From: | David Fetter <david(at)fetter(dot)org> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Nico Williams <nico(at)cryptonector(dot)com>, Adam Brusselback <adambrusselback(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: generated columns |
Date: | 2017-10-02 18:36:41 |
Message-ID: | 20171002183641.GE1246@fetter.org |
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Lists: | pgsql-hackers |
On Mon, Oct 02, 2017 at 02:30:38PM -0400, Tom Lane wrote:
> Nico Williams <nico(at)cryptonector(dot)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/
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