| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Martin Kalcher <martin(dot)kalcher(at)aboutsource(dot)net>, Robert Haas <robertmhaas(at)gmail(dot)com>, John Naylor <john(dot)naylor(at)enterprisedb(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: [PATCH] Introduce array_shuffle() and array_sample() |
| Date: | 2022-07-18 22:32:00 |
| Message-ID: | CAKFQuwZ9o3Nw5TVgPf9xeTc73ad=BYJjT9werq6ztp6Lb_FVHA@mail.gmail.com |
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| Lists: | pgsql-general pgsql-hackers |
On Mon, Jul 18, 2022 at 3:18 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> 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.
>
>
And for those that want to know in what order those elements were chosen
they have no recourse in the other setup.
I really think this function needs to grow an algorithm argument that can
be used to specify stuff like ordering, replacement/without-replacement,
etc...just some enums separated by commas that can be added to the call.
David J.
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