From: | Corey Huinker <corey(dot)huinker(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | 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>, Daniel Verite <daniel(at)manitou-mail(dot)org>, 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: | 2017-02-22 22:11:50 |
Message-ID: | CADkLM=c0h5V+H9aLOjEmc=6naRS2+W6ajZtENy+b3JpkOHZJ+w@mail.gmail.com |
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Lists: | pgsql-hackers |
>
>
> Dunno, that sounds a lot like an "if the only tool I have is a hammer,
> then this must be a nail" argument.
More of a "don't rock the boat more than absolutely necessary", but knowing
that adding another global struct might be welcomed is good to know.
> reasonable interpretation of what it's for. Inventing a PsqlFileState or
> similar struct might be a good idea to help pull some of that cruft out of
> pset and get it back to having a reasonably clearly defined purpose of
> holding "current settings".
>
+1
command was ignored" warning messages). I'm failing to follow why
>
GetVariable would need to care.
>
It took me a second to find the post, written by Daniel Verite on Jan 26,
quoting:
> Revised patch
A comment about control flow and variables:
in branches that are not taken, variables are expanded
nonetheless, in a way that can be surprising.
Case in point:
\set var 'ab''cd'
-- select :var;
\if false
select :var ;
\else
select 1;
\endif
The 2nd reference to :var has a quoting hazard, but since it's within
an "\if false" branch, at a glance it seems like this script might work.
In fact it barfs with:
psql:script.sql:0: found EOF before closing \endif(s)
AFAICS what happens is that :var gets injected and starts a
runaway string, so that as far as the parser is concerned
the \else ..\endif block slips into the untaken branch, as a part of
that unfinished string.
So that was the reasoning behind requiring GetVariable to know whether or
not the statement was being ignored.
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