| From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Richard Guo <guofenglinux(at)gmail(dot)com> |
| Cc: | nikhil raj <nikhilraj474(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Significant Execution Time Difference Between PG13.14 and PG16.4 for Query on information_schema Tables. |
| Date: | 2024-08-27 23:03:08 |
| Message-ID: | CAApHDvp1mue1a5fdfsa2z2mAS6v2d9+kxMzxH7GhAiC0Z7o8Mw@mail.gmail.com |
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| Lists: | pgsql-general pgsql-hackers |
On Wed, 28 Aug 2024 at 09:52, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> The other problem with this is that it breaks one test case in
> memoize.sql: a query that formerly generated a memoize plan
> now does not use memoize. I am not sure why not --- does that
> mean anything to you?
The reason it works in master is that get_memoize_path() calls
extract_lateral_vars_from_PHVs() and finds PlaceHolderVars to use as
the Memoize keys. With your patch PlannerInfo.placeholder_list is
empty.
The commit that made this work is 069d0ff02. Richard might be able to
explain better. I don't quite understand why RelOptInfo.lateral_vars
don't contain these in the first place.
David
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