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: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, John Naylor <john.naylor@enterprisedb.com>, Thomas Munro <thomas.munro@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-07-18T22:52:47Z
Lists: pgsql-hackers, pgsql-general 
Am 19.07.22 um 00:18 schrieb Tom Lane:
> 
> Independently of the dimensionality question --- I'd imagined that
> array_sample would select a random subset of the array elements
> but keep their order intact.  If you want the behavior shown
> above, you can do array_shuffle(array_sample(...)).  But if we
> randomize it, and that's not what the user wanted, she has no
> recourse.
> 
> Now, if you're convinced that the set of people wanting
> sampling-without-shuffling is the empty set, then making everybody
> else call two functions is a loser.  But I'm not convinced.
> At the least, I'd like to see the argument made why nobody
> would want that.
> 

On the contrary! I am pretty sure there are people out there wanting 
sampling-without-shuffling. I will think about that.

Commits

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

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