From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
---|---|
To: | Elvis Pranskevichus <elprans(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org> |
Subject: | Re: BUG #17213: Wrong result from a query involving Merge Semi Join and Memoize |
Date: | 2021-11-22 10:36:25 |
Message-ID: | CAApHDvrnnHYyjQS4+wtDDiQMwHyPQtK_xWpspb6CqdfZhk+J-Q@mail.gmail.com |
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Lists: | pgsql-bugs |
On Tue, 26 Oct 2021 at 20:50, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> An alternative way to fix the problem would be just to flush the cache
> whenever a Param changes that is not part of the cache key. The
> Materalize node works a bit like this, except it'll just flush the
> cache whenever a param changes, since the Material cache is not
> parameterized. One fairly hefty drawback with doing it this way is
> that the planner does not get a chance to take into account the fact
> that the cache could be flushed quite often. This could result in a
> Nested Loop / Memoize join being chosen instead of a Hash or Merge
> Join when the hash or merge join would be much more favourable. Let's
> call this "option 2".
I'm planning on giving the patch I submitted another look with the
intention of pushing it tomorrow.
David
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