From: Tom Lane <tgl@sss.pgh.pa.us>
To: "Daniel Verite" <daniel@manitou-mail.org>
cc: "Peter Eisentraut" <peter.eisentraut@2ndquadrant.com>,
        "pgsql-hackers" <pgsql-hackers@postgresql.org>
Subject: Re: insensitive collations
In-reply-to: <39af4787-8042-4891-887c-3283488735db@manitou-mail.org>
References: <39af4787-8042-4891-887c-3283488735db@manitou-mail.org>
Comments: In-reply-to "Daniel Verite" <daniel@manitou-mail.org>
	message dated "Wed, 19 Dec 2018 13:06:29 +0100"
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Date: Wed, 19 Dec 2018 09:35:59 -0500
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"Daniel Verite" <daniel@manitou-mail.org> writes:
> To me it seems more natural to find a name for the other behavior, the
> one that consists of overwriting the locale-sensitive equality with
> the result of the byte-wise comparison. AFAIU the flag is meant
> to say: "don't do that".

> Some ideas that come to mind:

> as an enum
>  CREATE COLLATION ... ( [EQUALITY = 'natural' | 'bytewise' ] )
> as a boolean
>  CREATE COLLATION ... ( [NATURAL_EQUALITY = true | false ] )
>   defaulting to false
> or
>  CREATE COLLATION ... ( [BYTEWISE_EQUALITY = true | false ] )
>   defaulting to true

I don't really find it "natural" for equality to consider obviously
distinct values to be equal.  As a counterexample, the fact that IEEE
arithmetic treats 0 and -0 as equal seems to cause about as many problems
as it solves, and newcomers to float math certainly don't find it
"natural".  So I object to that particular naming.  Perhaps we could
do something around "uniqueness"?  That is, collations could have
a boolean property UNIQUE, default true, or something like that.

			regards, tom lane