From: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix dynahash's HASH_FIXED_SIZE ("isfixed") option.
Date: Fri, 25 Jul 2025 14:57:04 +0000
Message-ID: <E1ufJr6-000gqE-1i@gemulon.postgresql.org> (raw)
Fix dynahash's HASH_FIXED_SIZE ("isfixed") option.
This flag was effectively a no-op in EXEC_BACKEND (ie, Windows)
builds, because it was kept in the process-local HTAB struct,
and it could only ever become set in the postmaster's copy.
The simplest fix is to move it to the shared HASHHDR struct.
We could keep a copy in HTAB as well, as we do with keysize
and some other fields, but the "too much contention" argument
doesn't seem to apply here: we only examine isfixed during
element_alloc(), which had better not get hit very often for
a shared hashtable.
This oversight dates to 7c797e719 which invented the option.
But back-patching doesn't seem appropriate given the lack of
field complaints. If there is anyone running an affected
workload on Windows, they might be unhappy about the behavior
changing in a minor release.
Author: Aidar Imamov <a.imamov@postgrespro.ru>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/4d0cb35ff01c5c74d2b9a582ecb73823@postgrespro.ru
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/5457ea46d181f8b8dbe1ae482720b23bff4029de
Modified Files
--------------
src/backend/utils/hash/dynahash.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: tgl@sss.pgh.pa.us, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix dynahash's HASH_FIXED_SIZE ("isfixed") option.
In-Reply-To: <E1ufJr6-000gqE-1i@gemulon.postgresql.org>
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