Date: Thu, 21 Mar 2024 19:51:39 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@lists.postgresql.org, alex work <alexwork033@gmail.com>,
	Robert Haas <robertmhaas@gmail.com>
Subject: Re: Slow GRANT ROLE on PostgreSQL 16 with thousands of ROLEs
Message-ID: <20240322005139.GA2060816@nathanxps13>
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On Thu, Mar 21, 2024 at 03:40:12PM -0500, Nathan Bossart wrote:
> On Thu, Mar 21, 2024 at 04:31:45PM -0400, Tom Lane wrote:
>> I don't think we have any really cheap way to de-duplicate the role
>> OIDs, especially seeing that it has to be done on-the-fly within the
>> collection loop, and the order of roles_list is at least potentially
>> interesting.  Not sure how to make further progress without a lot of
>> work.
> 
> Assuming these are larger lists, this might benefit from optimizations
> involving SIMD intrinsics.  I looked into that a while ago [0], but the
> effort was abandoned because we didn't have any concrete use-cases at the
> time.  (I'm looking into some additional optimizations in a separate thread
> [1] that would likely apply here, too.)

Never mind.  With the reproduction script, I'm only seeing a ~2%
improvement with my patches.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com