Re: Undefined psql variables

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: Corey Huinker <corey(dot)huinker(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Undefined psql variables
Date: 2017-04-08 10:25:28
Message-ID: alpine.DEB.2.20.1704081204420.22037@lancre
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Hello Pavel,
> you proposal disallow client side expressions.

I do agree that some client side expressions are necessary. I do not want
to disallow them.

> I agree so is not possible to mix server side and client side
> expressions.

My point is that a minimal of cross-support is possible.

> But I am sceptic so benefit of server side expression is higher than a
> lost of client side expressions.

There is a misunderstanding. I am not against client side expression. I do
want to allow the same server & client side capabilities suggested by Tom,
I'm just arguing about the syntax, to avoid a prefix oriented approach.

> If we disallow server side expressions, then your examples are only two
> lines longer, but the implementation can be more simpler.
> SELECT version FROM app_version
> \gset
> \if :version >= 2.0
> ...
> Still I don't think so server side expression in \if is good idea.

Ok, so you do not like server-side expression capabities integrated to
\if. I understood that you were in favor of Tom's proposal.

From a semantical point of view they are not necessary because the same
effect can be obtained through \gset, at the price of an intermediate
variable. So the server-side thing is just a syntax convenience. I think
that independently of whether they are added, Tom's point is that it
should be possible to add those features later on, hence the discussion
about a design.


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