Date: Mon, 10 Jan 2022 18:39:57 +0800
From: Julien Rouhaud <rjuju123@gmail.com>
To: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: Multiple Query IDs for a rewritten parse tree
Message-ID: <YdwM/SIuhP92omGi@jrouhaud>
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On Mon, Jan 10, 2022 at 03:24:46PM +0500, Andrey Lepikhov wrote:
> On 10/1/2022 13:56, Julien Rouhaud wrote:
> > 
> > I don't know the details of that extension, but I think that it should work as
> > long as you have the constants information in the jumble state, whatever the
> > resulting normalized query string is right?
> Yes. the same input query string doesn't prove that frozen query plan can be
> used, because rewrite rules could be changed. So we use only a query tree.

Yes, I'm fully aware of that.  I wasn't asking about using the input query
string but the need for generating a dedicated normalized output query string
that would be potentially different from the one generated by
pg_stat_statements (or similar).

> > But then, if generating 2 queryid is a better for performance, does the
> > extension really need an additional jumble state and/or normalized query
> > string?
> Additional Jumble state isn't necessary, but it would be better for
> performance to collect pointers to all constant nodes during a process of
> hash generation.

I agree, but it's even better for performance if this is collected only once.
I still don't know if this extension (or any extension) would require something
different from a common jumble state that would serve for all purpose or if we
can work with a single jumble state and only handle multiple queryid.