Re: Polyphase merge is obsolete

From: Peter Geoghegan <pg(at)bowt(dot)ie>
To: John Naylor <john(dot)naylor(at)enterprisedb(dot)com>
Cc: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Jaime Casanova <jcasanov(at)systemguards(dot)com(dot)ec>, vignesh C <vignesh21(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Subject: Re: Polyphase merge is obsolete
Date: 2021-10-05 21:44:37
Message-ID: CAH2-WzmJvFOZb+P=xAh2fK4tK2ad86r2A2q_rdq4QaXKAfwifw@mail.gmail.com
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On Tue, Oct 5, 2021 at 10:25 AM John Naylor
<john(dot)naylor(at)enterprisedb(dot)com> wrote:
> int64 is used elsewhere in this file, and I see now reason to do otherwise.

Right. The point of using int64 in tuplesort.c is that the values may
become negative in certain edge-cases. The whole LACKMEM() concept
that tuplesort.c uses to enforce work_mem limits sometimes allows the
implementation to use slightly more memory than theoretically
allowable. That's how we get negative values.

--
Peter Geoghegan

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