Date: Thu, 9 Feb 2023 16:02:38 +0100
From: Dmitry Dolgov <9erthalion6@gmail.com>
To: Sergei Kornilov <sk@zsrv.org>
Cc: Michael Paquier <michael@paquier.xyz>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>,
	Marcos Pegoraro <marcos@f10.com.br>,
	vignesh C <vignesh21@gmail.com>,
	Robert Haas <robertmhaas@gmail.com>, Zhihong Yu <zyu@yugabyte.com>,
	David Steele <david@pgmasters.net>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>,
	Greg Stark <stark@mit.edu>,
	Pavel Trukhanov <pavel.trukhanov@gmail.com>,
	Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: pg_stat_statements and "IN" conditions
Message-ID: <20230209150238.rdtwruh5i34hdag5@ddolgov.remote.csb>
References: <20230129133219.tpuzqbyqw3ojztbd@erthalion.local>
 <20230202140727.g7tw7qjo43g54wcb@alvherre.pgsql>
 <20230202150554.dwxhvw23epcskppb@ddolgov.remote.csb>
 <20230204170841.xfgxoo7ymwbvu7yx@erthalion.local>
 <Y98GsRJoCM4RrcWp@paquier.xyz>
 <20230205113346.gmbf5ycnukuhnmqa@erthalion.local>
 <2420105.1675612952@sss.pgh.pa.us>
 <20230205195600.e3bhwszzm5kdyyxl@erthalion.local>
 <966631675800892@znolar4klagewshm.sas.yp-c.yandex.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <966631675800892@znolar4klagewshm.sas.yp-c.yandex.net>
Archived-At: <https://www.postgresql.org/message-id/20230209150238.rdtwruh5i34hdag5%40ddolgov.remote.csb>
Precedence: bulk

> On Tue, Feb 07, 2023 at 11:14:52PM +0300, Sergei Kornilov wrote:
> Hello!

Thanks for reviewing.

> Unfortunately, rebase is needed again due to recent changes in queryjumblefuncs ( 9ba37b2cb6a174b37fc51d0649ef73e56eae27fc )

Yep, my favourite game, rebaseball. Will post a new version soon, after
figuring out all the recent questions.

> It seems a little strange to me that with const_merge_threshold = 1, such a test case gives the same result as with const_merge_threshold = 2
>
> select pg_stat_statements_reset();
> set const_merge_threshold to 1;
> select * from test where i in (1,2,3);
> select * from test where i in (1,2);
> select * from test where i in (1);
> select query, calls from pg_stat_statements order by query;
>
>                 query                | calls
> -------------------------------------+-------
>  select * from test where i in (...) |     2
>  select * from test where i in ($1)  |     1
>
> Probably const_merge_threshold = 1 should produce only "i in (...)"?

Well, it's not intentional, probably I need to be more careful with
off-by-one. Although I agree to a certain extent with Peter questioning
the value of having numerical option here, let me think about this.

> const_merge_threshold is "the minimal length of an array" (more or equal) or "array .. length is larger than" (not equals)? I think the documentation is ambiguous in this regard.
>
> I also noticed a typo in guc_tables.c: "Sets the minimal numer of constants in an array" -> number

Yep, I'll rephrase the documentation.