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Re: [HACKERS] Re: IDENTITY/GENERATED v36 Re: Final version of IDENTITY/GENERATED patch

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Zoltan Boszormenyi <zb(at)cybertec(dot)at>, "Florian G(dot) Pflug" <fgp(at)phlo(dot)org>, Bruce Momjian <bruce(at)momjian(dot)us>, List pgsql-patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: [HACKERS] Re: IDENTITY/GENERATED v36 Re: Final version of IDENTITY/GENERATED patch
Date: 2007-04-17 13:57:28
Message-ID: 4624D248.7040502@dunslane.net (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Tom Lane wrote:
> The problem comes from cases like
>
> 	colname coltype DEFAULT 5! GENERATED ...
>
> Since b_expr allows postfix operators, it takes one more token of
> lookahead than we have to tell if the default expression is "5!"
> or "5!GENERATED ...".
>
> There are basically two ways to fix this:
>
> 1. Collapse GENERATED ALWAYS and GENERATED BY into single tokens
> using filtered_base_yylex.
>
> 2. Stop allowing postfix operators in b_expr.
>
>   

I can't think of any good reason why we need postfix operators at all. 
Plenty of languages do quite happily without them, and where they make 
some sense (e.g. in C) they do so because of their side effect, which 
doesn't seem relevant here.

So I vote for #2 unless it will break too much legacy stuff. You should 
always be able to replace "operand postop" with a function call anyway - 
it's arguably just syntactic sugar.

cheers

andrew

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