Horton

Re: Doc patch on psql output formats

Daniel Verite <daniel@manitou-mail.org>

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From: "Daniel Verite" <daniel@manitou-mail.org>
To: "Tom Lane" <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2018-11-06T17:18:37Z
Lists: pgsql-hackers 
	Tom Lane wrote:

> > When a non-unique abbreviation is used, psql uses the first
> > match in an arbitrary order defined in do_pset() by
> > a cascade of pg_strncasecmp().
> 
> Ugh.  Should we not fix the code so that it complains if there's
> not a unique match?  I would bet that the code was also written
> on the assumption that any abbrevation must be unique.

There's a backward compatibility issue, since a script issuing
  \pset format a
would now fail instead of setting the format to "aligned".
The doc patch is meant to describe the current behavior.

OTOH if we don't fail with non-unique matches, there is the risk that
in the future, a new format matching /^a/ will come alphabetically
before "aligned", and will be picked up instead of "aligned".

In both cases using abbreviations in scripts is not a great
idea. Anyway I will look into the changes required in do_pset to
implement the error on multiple matches, if that's the preferred
behavior.

Best regards,
-- 
Daniel Vérité
PostgreSQL-powered mailer: http://www.manitou-mail.org
Twitter: @DanielVerite

Commits

  1. Fix breakage of "\pset format latex".

  2. Make psql's "\pset format" command reject non-unique abbreviations.

  3. Doc: remove claim that all \pset format options are unique in 1 letter.

  4. Reorganize format options of psql in alphabetical order