Re: Query is over 2x slower with jit=on

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com>, Andreas Joseph Krogh <andreas(at)visena(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, "Jonathan S(dot) Katz" <jkatz(at)postgresql(dot)org>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Query is over 2x slower with jit=on
Date: 2018-09-20 03:26:52
Message-ID: 11291.1537414012@sss.pgh.pa.us
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Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2018-09-17 17:50:15 -0400, Tom Lane wrote:
>> Just to throw a contrarian opinion into this: I find the current EXPLAIN
>> output for JIT to be insanely verbose already.

> Hm, it'd have been nice to get that feedback a little bit earlier, I did
> inquire...

> Currently:

> JIT:
> Functions: 2
> Generation Time: 0.680 ms
> Inlining: true
> Inlining Time: 7.591 ms
> Optimization: true
> Optimization Time: 20.522 ms
> Emission Time: 14.607 ms

Just to clarify, that seems perfectly fine for the "machine readable"
output formats. I'd just like fewer lines in the "human readable"
output.

> How about making that:

> JIT:
> Functions: 2
> Options: Inlining, Optimization
> Times (Total, Generation, Inlining, Optimization, Emission): 43.4 ms, 0.680 ms, 7.591 ms, 20.522 ms, 14.607 ms

> or something similar?

That's going in the right direction. Personally I'd make the last line
more like

Times: generation 0.680 ms, inlining 7.591 ms, optimization 20.522 ms, emission 14.607 ms, total 43.4 ms

(total at the end seems more natural to me, YMMV). Also, the "options"
format you suggest here seems a bit too biased towards binary on/off
options --- what happens when there's a three-way option? So maybe that
line should be like

Options: inlining on, optimization on

though I'm less sure about that part.

regards, tom lane

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