Horton

Re: [PATCH] Introduce array_shuffle() and array_sample()

Martin Kalcher <martin.kalcher@aboutsource.net>

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From: Martin Kalcher <martin.kalcher@aboutsource.net>
To: Fabien COELHO <coelho@cri.ensmp.fr>
Cc: Dean Rasheed <dean.a.rasheed@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, Andrew Dunstan <andrew@dunslane.net>, John Naylor <john.naylor@enterprisedb.com>, Thomas Munro <thomas.munro@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-07-25T07:34:31Z
Lists: pgsql-hackers, pgsql-general

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Am 24.07.22 um 21:42 schrieb Fabien COELHO:
> 
> Duno. I'm still wondering what it should do. I'm pretty sure that the 
> documentation should be clear about a shared seed, if any. I do not 
> think that departing from the standard is a good thing, either.

Are sure it violates the standard? I could not find anything about it. 
The private prng state for random() was introduced in 2018 [0]. Neither 
commit nor discussion mentions any standard compliance.

[0] 
https://www.postgresql.org/message-id/E1gdNAo-00036g-TB%40gemulon.postgresql.org

I updated the documentation for setseed().

> If someone wants a limit, they can easily "LEAST(#1 dim size, other 
> limit)" to get it, it is easy enough with a strict function.

Convinced. It errors out now if n is out of bounds.

Martin

Commits

  1. Add array_sample() and array_shuffle() functions.

  2. Use a separate random seed for SQL random()/setseed() functions.