Re: general purpose array_sort

On Sat, Sep 28, 2024 at 10:41 PM jian he <jian(dot)universality(at)gmail(dot)com> wrote:
>
> On Sat, Sep 28, 2024 at 7:52 PM Junwang Zhao <zhjwpku(at)gmail(dot)com> wrote:
> >
> > PFA v2, use COLLATE keyword to supply the collation suggested by
> > Andreas offlist.
> >
> this is better. otherwise we need extra care to handle case like:
> SELECT array_sort('{1,3,5,2,4,6}'::int[] COLLATE "pg_c_utf8");
>
>
> + <row>
> + <entry role="func_table_entry"><para role="func_signature">
> + <indexterm>
> + <primary>array_sort</primary>
> + </indexterm>
> + <function>array_sort</function> ( <type>anyarray</type>
> <optional>, <parameter>dir</parameter> </optional>)
> + <returnvalue>anyarray</returnvalue>
> + </para>
> + <para>
> + Sorts the array in either ascending or descending order.
> + <parameter>dir</parameter> must be <literal>asc</literal>
> + or <literal>desc</literal>. The array must be empty or one-dimensional.
> + </para>
> + <para>
> + <literal>array_sort(ARRAY[1,2,5,6,3,4])</literal>
> + <returnvalue>{1,2,3,4,5,6}</returnvalue>
> + </para></entry>
> + </row>
> I am confused with <parameter>dir</parameter>. I guess you want to say
> "direction"
> But here, I think <parameter>sort_asc</parameter> would be more appropriate?

This doc is mostly copied and edited from intarray.sgml sort part.

And the logic is basically the same, you can check the intarray module.

>
>
> <parameter>dir</parameter> can have only two potential values, make it
> as a boolean would be more easier?
> you didn't mention information: "by default, it will sort by
> ascending order; the sort collation by default is using the array
> element type's collation"
>
> tuplesort_begin_datum can do null-first, null-last, so the
> one-dimension array can allow null values.

The following(create extension intarry first) will give an error, I
keep the same for array_sort.

SELECT sort('{1234234,-30,234234, null}');

>
> Based on the above and others, I did some refactoring, feel free to take it.
> my changes, changed the function signature, so you need to pay
> attention to sql test file.

Thanks for your refactor, I will take some in the next version.

--
Regards
Junwang Zhao