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

On 2022-07-19 Tu 07:15, Martin Kalcher wrote:
> Am 18.07.22 um 23:48 schrieb Martin Kalcher:
>>
>> If we go with (1) array_shuffle() and array_sample() should shuffle
>> each element individually and always return a one-dimensional array.
>>
>>    select array_shuffle('{{1,2},{3,4},{5,6}}');
>>    -----------
>>     {1,4,3,5,6,2}
>>
>>    select array_sample('{{1,2},{3,4},{5,6}}', 3);
>>    ----------
>>     {1,4,3}
>>
>> If we go with (2) both functions should only operate on the first
>> dimension and shuffle whole subarrays and keep the dimensions intact.
>>
>>    select array_shuffle('{{1,2},{3,4},{5,6}}');
>>    ---------------------
>>     {{3,4},{1,2},{5,6}}
>>
>>    select array_sample('{{1,2},{3,4},{5,6}}', 2);
>>    ---------------
>>     {{3,4},{1,2}}
>>
>
> Having thought about it, i would go with (2). It gives the user the
> ability to decide wether or not array-of-arrays behavior is desired.
> If he wants the behavior of (1) he can flatten the array before
> applying array_shuffle(). Unfortunately there is no array_flatten()
> function (at the moment) and the user would have to work around it
> with unnest() and array_agg().
>
>


Why not have an optional second parameter for array_shuffle that
indicates whether or not to flatten? e.g. array_shuffle(my_array,
flatten => true)


cheers


andrew

--
Andrew Dunstan
EDB: https://www.enterprisedb.com