Horton

Re: pg_stat_statements and "IN" conditions

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Dmitry Dolgov <9erthalion6@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>
Date: 2022-03-14T15:23:17Z
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.

Robert Haas <robertmhaas@gmail.com> writes:
> On Mon, Mar 14, 2022 at 10:57 AM Dmitry Dolgov <9erthalion6@gmail.com> wrote:
>> 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.

We've transformed IN(...) to ANY(ARRAY[...]) at the parser stage for a
long time, and this has been visible to users of either EXPLAIN or
pg_stat_statements for the same length of time.  I doubt people are
going to find that surprising.  Even if they do, it's not the query
jumbler's fault.

I do find it odd that the proposed patch doesn't cause the *entire*
list to be skipped over.  That seems like extra complexity and confusion
to no benefit.

			regards, tom lane