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From: Dmitry Dolgov <[email protected]>
To: Sergei Kornilov <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: Alvaro Herrera <[email protected]>
Cc: Marcos Pegoraro <[email protected]>
Cc: vignesh C <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Zhihong Yu <[email protected]>
Cc: David Steele <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Cc: Greg Stark <[email protected]>
Cc: Pavel Trukhanov <[email protected]>
Cc: Tom Lane <[email protected]>
Subject: Re: pg_stat_statements and "IN" conditions
Date: Thu, 9 Feb 2023 16:02:38 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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> 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.

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