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From: Richard Guo <[email protected]>
To: David Rowley <[email protected]>
Cc: Andrei Lepikhov <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Subject: Re: Memoize ANTI and SEMI JOIN inner
Date: Mon, 31 Mar 2025 18:03:43 +0900
Message-ID: <CAMbWs4_qE=j=KQ3bs8ryLCe4OPYbSaT+2RAVUaoj6vvxKrQDiQ@mail.gmail.com> (raw)
In-Reply-To: <CAApHDvr2NRbjLXEUXvvKNCDcHfhC6UBL6ZmJzXZ29MBPi3+y8g@mail.gmail.com>
References: <[email protected]>
	<[email protected]>
	<CAApHDvr2NRbjLXEUXvvKNCDcHfhC6UBL6ZmJzXZ29MBPi3+y8g@mail.gmail.com>

On Thu, Mar 20, 2025 at 3:02 PM David Rowley <[email protected]> wrote:
> For making this work, I think the attached should be about the guts of
> the code changes. I didn't look at the comments. Right now I can't
> think of any reason why this can't be done, but some experimentation
> might reveal some reason that it can't.

I reviewed this patch and I have some concerns about the following
code:

    if (extra->inner_unique &&
        (inner_path->param_info == NULL ||
         bms_num_members(inner_path->param_info->ppi_serials) <
         list_length(extra->restrictlist)))
        return NULL;

I understand that this check is used to ensure that the entire join
condition is parameterized in the case of unique joins, so that we can
safely mark the cache entry as complete after reading the first tuple.
However, ppi_clauses includes join clauses available from all outer
rels, not just the current outer rel, while extra->restrictlist only
includes the restriction clauses for the current join.  This means the
check could pass even if a restriction clause isn't parameterized, as
long as another join clause, which doesn't belong to the current join,
is included in ppi_clauses.

Thanks
Richard

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