| From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Craig Ringer <craig(dot)ringer(at)2ndquadrant(dot)com>, Ilya Shkuratov <motr(dot)ilya(at)ya(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: CTE inlining |
| Date: | 2017-04-30 05:19:21 |
| Message-ID: | CAFj8pRDS4PoM2inJ9V981OxgD+0h3kg5vrAm5EW7V7SoKt_g_g@mail.gmail.com |
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| Lists: | pgsql-hackers |
2017-04-30 6:28 GMT+02:00 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Craig Ringer <craig(dot)ringer(at)2ndquadrant(dot)com> writes:
> > - as you noted, it is hard to decide when it's worth inlining vs
> > materializing for CTE terms referenced more than once.
>
> [ raised eyebrow... ] Please explain why the answer isn't trivially
> "never".
>
> There's already a pretty large hill to climb here in the way of
> breaking peoples' expectations about CTEs being optimization
> fences. Breaking the documented semantics about CTEs being
> single-evaluation seems to me to be an absolute non-starter.
>
>
why we cannot to introduce GUC option - enable_cteoptfence ?
Regards
Pavel
> regards, tom lane
>
>
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