| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | Andreas Karlsson <andreas(at)proxel(dot)se> |
| Cc: | David Fetter <david(at)fetter(dot)org>, Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: CTE inlining |
| Date: | 2017-05-01 14:53:06 |
| Message-ID: | CAKFQuwaxWAOB8kCwwJjAx=co+Nmmy5_HOgs37_-jRoUqc09=Rg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, May 1, 2017 at 7:43 AM, Andreas Karlsson <andreas(at)proxel(dot)se> wrote:
> On 05/01/2017 04:33 PM, David G. Johnston wrote:
> > On Mon, May 1, 2017 at 7:26 AM, Andreas Karlsson <andreas(at)proxel(dot)se
> > I am not sure I like decorators since this means adding an ad hoc
> > query hint directly into the SQL syntax which is something which I
> > requires serious consideration.
>
> > I would shorten that to "WITH MAT" except that I don't think that
> > having two way to introduce an optimization fence is worthwhile.
>
> You mean OFFSET 0? I have never been a fan of using it as an optimization
> fence. I do not think OFFSET 0 conveys clearly enough to the reader that is
> is an optimization fence.
I think I was being too literal in my thinking. Proposing that we
effectively do away with OFFSET 0 and instead recommend "WITH MAT name AS
()" for subqueries requiring standalone evaluation is something I can agree
with. I too have always though of OFFSET 0 as hack-ish which is why my SRF
usage examples have always used CTEs.
David J.
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