Date: Tue, 27 Dec 2022 09:16:31 -0600
From: Justin Pryzby <pryzby@telsasoft.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
	pgsql-hackers@postgresql.org
Subject: Re: Underscores in numeric literals
Message-ID: <20221227151631.GV1153@telsasoft.com>
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On Tue, Dec 27, 2022 at 09:55:32AM -0500, Tom Lane wrote:
> Peter Eisentraut <peter.eisentraut@enterprisedb.com> writes:
> > Here is a patch to add support for underscores in numeric literals, for 
> > visual grouping, like
> 
> >      1_500_000_000
> >      0b10001000_00000000
> >      0o_1_755
> >      0xFFFF_FFFF
> >      1.618_034
> 
> > per SQL:202x draft.
> 
> > This adds support in the lexer as well as in the integer type input 
> > functions.
> > TODO: float/numeric type input support
> 
> Hmm ... I'm on board with allowing this in SQL if the committee says
> so.

> I'm not especially on board with accepting it in datatype input
> functions.  There's been zero demand for that AFAIR.  Moreover,
> I don't think we need the inevitable I/O performance hit, nor the
> increased risk of accepting garbage, nor the certainty of
> inconsistency with other places that don't get converted (because
> they depend on strtoul() or whatever).

+1 to accept underscores only in literals and leave input functions
alone.

(When I realized that python3.6 changed to accept things like
int("3_5"), I felt compelled to write a wrapper to check for embedded
underscores and raise an exception in that case.  And I'm sure it
affected performance.)

-- 
Justin