Alexander Farber <alexander.farber@gmail.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
