Re: A modest proposal: make parser/rewriter/planner inputs read-only

From: Andrei Lepikhov <lepihov(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: A modest proposal: make parser/rewriter/planner inputs read-only
Date: 2025-04-16 07:28:31
Message-ID: 75a742bc-151e-4286-a2cc-01d0c26c1ffd@gmail.com
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On 4/15/25 19:34, Tom Lane wrote:
> Andrei Lepikhov <lepihov(at)gmail(dot)com> writes:
>> But what is the way you are proposing here? Do you mean that one more
>> entity will be explicitly introduced: a transformed parse tree?
>
> No, I wasn't thinking of adding new concepts, just saying that the
> inputs to certain operations need to be treated as read-only.
> What would you envision a "transformed parse tree" being that's not
> what we have today?
I just want to understand how your idea will work. The query_planner
does the job for subqueries separately. If a query is transformed in
some way (let's say, an unnecessary join is deleted), we need to change
references in the parse tree of another subquery, or it will not find
the reference at the moment of planning, right?

--
regards, Andrei Lepikhov

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