Horton

Re: pg_stat_statements and "IN" conditions

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Dmitry Dolgov <9erthalion6@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, 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>
Date: 2022-03-14T15:02:16Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Introduce squashing of constant lists in query jumbling

  2. Make documentation builds reproducible

  3. Include values of A_Const nodes in query jumbling

  4. Teach planner about more monotonic window functions

  5. Split up guc.c for better build speed and ease of maintenance.

On Mon, Mar 14, 2022 at 10:57 AM Dmitry Dolgov <9erthalion6@gmail.com> wrote:
> Well, yeah, the commit message is somewhat clumsy in this regard. It
> works almost in the way you've described, except if the list is all
> constants and long enough to satisfy the threshold then *first N
> elements (where N == threshold) will be jumbled -- to leave at least
> some traces of it in pgss.

But that seems to me to be a thing we would not want. Why do you think
otherwise?

> I'm not sure if I follow the last point. WHERE x in (1,3) and x =
> any(array[1,3]) are two different things for sure, but in which way are
> they going to be mixed together because of this change? My goal was to
> make only the following transformation, without leaving any uncertainty:
>
> WHERE x in (1, 2, 3, 4, 5) -> WHERE x in (1, 2, ...)
> WHERE x = any(array[1, 2, 3, 4, 5]) -> WHERE x = any(array[1, 2, ...])

I understand. I think it might be OK to transform both of those
things, but I don't think it's very clear either from the comments or
the nonexistent documentation that both of those cases are affected --
and I think that needs to be clear. Not sure exactly how to do that,
just saying that we can't add behavior unless it will be clear to
users what the behavior is.

> Sure, I'll add documentation. To be honest I'm not targeting PG15 with
> this, just want to make some progress.

wfm!

-- 
Robert Haas
EDB: http://www.enterprisedb.com