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From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: legrand legrand <legrand_legrand@hotmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: explain plans with information about (modified) gucs
Date: Tue, 1 Jan 2019 20:11:34 +0100
Message-ID: <0025cff2-a40f-0226-1cbb-2d52295541a9@2ndquadrant.com> (raw)
In-Reply-To: <CAFj8pRCEZhVc3i8UEGhT9xUYMAY_MqZSYVo4s18K1hB=zNHK0A@mail.gmail.com>
References: <e1791b4c-df9c-be02-edc5-7c8874944be0@2ndquadrant.com>
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	<2c09fe19-e4a0-ea66-5a7f-e69d46420e28@2ndquadrant.com>
	<20181217234353.fde7vityxvoullil@alap3.anarazel.de>
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	<CAFj8pRCEZhVc3i8UEGhT9xUYMAY_MqZSYVo4s18K1hB=zNHK0A@mail.gmail.com>



On 1/1/19 6:48 PM, Pavel Stehule wrote:
> 
> 
> út 1. 1. 2019 v 18:39 odesílatel Tomas Vondra
> <tomas.vondra@2ndquadrant.com <mailto:tomas.vondra@2ndquadrant.com>> napsal:
> 
>     Attached is v4, changing how GUCs are picked for inclusion on the query
>     plans. Instead of picking the GUCs based on group and/or explicitly, a
>     new GUC_EXPLAIN flag is used for that.
> 
>     I went through GUCs defined in guc.c and marked those in QUERY_TUNING*
>     groups accordingly, with the exception of default_statistics_target
>     because that seems somewhat useless without showing the value used to
>     actually analyze the table (and/or columns).
> 
>     I've also included a couple of other GUCs, that I find to be relevant:
> 
>     - parallel_leader_participation
>     - max_parallel_workers_per_gather
>     - max_parallel_workers
>     - search_path
>     - effective_io_concurrency
>     - work_mem
>     - temp_buffers
>     - plan_cache_mode
> 
> 
> when plan_cache_mode is auto, you know maybe too less executed query.
> Maybe you can read somewhere if plan was custom or generic.
> 

This patch is about showing GUCs, not such additional internal info.
Also, you'll see the plan actually used.

> 
>     I think this covers the interesting GUCs pretty well, although perhaps I
>     missed something.
> 
> 
> seq_page_cost, random_page_cost, from_collapse_limit,
> join_collapse_limit, ... enable_***
> 

All these GUCs are included, of course.



-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services




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