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From: John Naylor <johncnaylorls@gmail.com>
Date: Tue, 13 Jan 2026 18:38:51 +0700
Message-ID: <CANWCAZZgKnf8dNOd_w03n88NqOfmMnMv2=D8_Oy6ADGyiMq+cg@mail.gmail.com>
Subject: Re: pg_plan_advice
To: Robert Haas <robertmhaas@gmail.com>
Cc: Lukas Fittl <lukas@fittl.com>, Jacob Champion <jacob.champion@enterprisedb.com>, 
	Dian Fay <di@nmfay.com>, Matheus Alcantara <matheusssilv97@gmail.com>, 
	Jakub Wartak <jakub.wartak@enterprisedb.com>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Tue, Jan 13, 2026 at 12:14=E2=80=AFAM Robert Haas <robertmhaas@gmail.com=
> wrote:
> Here's v9. Changes:

This is perhaps the least interesting part of 0005, but since I
committed this API, I thought I'd chime in:

+ /* alias_name may not be NULL */
+ sp_len =3D fasthash_accum_cstring(&hs, key.alias_name);
+
+ /* partition_name and plan_name, however, can be NULL */
+ if (key.partition_name !=3D NULL)
+ sp_len +=3D fasthash_accum_cstring(&hs, key.partition_name);
+ if (key.plan_name !=3D NULL)
+ sp_len +=3D fasthash_accum_cstring(&hs, key.plan_name);

It looks like it would be helpful if fasthash_accum_cstring just
returned zero when given a NULL string, as in the attached. We could
also do something like add a large number to the hash, but I'm not
sure that's necessary.

+ /*
+ * hashfn_unstable.h recommends using string length as tweak. It's not
+ * clear to me what to do if there are multiple strings, so for now I'm
+ * just using the total of all of the lengths.
+ */
+ return fasthash_final32(&hs, sp_len);

Sounds reasonable, so the patch also documents that.

--
John Naylor
Amazon Web Services

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