Re: pgsql: Re-allow DISTINCT in pl/pgsql expressions.

On Fri, Jan 22, 2021 at 07:04:20PM -0500, Bruce Momjian wrote:
> On Fri, Jan 22, 2021 at 09:26:29PM +0000, Tom Lane wrote:
> > Re-allow DISTINCT in pl/pgsql expressions.
> > 
> > I'd omitted this from the grammar in commit c9d529848, figuring that
> > it wasn't worth supporting.  However we already have one complaint,
> > so it seems that judgment was wrong.  It doesn't require a huge
> > amount of code, so add it back.  (I'm still drawing the line at
> > UNION/INTERSECT/EXCEPT though: those'd require an unreasonable
> > amount of grammar refactoring, and the single-result-row restriction
> > makes them near useless anyway.)
> > 
> > Also rethink the documentation: this behavior is a property of
> > all pl/pgsql expressions, not just assignments.
> > 
> > Discussion: https://postgr.es/m/20210122134106.e94c5cd7@mail.verfriemelt.org
> 
> I am seeing a warning generated by preproc.y, which is generated via
> Perl from gram.y, which was modified by this commit.  The bison output
> is:
> 
>     $ /usr/bin/bison -Wno-deprecated  -d -o preproc.c preproc.y
>     preproc.y: warning: 1 nonterminal useless in grammar [-Wother]
>     preproc.y: warning: 2 rules useless in grammar [-Wother]
>     preproc.y:10134.2-20: warning: nonterminal useless in grammar: opt_distinct_clause [-Wother]
>       opt_distinct_clause:
>       ^~~~~~~~~~~~~~~~~~~
> 
> I only see it when I do a "make maintainer-clean" before the make
> because "make clean" does not remove preproc.y.

Sorry, this is Bison version 3.3.2, included in Debian 10.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  The usefulness of a cup is in its emptiness, Bruce Lee