Re: pg_stat_statements and "IN" conditions - Mailing list pgsql-hackers

From Álvaro Herrera
Subject Re: pg_stat_statements and "IN" conditions
Date
Msg-id 202503031156.uoruitdjdwfr@alvherre.pgsql
Whole thread Raw
In response to Re: pg_stat_statements and "IN" conditions  (Sami Imseih <samimseih@gmail.com>)
Responses Re: pg_stat_statements and "IN" conditions
Re: pg_stat_statements and "IN" conditions
List pgsql-hackers
On 2025-Feb-18, Sami Imseih wrote:

> > It's not a question about whether it's possible to implement this,
> > but about whether it makes sense. In case of plain constants it's
> > straightforward -- they will not change anything meaningfully and
> > hence could be squashed from the query. Now for a function, that
> > might return different values for the same set of constant
> > arguments, it's much less obvious and omitting such expressions
> > might have unexpected consequences.
> 
> query jumbling should not care about the behavior of the function. If
> we take a regular call to a volatile function, we will generate the
> same queryId for every call regardless of the input to the function.
> Why does the in-list case need to care about the volatility of the
> function?

I feel quite insecure about this idea TBH.  At least with immutable
functions I don't expect the system to behave wildly different than with
actual constants.  What non-immutable functions do you have in mind that
would be useful to fold as if they were constants in the IN list in such
a query?

In the meantime, here's v28 which is Dmitry's v27 plus pgindent.  No
other changes.  Dmitry, were you planning to submit a new version?

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
"The problem with the future is that it keeps turning into the present"
(Hobbes)

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