Re: pgsql: Add documentation for the JIT feature.

From: Andres Freund <andres(at)anarazel(dot)de>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: pgsql: Add documentation for the JIT feature.
Date: 2018-03-29 18:01:16
Message-ID: 20180329180116.xvselrjpzk5fjul5@alap3.anarazel.de
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On 2018-03-29 13:26:31 -0400, Robert Haas wrote:
> On Thu, Mar 29, 2018 at 9:44 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > I'd go a little further and drop "JIT" from user-facing documentation
> > altogether. Instead refer to the feature as "compilation of expressions"
> > or some such. JIT is just jargon. Plus, the timing of the compilation is
> > actually the least important property for our purpose.
>
> I agree that talking about JIT compilation (or just-in-time
> compilation) would be better than talking just about JIT, but refusing
> to mention JIT seems counter-productive to me. There are a lot of
> people who know what just-in-time compilation is and will not realize
> that "compilation of expressions" refers to any such technology. If
> you don't know what it is, you can Google it. Just typing "jit" into
> Google produces a stupid urban dictionary hit and then this:
> https://en.wikipedia.org/wiki/Just-in-time_compilation -- and that
> contains useful information that you'll never find if you search for
> "compilation of expressions".
>
> Also, in a way, you could argue that v10 already did "compilation of
> expressions". It didn't compile them to machine language, true, but
> it translated them into a form which is faster to execute, and which
> is at least arguably a form of bytecode. It's not going to be clear,
> even to an expert, that "compilation of expressions" means something
> other than that, but if you say JIT, then all of a sudden people know
> what we're talking about.
>
> I agree that JIT is jargon, but it's pretty commonly-used jargon.

Precisely this. I'm very strongly against just saying "expression
compilation", it's just too imprecise. As Robert mentions it could refer
to what we do in v10, it could refer to ahead of time compilation of PL
functions, and it doesn't include compiling tuple deforming. Nor will
it describe compiling sorting, copy or whatnot.

I'm very open however to replacing JITing with JIT compiling and smilar
substitutions.

Greetings,

Andres Freund

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