generated columns
Message-ID: <20171002183641.GE1246@fetter.org>
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On Mon, Oct 02, 2017 at 02:30:38PM -0400, Tom Lane wrote:
> Nico Williams <nico@cryptonector.com> writes:
> > On Mon, Oct 02, 2017 at 12:50:14PM -0400, Adam Brusselback wrote:
> >> So for me, i'd rather default to compute on read, as long storing the
> >> pre-computed value is an option when necessary.
> 
> > Sure, I agree.  I was just wondering whether there might be any other
> > difference besides performance characteristics.  The answer to that is,
> > I think, "no".
> 
> What about non-immutable functions in the generation expression?

Assuming they're permitted, which...well, I could make a case, they
should be mutually exclusive with the cached option.

I guess documenting the behavior in the manual would suffice, tempting
as it would be to include a NOTICE when the table goes from having 0
or more generated columns all of which are immutable to having at
least one that's not.

Best,
David.
-- 
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
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