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From: Tom Lane <[email protected]>
To: Nathan Bossart <[email protected]>
Cc: [email protected]
Cc: alex work <[email protected]>
Cc: Robert Haas <[email protected]>
Subject: Re: Slow GRANT ROLE on PostgreSQL 16 with thousands of ROLEs
Date: Mon, 25 Mar 2024 11:08:39 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <20240325144743.GA2618709@nathanxps13>
References: <20240322005139.GA2060816@nathanxps13>
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Nathan Bossart <[email protected]> writes:
> Are there any changes you'd like to see for the Bloom patch [0]?  I'd like
> to see about getting that committed for v17.  One thing that crossed my
> mind is creating a combined list/filter that transparently created a filter
> when necessary (for reuse elsewhere), but I'm not sure that's v17 material.

Yeah, that thought occurred to me too, but I think we ought to have a
few more use-cases in view before trying to write an API.

As for the patch, I agree it could go into v17, but I think there is
still a little bit of work to do:

* The magic constants (crossover list length and bloom filter size)
need some testing to see if there are better values.  They should
probably be made into named #defines, too.  I suspect, with little
proof, that the bloom filter size isn't particularly critical --- but
I know we pulled the crossover of 1000 out of thin air, and I have
no certainty that it's even within an order of magnitude of being a
good choice.

* Code needs more than zero comments.

* Is it worth trying to make a subroutine, or at least a macro,
so as not to have 2 copies of the code?

			regards, tom lane

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