Re: JIT doing duplicative optimization?

From: Andres Freund <andres(at)anarazel(dot)de>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Pg Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: JIT doing duplicative optimization?
Date: 2021-11-15 17:18:27
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On 2021-11-14 18:46:34 -0500, Tom Lane wrote:
> BTW, I realized while working on this that I have little idea what the
> "Functions:" count is. Nor does our documentation explain that (or any
> other of these numbers), at least not anywhere I could find. That seems
> like a pretty serious documentation fail.

It's literally the number of functions created in the JIT code. That could be
functions for evaluating one expression, or functions for deforming tuples of
one type of tupledesc. It's the simplest measure of "amount of JITed stuff" I
could find. I'd proposed a more detailed explain option where we'd optionally
print details about what exactly is JITed where a while back, but there were
some explain output format challenges...

> If these numbers aren't important enough to explain in the docs, why are we
> printing them at all?

Afaict we don't have detailed docs for EXPLAIN output in general?


Andres Freund

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