Re: How to pass a list of locations (longitude, latitude) to a PostgreSQL/PostGIS stored function?

On Tue, 25 Mar 2025 at 19:07, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Alexander Farber <alexander(dot)farber(at)gmail(dot)com> writes:
> > Then I am trying to add a function, which would receive a series of
> > locations (longitude and latitude pairs in microdegrees) and return a
> list
> > of lowercase 2-letter country codes, like "de", "pl", "lv":
>
> > CREATE OR REPLACE FUNCTION find_countries(locations BIGINT[][])
> > RETURNS TABLE (country TEXT) AS $$
>
> Postgres isn't too friendly to representing a list of locations as
> a 2-D array, because we generally don't treat arrays as being
> arrays-of-arrays, so unnest produces a set of bigints not a set
> of smaller arrays. You might be best advised to create a composite
> type like "location (long bigint, lat bigint)" and use an array of
> that. If you're really hot to use a 2-D array, the only construct
> I can think of that's on board with unnesting that the way you need
> is plpgsql's FOREACH SLICE syntax:
>
>
> https://www.postgresql.org/docs/devel/plpgsql-control-structures.html#PLPGSQL-FOREACH-ARRAY
>
> You could probably make a custom version of unnest that uses that
> and then keep your query about the same.
>
> regards, tom lane
>
>
>
Another approach I use is to string everything into a JSON object, and
de-serialize it in the function.