From: Andrew Gierth <andrew@tao11.riddles.org.uk>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Surafel Temesgen <surafel3000@gmail.com>,
  Tomas Vondra <tomas.vondra@2ndquadrant.com>,
  PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: FETCH FIRST clause WITH TIES option
In-Reply-To: <20200407203654.GA15931@alvherre.pgsql> (Alvaro Herrera's message
	of "Tue, 7 Apr 2020 16:36:54 -0400")
Message-ID: <87a73mn4cl.fsf@news-spur.riddles.org.uk>
References: <20200407203654.GA15931@alvherre.pgsql>
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Date: Wed, 08 Apr 2020 03:01:33 +0100
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>>>>> "Alvaro" == Alvaro Herrera <alvherre@2ndquadrant.com> writes:

 Alvaro> It turns out that the SQL standard is much more limited in what
 Alvaro> it will accept there. But our grammar (what we'll accept for
 Alvaro> the ancient LIMIT clause) is very lenient -- it'll take just
 Alvaro> any expression. I thought about reducing that to NumericOnly
 Alvaro> for FETCH FIRST .. WITH TIES, but then I have to pick: 1)
 Alvaro> gram.y fails to compile because of a reduce/reduce conflict, or
 Alvaro> 2) also restricting FETCH FIRST .. ONLY to NumericOnly. Neither
 Alvaro> of those seemed very palatable.

FETCH FIRST ... ONLY was made _too_ restrictive initially, such that it
didn't allow parameters (which are allowed by the spec); see 1da162e1f.

(That change didn't present a problem for ruleutils, because FETCH FIRST
... ONLY is output as a LIMIT clause instead.)

This needs to be fixed in ruleutils, IMO, not by changing what the
grammar accepts.

-- 
Andrew.