Re: Sort functions with specialized comparators

> On 7 Jan 2025, at 09:43, John Naylor <johncnaylorls@gmail.com> wrote:
>
>> With the same setup as in the first message of this thread we can do:
>>
>> postgres=# SELECT _int_contains(arr,ARRAY[1]) FROM arrays_to_sort;
>>
>> before patch patch
>> Time: 567.928 ms
>> after patch
>> Time: 890.297 ms
>> timing of this function is dominated by PREPAREARR(a);
>>
>> What bothers me is that PREPAREARR(a); is returning new array in case of empty input. That's why I considered little
refactoringof resize_intArrayType(): reorder cases so that if (num == ARRNELEMS(a)) was first. 
>
> Hmm, I'm confused. First, none of the arrays are empty that I can see
> -- am I missing something?

Ugh...sorry, I posted very confusing results. For starters, I swapped "patched" and "unpatched" results. So results
showclear improvement in default case. 

I'm worried about another case that we cannot measure: PREPAREARR(a) on empty array will return new array.

And one more case.
BTW for pre-sorted desc arrays desc sorting is slower:
postgres=# CREATE TABLE arrays_sorted_desc AS
    SELECT a arr
        FROM
        (SELECT ARRAY(SELECT -i from generate_series(1, 1000000)i) a),
         generate_series(1, 10);
SELECT 10
Time: 707.016 ms
postgres=# SELECT (sort_desc(arr))[0] FROM arrays_sorted_desc;
Time: 41.874 ms

but with a patch
postgres=# SELECT (sort_desc(arr))[0] FROM arrays_sorted_desc;
Time: 166.837 ms


Best regards, Andrey Borodin.