| From: | "Daniel Verite" <daniel(at)manitou-mail(dot)org> |
|---|---|
| To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | "Corey Huinker" <corey(dot)huinker(at)gmail(dot)com>,"David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>,"Fabien COELHO" <coelho(at)cri(dot)ensmp(dot)fr>,"Greg Stark" <stark(at)mit(dot)edu>,"Erik Rijkers" <er(at)xs4all(dot)nl>,"Robert Haas" <robertmhaas(at)gmail(dot)com>,"Jim Nasby" <Jim(dot)Nasby(at)bluetreble(dot)com>,"PostgreSQL" <pgsql-hackers(at)postgresql(dot)org>,pgsql-hackers-owner(at)postgresql(dot)org |
| Subject: | Re: \if, \elseif, \else, \endif (was Re: PSQL commands: \quit_if, \quit_unless) |
| Date: | 2017-03-17 11:33:54 |
| Message-ID: | 9cdc09f7-8e5c-43c9-9c00-2e3bbb69b9ef@manitou-mail.org |
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| Lists: | pgsql-hackers |
Tom Lane wrote:
> OT_WHOLE_LINE is not what you want because that results in verbatim
> copying, without variable expansion or anything
But if we want to implement "\if defined :foo" in the future
isn't it just what we need?
Also we could leave open the option to accept an SQL expression
here. I expect people will need SQL as the evaluator in a lot of cases.
So far we need to do that:
SELECT sql_expr ... AS varname \gset
\if :varname
...
\endif
Surely users will wonder right away why they can't write it like this
instead:
\if (sql_expr)
...
\endif
There's a precedent with \copy accepting a query inside parentheses,
using OT_WHOLE_LINE.
Best regards,
--
Daniel Vérité
PostgreSQL-powered mailer: http://www.manitou-mail.org
Twitter: @DanielVerite
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