Re: Separate psql commands from arguments (was: psql command aliases support)

From: Bernd Helmle <mailings(at)oopsware(dot)de>
To: Brendan Jurd <direvus(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Cc: Gregory Stark <stark(at)enterprisedb(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>
Subject: Re: Separate psql commands from arguments (was: psql command aliases support)
Date: 2008-04-03 19:35:22
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--On Freitag, April 04, 2008 05:04:04 +1100 Brendan Jurd
<direvus(at)gmail(dot)com> wrote:

For everyone else who hasn't read the original discussion on -patches,
here's a link into the archives:


> On Fri, Apr 4, 2008 at 4:19 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Yeah, the fundamental difference between the backslash command situation
>> and aliases in shells and suchlike is that, because we've historically
>> allowed no space between command name and argument, it's not that easy
>> to tell what string ought to be compared against alias names.
>> I think that an alias facility would only be acceptably safe if we
>> disallowed that syntax (ie, start to *require* a space between command
>> and args). Are we ready to do that?

Okay, the more we talked about that, the more i got that feeling, too.

> As far as i know, this behaviour isn't documented anywhere. In fact,
> the manual denies its existence:
> "The format of a psql command is the backslash, followed
> immediately by a command verb, then any arguments. The arguments are
> separated from the command verb and each other by any number of
> whitespace characters."

Not only there, the code itself doesn't encourage the use of this syntax
(src/bin/psql/command.c), too:

* If the command was not recognized, try to parse it as a
* command with immediately following argument (a
still-supported, but
* no longer encouraged, syntax).

> (unless you interpret "any number" to include zero, but that's quite a
> stretch in this context)
> For what it's worth, I've been using Postgres actively for about five
> years, and I've not once suspected that it was possible to omit the
> space between a psql command and its argument.
> The idea of writing the command and its arguments in one word is so
> completely bizarre to me that I can't imagine anyone even trying it
> casually to see if it works. Although it is likely that some people
> have stumbled upon it accidentally via typos, it's hard to imagine
> them wanting to use it in any kind of pratical application.
> +1 for dropping this quirk. And, if there are no objections (or other
> takers), I volunteer to write a patch.

Here's a quick and dirty patch which removes the responsible code from psql
(maybe not enough, but short testing shows it's working). Sorry for the
unified diff....

+1, too. I advised people not to use that syntax for years now, maybe we're
in luck and everyone else was doing the same ;)



Attachment Content-Type Size
rm_onetoken_params.patch text/x-diff 972 bytes

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