WITH tbl AS
(SELECT table_schema,
TABLE_NAME
FROM information_schema.tables
WHERE TABLE_NAME not like 'pg_%'
AND table_schema not in ('information_schema'))
SELECT table_schema,
TABLE_NAME,
(xpath('/row/c/text()', query_to_xml(format('select count(*) as c from %I.%I', table_schema, TABLE_NAME), FALSE, TRUE, '')))[1]::text::int AS rows_n
FROM tbl
ORDER BY rows_n DESC;