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Re: Tightening selection of default sort/group operators

From: Peter Eisentraut <peter_e(at)gmx(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: Tightening selection of default sort/group operators
Date: 2002-11-30 00:37:30
Message-ID: Pine.LNX.4.44.0211300129290.12428-100000@localhost.localdomain (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane writes:

> What I'm thinking of doing instead is always looking up the "=" operator
> by name, and accepting this as actually being equality if it is marked
> mergejoinable or hashjoinable or has eqsel() as its restriction
> selectivity estimator (oprrest).  If we are looking for a "<" operator
> to implement sorting/grouping, then we require "=" to be mergejoinable,
> and we use its lsortop operator (regardless of name).

My first thought is that this seems to be an awefully backwards way to
define operator semantic metadata.  I think we either have to flag
operators explicitly ("this is the less-than operator"), or we just
require that < <= = >= > have certain semantics.  I could be happy with
both.

-- 
Peter Eisentraut   peter_e(at)gmx(dot)net


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