Spatial join very slow?

[bertt]

Hi,

I'm executing the following query on a 147K world city points table (loaded parquet file from https://public.opendatasoft.com/explore/dataset/geonames-all-cities-with-a-population-1000/export/?disjunctive.cou_name_en&sort=name)

Find pairs of cities that are within 5 degrees (about 555 km) of each other.

but it ?never? finishes (v1.1.1 ) :-( PostGIS is ready within a second...

SELECT
    a.name AS city_a,
    b.name AS city_b,
    ST_Distance(
        a.coordinates,
        b.coordinates
    ) AS distance_degrees
FROM cities a
JOIN cities b ON a.geoname_id <> b.geoname_id
WHERE ST_Distance(
    a.coordinates,
    b.coordinates
) <= 5; -- Distance in degrees