Date: Thu, 6 Jan 2022 11:35:14 +0800
From: Julien Rouhaud <rjuju123@gmail.com>
To: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>,
	Daniel Verite <daniel@manitou-mail.org>
Subject: Re: ICU for global collation
Message-ID: <YdZjctLaTLthqpOA@jrouhaud>
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On Tue, Jan 04, 2022 at 05:03:10PM +0100, Peter Eisentraut wrote:
> On 04.01.22 03:21, Julien Rouhaud wrote:
> 
> > > -	if (!lc_collate_is_c(collid) && collid != DEFAULT_COLLATION_OID)
> > > -		mylocale = pg_newlocale_from_collation(collid);
> > > +	if (!lc_collate_is_c(collid))
> > > +	{
> > > +		if (collid != DEFAULT_COLLATION_OID)
> > > +			mylocale = pg_newlocale_from_collation(collid);
> > > +		else if (default_locale.provider == COLLPROVIDER_ICU)
> > > +			mylocale = &default_locale;
> > > +	}
> > 
> > There are really a lot of places with this new code.  Maybe it could be some
> > new function/macro to wrap that for the normal case (e.g. not formatting.c)?
> 
> Right, we could just put this into pg_newlocale_from_collation(), but the
> comment there says
> 
>  * In fact, they shouldn't call this function at all when they are dealing
>  * with the default locale.  That can save quite a bit in hotspots.
> 
> I don't know how to assess that.
> 
> We could pack this into a macro or inline function if we are concerned about
> this.

Yes that was my idea, just have a new function (inline function or a macro
then since pg_newlocale_from_collation() clearly warns about performance
concerns) that have the whole
is-not-c-collation-and-is-default-collation-or-icu-collation logic and calls
pg_newlocale_from_collation() only when needed.