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Re: [HACKERS] psql \copy warning

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Jeremy Drake <pgsql(at)jdrake(dot)com>, PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: [HACKERS] psql \copy warning
Date: 2006-05-29 04:05:32
Message-ID: 200605290405.k4T45Wc25456@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Right.  I think the question is whether we want all psql strings to
> > accept backslashes, and hence not support E'' at all for psql commands.
> > I figured that made the most sense.
> 
> I'm not convinced.  Wouldn't it be better if psql commands track the
> backend syntax?  With standard_conforming_strings on, there will be two
> ways to tell COPY you want a tab as a delimiter:
> 	DELIMITER '<actual tab char>'
> 	DELIMITER E'\t'
> and in particular this will NOT do that:
> 	DELIMITER '\t'

Well, I think it a little more confusing that just \copy.  What about \d
and \set uses of backslashes.  Do they honor standard_conforming_strings
too?  I assume you are saying they should.

> If we keep '\t' as meaning tab in the \copy syntax then I think we're
> going to cause confusion in the long run.  I think we should fix \copy
> and related psql backslash commands to accept E'\t', and make sure that
> the behavior is the same as the connected backend depending on what its 
> standard_conforming_strings setting is.

OK, though this is going to mean that examples in the psql manual page
are going to be different for different standard_conforming_strings
settings:

       testdb=> \set content '\'' `cat my_file.txt` '\''
       testdb=> INSERT INTO my_table VALUES (:content);

psql doesn't know '''' is about doubling single quotes in a string,
though \copy does.  The major problem, I think, is that psql often
follows the shell rules, rather than the SQL rules for most things.

> There is a secondary, largely cosmetic question of whether psql should
> attempt to prevent you from seeing escape_string_warning messages.
> I personally have come to the conclusion that escape_string_warning is
> probably not going to be on by default anyway ;-), and hence it's not
> worth going to great extremes to prevent this, particularly if it breaks
> the ability to use psql against pre-8.1 servers.

It does break backward compatibility.

-- 
  Bruce Momjian   http://candle.pha.pa.us
  EnterpriseDB    http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

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