| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> |
| Cc: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp>, rafia(dot)sabih(at)enterprisedb(dot)com, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] pgbench - allow to store select results into variables |
| Date: | 2018-11-16 22:13:13 |
| Message-ID: | 20181116221313.nwc3ozw3tqvkzsec@alvherre.pgsql |
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| Thread: | |
| Lists: | pgsql-hackers |
On 2018-Nov-16, Alvaro Herrera wrote:
> On 2017-Nov-04, Fabien COELHO wrote:
>
> > Think of one initialization followed by two appends:
> >
> > SELECT 1 AS x \cset
> > SELECT 2 \; SELECT 3 AS y \cset
> > SELECT 4 \; SELECT 5 \; SELECT 6 AS z \gset
> >
> > In the end, we must have the full 6 queries
> >
> > "SELECT 1 AS x \; SELECT 2 \; SELECT 3 AS y \; SELECT 4 \; SELECT 5 \; SELECT 6 AS z"
> >
> > and know that we want to set variables from queries 1, 3 and 6 and ignore
> > the 3 others.
>
> I'm not sure I understand this. Why is the "SELECT 2" ignored? (I can
> see why the 4 and 5 are ignored: they are not processed by gset).
>
> What exactly does \cset do?
Oh! I understand it now. You say "replace a semicolon" to mean "works
as if it were a semicolon, and also captures the result". So \cset
means "works as if it were an escaped semicolon". It all suddenly makes
sense now! I think I'll propose some rewording of that explanation, as
it was very confusing to me.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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