Horton

Re: Memoize ANTI and SEMI JOIN inner

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Richard Guo <guofenglinux@gmail.com>
Cc: Andrei Lepikhov <lepihov@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2025-03-31T09:39:14Z
Lists: pgsql-hackers

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  1. Enable use of Memoize for ANTI joins

On Mon, 31 Mar 2025 at 22:03, Richard Guo <guofenglinux@gmail.com> wrote:
> 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.

Shouldn't you be more concerned about master here than the patch given
that the code you pasted is from master?

David