Re: sortsupport for text

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Peter Geoghegan <peter(at)2ndquadrant(dot)com>
Cc: Greg Stark <stark(at)mit(dot)edu>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: sortsupport for text
Date: 2012-06-17 16:50:09
Message-ID: 27373.1339951809@sss.pgh.pa.us
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Peter Geoghegan <peter(at)2ndquadrant(dot)com> writes:
> On 17 June 2012 17:01, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> The killer reason why it must be like that is that you can't use hash
>> methods on text if text equality is some unknown condition subtly
>> different from bitwise equality.

> Fair enough, but I doubt that we need to revert the changes made in
> this commit to texteq in addition to the changes I'd like to see in
> order to be semantically self-consistent. That is because there is
> often a distinction made between equality and equivalence, and we
> could adopt this distinction.

How exactly do you plan to shoehorn that into SQL? You could invent
some nonstandard "equivalence" operator I suppose, but what will be the
value? We aren't going to set things up in such a way that we can't
use hash join or hash aggregation in queries that use the regular "="
operator. IMO there just aren't going to be enough people who care to
use a non-default operator.

regards, tom lane

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