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From: Sami Imseih <[email protected]>
To: Julien Rouhaud <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: [email protected]
Subject: Re: Cleaning up PREPARE query strings?
Date: Thu, 15 Jan 2026 13:13:36 -0600
Message-ID: <CAA5RZ0sHJ2D2vdhH4nnUVuZKfSqpaywPeP98C9-LkGKG2rPSYg@mail.gmail.com> (raw)
In-Reply-To: <aWhv-ZXEJ3kd-dWa@jrouhaud>
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> I only had a quick look at the code but unless I'm missing something it's
> mostly an oversight as I pass "new_query" to CreateCachedPlan() but still pass
> the original query string to pg_analyze_and_rewrite_varparams().  Using
> "new_query" there too should fix the problem?

That will be a fix, but that seems way too invasive for me. Not sure if it may
break other things.

> > I am thinking that storing the statement length and location in the entry
> > of prepared_queries may be the better option. Having that info, the
> > cleaned up query text can be generated on the fly whenever
> > pg_prepared_statement is called.
>
> I don't like this approach as it has more execution time overhead, but also
> doesn't fix at all the memory waste in the prepared statements cache.

ISTM that your proposal will actually use more memory because
pstate->p_sourcetext does not get free'd, but we must now allocate
space for a new "cleaned" query.

As far as execution overhead, this will only be paid when you query
pg_prepared_statement, and we can even optimize this a bit by only
cleaning once and reusing the results.

> FWIW I think that this should belong to pg_stat_statements testing, no the main
> regression tests.  This would also ensure that we see consistent results in
> some other scenarios.

I agree.

--
Sami Imseih
Amazon Web Services (AWS)

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