Re: [PATCH] Introduce array_shuffle() and array_sample() - Mailing list pgsql-hackers

Hi all,

reading this blog post https://www.depesz.com/2023/04/18/waiting-for-postgresql-16-add-array_sample-and-array_shuffle-functions/ I became aware of the new feature and had a look at it and the commit https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=888f2ea0a81ff171087bdd1c5c1eeda3b78d73d4

To me the description

   /*
    * Shuffle array using Fisher-Yates algorithm.  Scan the array and swap
    * current item (nelm datums starting at ielms) with a randomly chosen
    * later item (nelm datums starting at jelms) in each iteration.  We can
    * stop once we've done n iterations; then first n items are the result.
    */

seems wrong. For n = 1 the returned item could never be the 1st item of the array (see "randomly chosen later item").

If this really is the case then the result is not really random. But to me it seems j later can be 0 (making it not really "later"), so this might only be a documentation issue.

Best regards

Salek Talangi