Re: extend pgbench expressions with functions

From: Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
To: coelho(at)cri(dot)ensmp(dot)fr
Cc: robertmhaas(at)gmail(dot)com, pgsql-hackers(at)postgresql(dot)org
Subject: Re: extend pgbench expressions with functions
Date: 2015-11-04 06:33:46
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Hello, sorry for the silence.

At Fri, 18 Sep 2015 20:35:48 +0200 (CEST), Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> wrote in <alpine(dot)DEB(dot)2(dot)10(dot)1509182019100(dot)27223(at)sto>
> > -1. double is an inexact type, whereas integer is an exact type.
> Sure. I already argue on that very line.


> > The typical way to handle this sort of thing is to define a struct
> > whose first member is a type field and whose second field is a union
> > of all the types you need to care about.
> Yep.
> > Then that gets passed around everywhere. This patch should be
> > designed in such a way that if we eventually end up with functions
> > that have 10 different return types instead of 2 different return
> > types, we don't need to add 8 more parameters to any functions.
> > Instead, those still return PgBench_Value (or whatever we call it)
> > which is the aforementioned struct, but there are more options for
> > what that can contain.
> I just put the double type as a proof of concept, but for pgbench only
> integers really matters.
> What you suggest would work, but it would also result in ugly and
> lengthy code, as I argued in another mail, because you have to decide
> for overloaded operators and functions which actual typed operator
> must be called, and then perform the necessary type conversions
> depending on the actual type of the operands. The implicit descendent
> typing used in the patch hides this, and is more than enough for
> pgbench, IMO.

I also agree this.

> If this is a blocker, I would rather remove the support for doubles
> than write verbose and inelegant code.

I understood the situation and agreed for current shape of the
code. I no longer object the calling-alternatively code. But I'd
like see the abbreviated discussion in the comment on the


Kyotaro Horiguchi
NTT Open Source Software Center

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