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From: David Mullineux <[email protected]>
To: Tom Lane <[email protected]>
Cc: Frédéric Yhuel <[email protected]>
Cc: Peter Eisentraut <[email protected]>
Cc: [email protected]
Subject: Re: Has gen_random_uuid() gotten much slower in v17?
Date: Tue, 26 Nov 2024 15:23:43 +0000
Message-ID: <CAGsyd8W8oB5YqcDB=BUUn32XWGbt8x0UYO_WAJHFGcgX076tXg@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CAGsyd8XBE7Ksq2Z75CTStrjSswOjVUE8S+i7qq1hGvYRj+_bcA@mail.gmail.com>
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On Wed, 20 Nov 2024, 22:26 Tom Lane, <[email protected]> wrote:

> [ please don't top-quote, it makes the conversation hard to follow ]
>
> David Mullineux <[email protected]> writes:
> > On Wed, 20 Nov 2024, 15:46 Tom Lane, <[email protected]> wrote:
> >> Yeah.  Also, are you building with openssl, or not?
>
> > No, not at all!
>
> If you're not using openssl, then gen_random_uuid basically devolves
> to a read of /dev/urandom.  Maybe you're using a different kernel
> than before, and it has different properties around that?
>
>                         regards, tom lane
>

Just to say, thanks Tom. You were dead right. From the code in
pg_strong_random.c
it looks like each call will do an open("/dev/urandom")

And that cannot be fast.

Not sure why,but I guess there are good reasons to not keep a file
descriptor to that device open across calls ?

Thanks anyway


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