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>, Robert Haas <robertmhaas@gmail.com>
Cc: 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: 2022-07-19T20:20:57Z
Lists: pgsql-hackers, pgsql-general

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Am 19.07.22 um 16:20 schrieb Tom Lane:
> 
> So I withdraw my original position.  These functions should just
> shuffle or select in the array's first dimension, preserving
> subarrays.  Or else be lazy and reject more-than-one-D arrays;
> but it's probably not that hard to handle them.
> 

Here is a patch with dimension aware array_shuffle() and array_sample().

If you think array_flatten() is desirable, i can take a look at it. 
Maybe a second parameter would be nice to specify the target dimension:

   select array_flatten(array[[[1,2],[3,4]],[[5,6],[7,8]]], 1);
   -------------------
    {1,2,3,4,5,6,7,8}

   select array_flatten(array[[[1,2],[3,4]],[[5,6],[7,8]]], 2);
   -----------------------
    {{1,2,3,4},{5,6,7,8}}

Martin

Commits

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

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