On 28/2/2024 04:19, Tom Lane wrote:
Andrei Lepikhov <a.lepik...@postgrespro.ru> writes:
IMO, the routine eval_const_expressions_mutator contains some stale code:
I'd like to push back against the idea that eval_const_expressions
is expected to return a freshly-copied tree. Its API specification
contains no such claim. It's true that it appears to do that
everywhere but here, but I think that's an implementation detail
that callers had better not depend on. It's not hard to imagine
someone trying to improve its performance by avoiding unnecessary
copying.
Thanks for the explanation. I was just such a developer of extensions
who had looked into the internals of the eval_const_expressions, found a
call for a '_mutator' function, and made such a mistake :).
I agree that freeing the return node value doesn't provide a sensible
benefit because the underlying bushy tree was copied during mutation.
What's more, it makes even less sense with the selectivity context
coming shortly (I hope).
--
regards,
Andrei Lepikhov
Postgres Professional
