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

From: Lukas Fittl <lukas(at)fittl(dot)com>
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: 2018-10-01 07:32:18
Message-ID: CAP53PkxmgJht69pabxBXJBM+0oc6kf3KHMborLP7H2ouJ0CCtQ@mail.gmail.com
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On Tue, Sep 25, 2018 at 1:17 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> I've pushed the change without that bit - it's just a few additional
> lines if we want to change that.
>

It seems that since this commit, JIT statistics are now only being printed
for parallel query plans. This is due to ExplainPrintJIT being called
before ExecutorEnd, so in a non-parallel query,
queryDesc->estate->es_jit_combined_instr will never get set.

Attached a patch that instead introduces a new ExplainPrintJITSummary
method that summarizes the statistics before they get printed.

I've also removed an (I believe) unnecessary "if (estate->es_instrument)"
check that prevented EXPLAIN without ANALYZE from showing whether JIT would
be used or not.

In addition this also updates a missed section in the documentation with
the new stats output format.

Best,
Lukas

--
Lukas Fittl

Attachment Content-Type Size
fix-jit-statistics-in-EXPLAIN-for-non-parallel-queries-v1.patch application/octet-stream 5.2 KB

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